## Automatic LED Emergency Light-Modified Version

As there is serious discussions going on about our previous Automatic LED Emergency Light Circuit using LM 317, Mr.Seetharaman has come up with a modified version of the same which answers many of the doubts raised in our Comments section.

Note: Mr.Seetharaman has developed a new version of Automatic LED emergency light. This one is more simple,more efficient and uses minimum components. Take a look: Simple Emergency Lamp Circuit

Here follows Seetharaman’s Description about the Modified Automatic LED Emergency Light using LM 317.

Dear John
Since there were lots of doubts from our readers on the LED emergency light, I have written a detailed letter to two of our readers. Of course few modifications are required, which I have indicated on the drawings and on calculations how I arrived at it.  I thought of enclosing it to you so that it can be kept in some library of our site for any ones reference. For each circuit we can have a similar detailed theory, may not be with all calculation, just general operation theory of each part of the circuit. You may think of it. As a first feed back I am sending this.  I have a feeling that most of the people would have made the mistake in base emitter of BD140, the lead out are against normal convention.

To understand the above circuit in a better way, it can be divided into two parts.

1. LED lamp circuit
2. The Battery charger circuit

### LED Lamp circuit

1. All are white hi bright LEDs rated for 3Volt @ 25mA
2. The total current requirement is 12 X 25 = 300mA
3. This current has to flow through T2 – BD140 PNP transistor
4. The minimum current gain (hfe) of this transistor @ 500mA is 50
5. Hence the base current Ib requirement is Ic / hfe, 300 / 50 = 6mA
6. Base emitter drop of T2 at 500mA is 0.77 volt
7. With the fully charged battery at 6.9volt terminal voltage (for cycle operation use) the voltage available across the new bias resistance is (6.9 – 0.77)
8. Hence the bias resistance is = 6.13 / 6 = 1000ohms
9. As the battery drains the final terminal voltage will be 5.4volt
10. The bias resistance will be (5.4 – 0.77) /  6 = 770 ohms Hence a 680 ohms was preferred for bias resistance with drained battery also it will give enough brightness.
11. The very important information about BD140 is, as you view the pins, metal portion of the transistor facing down left is emitter centre collector and right is base. Most of the constructors make this mistake, relying on the convention that left base and right emitter. If you have made this mistake please correct it.

Once this portion is checked for reliable operation we will proceed to charger portion.

### The Battery charger circuit

1. The battery requires a full terminal voltage of 6.9V at this point charger should cut off.
2. That is the voltage across the chain ZD1, R2 and T1 be should be 6.9 volt
3. T1 be voltage of 0.7 volt plus drop across R2 and zener voltage should be 6.9V
4. T1 be current = Ic / hfe
5. Ic is 1.25 / 180 = 7mA
6. Ibe = Ic / hfe of T1  i.e = 7 / 70 = 100uA
7. Drop across R2  =1.2 X .1 mA = 0.12volt
8. Hence Zener voltage = 6.9 – (0.7 + 0.12) = 6.08 the near by preferred zener voltage is 6.2 volt
9. Say the battery voltage at full charge will be 7 volt with 6.2 volt zener diode
10. To calculate R16 value for charging at 1 /10 th of the rated current of the battery 4.5AH / 10 = 450mAH
11. Transformer 9volt AC the voltage across C1 will be 9 X 1.414 = 12.6 volt
12. The drop across LM317 at 450mA current for good regulation is 3volt
13. The drop across protective diode D5 is 0.7 volt.
14. The  voltage available at cathode of D5 is 12.6 – (3+0.7) = 8.9volt
15. The battery after fair discharge will be at 6 volt
16. Hence R16 = (8.9 – 7) / 0.45 = 6 ohms
17. The nearby standard value for operation is 5 ohms.
18. At the end point of battery 5.4 volt the maximum charging current can be of (8.9 – 5.4) / 5 = 0.7 amps well within the higher charging limit of the battery.
19. With this circuit over night the battery will get charged fully.
20. Over charging is taken care and protected by T1

Hope with the above guide line you can make your light work successfully.

## More Modification!!!

### Automatic LED Emergency Light with Under Voltage Cut Off Protection:

Mr. Seetharaman has further modified this LED Emergency Light with an under voltage cut-off protection to protect battery from deep discharge. Once the battery terminal voltage falls below 5.7 volts the LEDs will be switched off. Take a look at the modified circuit shown below.

To understand the above circuit in a better way, it can be divided into two parts.

1. LED lamp circuit
2. The Battery charger circuit

LED Lamp circuit

1. All are white hi bright LEDs rated for 3Volt @ 25mA
2. The total current requirement is 12 X 25 = 300mA
3. This current has to flow through T2 – BD140 PNP transistor
4. The minimum current gain (hfe) of this transistor @ 500mA is 50
5. Hence the base current Ib requirement is Ic / hfe, 300 / 50 = 6mA
6. Base emitter drop of T2 at 500mA is 0.77 volt
7. With the fully charged battery at 6.9volt terminal voltage (for cycle operation use) the voltage available across the new bias resistance is (6.9 – 0.77)
8. Hence the bias resistance is = 6.13 / 6 = 1000ohms
9. As the battery drains the final terminal voltage will be 5.4volt
10. The bias resistance will be (5.4 – 0.77) /  6 = 770 ohms Hence a 680 ohms was preferred for bias resistance with drained battery also it will give enough brightness.
11. The very important information about BD140 is, as you view the pins, metal portion of the transistor facing down left is emitter centre collector and right is base. Most of the constructors make this mistake, relying on the convention that left base and right emitter. If you have made this mistake please correct it.
Once this portion is checked for reliable operation we will proceed to charger portion.
1. The battery requires a full terminal voltage of 6.9V at this point charger should cut off.
2. That is the voltage across the chain ZD1, R2 and T1 be should be 6.9 volt
3. T1 be voltage of 0.7 volt plus drop across R2 and zener voltage should be 6.9V
4. T1 be current = Ic / hfe
5. Ic is 1.25 / 180 = 7mA
6. Ibe = Ic / hfe of T1  i.e = 7 / 70 = 100uA
7. Drop across R2  =1.2 X .1 mA = 0.12volt
8. Hence Zener voltage = 6.9 – (0.7 + 0.12) = 6.08 the near by preferred zener voltage is 6.2 volt
9. Say the battery voltage at full charge will be 7 volt with 6.2 volt zener diode
10. To calculate R16 value for charging at 1 /10 th of the rated current of the battery 4.5AH / 10 = 450mAH
11. Transformer 9volt AC the voltage across C1 will be 9 X 1.414 = 12.6 volt
12. The drop across LM317 at 450mA current for good regulation is 3volt
13. The drop across protective diode D5 is 0.7 volt.
14. The  voltage available at cathode of D5 is 12.6 – (3+0.7) = 8.9volt
15. The battery after fair discharge will be at 6 volt
16. Hence R16 = (8.9 – 7) / 0.45 = 6 ohms
17. The nearby standard value for operation is 5 ohms.
18. At the end point of battery 5.4 volt the maximum charging current can be of (8.9 – 5.4) / 5 = 0.7 amps well within the higher charging limit of the battery.
19. With this circuit over night the battery will get charged fully.
20. Over charging is taken care and protected by T1

Hope with the above guide line you can make your light work successfully.

Custom Search

### 522 Responses to “Automatic LED Emergency Light-Modified Version”

• Naveen kunar says:

sir i want use 12 volt 6ah lead acid battery. please tell me neccesary changes in charging circuit

• april verdeflor says:

i hope you will make a step by step video on how you make an automatic LED emergency light. it would be a great help for beginners like me. thank you.

• alireza says:

Hi, I am an Iranian and I am so glad that I met you guys.
Your best and most complete website is in electronics education for children.

• pranajit says:

Sir,
can you please upload the PCB for Automatic LED Emergency Light with Under Voltage Cut Off Protection circuit.
Thanks

• Seetharaman says:

It is already given in simple emergency lamp circuit. The PCB is with all improvements.

• auto circuit giagram of emergency light

• Seetharaman says:

This is the auto circuit diagram when the mains supply is on the battery will get charged and when mains power fail the LEDs will turn on automatically.

• D.Bashyam says:

Hi,
very interesting subjects and projects,keep it up.We find almost all circuits invariably has a transformer but designing such transformers are not provided. can you forward me with such reference or the data sheet for 10Va-100/200Va design.
bashyam

• TANMAY says:

sir, 1. i did not understand that how the led near the potentiometer determines that battery is getting charged.
2. i did not understand the fifth step in the battery charger circuit.

• Seetharaman says:

When the battery s charging the IC output voltage will be 6.9 or more depends on the current flow to battery. once the charge is full the terminal voltage will reach 6.9volt or more the T1 transistor will conduct to bypass the reference current through R1 180 ohms. the current through it is reference voltage between pin no 2 & 1 of the IC which 1.25 volt and the resistance is 180 ohms hence the current through R1 is 7mA. this is the current T1 to bypass hence in the next step what is the T1 base current required 7 ma / hfe of T1 which is 70 etc etc.

• Vivek verma says:

How to build this circuit using 50 LED’s?

• hui wijaya says:

hii. i ve just build this circuit with the absent of 4.7ohm near diode 1n4007 … and i need 7.47v at the output diode to cutoff voltage(led on the emitter and collector of bc548 to turn off) .. could we make it more low voltage needed to cutoff and where i m wrong?is the resistor 4.7 ohm missing so the circuit goes wrong?

• Seetharaman says:

Hi first disconnect over voltage protection circuit ZD1 R2 and T1. Now adjust VR1 for the required output voltage without connecting battery. The resistance 4.7 ohms is the charging current limiting resistance kindly do not delete. Now connect the battery and check the current flow to battery by measuring the voltage drop across 4.7 ohms. If you want higher charging current reduce the value to 2.2 ohms

• lester musca says:

How to write an circuit operation in this example and circuit application. Please help me to do this.. RIchard.

• Vivek verma says:

Modify the current version with new implementation like
1.Touch dimmer circuit,
2.Battery over charging protection,
3.60 LED’s setup,
4.Battery low indicator with buzzer.

• Vivek verma says:

Hello sir, i have succeeded in making automatic emergency light using 12 LED’s but unsuccessful while using 50 LED’s, i kindly request you to help me out while making automatic emergency light using 50 LED’s. Please upload a circuit description of automatic emergency light using 50 LED’s.

• Imron Zarkasyi says:

I’ve succeeded with this circuit, but I still need one more modification on it. It is how to embed a night-activated function so that the LEDs are not glowing at the absence of mains power in the day light. Can you give me a brief explanation or a schematic of combining these circuits? thanks.

• Seetharaman says:

Please check the pin connections of LM317 it is not similar to 78XX series. and correct it it will become alright.

• Assam Butt says:

Assam Butt

Dear Respected Seetharam,

i have been working on this circuit since two weeks and facing only one problem again and again,

1. the charging circuit is not working properly, as LM317 is not giving regulated voltage, if i disconnect the circuit right after the LM317, it shows a potential difference of 8~9v DC between gnd and output pin of regulator(not stable). if i remove the Resistor R1 and then measure the voltage across ZD1 it gives me 6.2V DC. furthermore, i think in my circuit T1 is not switching with R1(180ohm) i replaced the resistor with a variable resistance and then tried to adjust it with circuit “ON”
at an instance when it reached only 10ohm circuit led’s started to glow fully. at that time i measured the voltage across ZD1 and adjusted with VR1 at 6.9v DC (without battery connected).
but after some seconds i felt smell and then VR1 gave a flash and gone bad.
Please guide me should i change any resistor value or put exactly the same components?
secondly, we cannot get the transistor of same hfe from market do it have any effect on the circuit or resistor?
Kindly Help me out from this scenario.
Thanks and Regards,

• Yumna says:

Dear Sir
I have made this circuit i am not getting 3volts at the output of LM317 this way the battery wont charge. Please help me!

• Yumna says:

Hello Sir,
What changes will I have to do in the circuit if i want to use 4.8V 2.7Ah rechargeable battery? Please help! Thank you.

• nikita says:

Sir,Is transformer used for charging purpose in Automatic LED Emergency Light?

• rajeev kumar says:

yes you don’t beleave in transformer than you use now

• Arun kumar says:

iam not charging in battery. disconnected the battery check out voltage 6.2

• Arun kumar says:

iam this circuit ready iam connected battery not charging.

• Sachin says:

Sir this ckt not working plz help me i selected this for hobby project

• rajeev kumar says:

you try again for making with concentrate because my ckt is starting work ok

• Andy says:

Hi Seetharaman.

I try to make this under voltage cutoff circuit. But it don’t work.
Try to replace 5.1v to 5.6v zener, BC547 to BC337, 560R resistor to 1k…etc…still does not work.

With extra under voltage cut-off protection circuit, when I plugging the power source, the light will not turn off, when battery discharge down to 5.1v, lights not cut-off. I think this extra circuit will never work.

You’ve ever tried to make this circuit yet?

• seetharaman says:

Hi Andy it is tried practically. with higher gain pnp transistor for BD140 similar to S8550 I ahd a problem of light glowing low with mains on hence R15 was reduced to 330 ohms. otherwise it is working fine at my home.

• Andy says:

Hi seetharaman.
Reduce R15 down to 330R is working, thanks for help.
But cut-off protection dont work, any suggestion ?

• Arpan says:

I have wired the “Automatic LED Emergency Light with Under Voltage Cut Off Protection” circuit .I used 15v transformer.I removed the led which indicates charging. but when the value of VR1 is kept at the highest i only get a voltage drop of 6.5v between gnd. if I use 6.5 volts to charge this battery, will battery ever reach 6.9V which is higher than reacharging voltage?I found that the battery has never been fully charged, furthermore the maximum output voltage is only 6.5v (battery disconnected).I tried to replace the D1 with the new ones many times but it still showed the same thing. I even replaced the T1 BC548 but nothing changed.what should i do?

• Seetharaman says:

Hi Arpan replace VR1 with 4.7K. by disconnecting battery and T1 chech and set the output voltage to 6.9 volts with VR1. Then connect battery etc.

• Arpan says:

Then how it protect the battery from overcharge if I remove T1 .I also used 4.7k and more but the output voltage is not exceed 6.5v in presence of zener diode.

• seetharaman says:

For protecting the battery constant voltage is important plus the maximum current. current is taken care by IC charecterestic itself will limit to 1.5A max. the voltage by VR1 which sets the the output voltage to 6.9volt. the zener is only a backup protection in the event of potentiometer failure over a period of time.

• Andy says:

Arpan.
Try replace R1 180R to 120R.

• chinmay says:

how to give heat sink to LM317 and BD140 and have u tried this circuit… ??

• Zildjian says:

Hi sir, i need help. the led indicator wont light. it only lights when i remove the battery from the circuit. one more thing i dont think that my battery is charging cause i only get 5.8v in the battery terminal without the battery.

many thanks

• Seetharaman says:

HI Zild you kindly check the 317 output voltage with LED indication and also without it. without LED if it becomes OK, replace LED with high efficiency 3mm red LED which requires only 2 to 3mA for brightness.

• siri says:

6v 4.5ah means?

• Seetharaman says:

Hi Siri 6volt is the battery terminal potential difference.(the voltage available for your use). mAH is ampere hour rating of the battery. in simpler words 4.5 AH 20 hours rating means, If you discharge at a current rating of 225mA the battery will sully the load for 20hours. For easy under standing, it is the product of the current the battery can supply in Amps for so many hours. If you draw 450mA from a fully charged battery, it will supply this current for 10hrs approximately. please go through the following link.
http://www.dcbattery.com/faq.html

Hello sir
I too have a requirement to modify this circuit to work with a 12v 7AH battery. What modification is required to drive a 1W single or double LED?

regds

• abhi says:

hi sir
i made the circuit for 9v dc battery and have changed the zener diode D1 to 9v and D2 to 8v
but it doesn’t work so what all modification do i need
plz help

i need modification for 9v dc battery what all things do i need to change

• Andy says:

Hi abhi.
What type your 9V battery ? yr battery is Nicad, NiMH, Lion or sealed lead acid ?
Remember, this circuit is only used with sealed lead acid battery.

• Andy says:

To charge 12v battery, V charge=13.8V, the power source at least: 13.8v+3v+0.7v=17.5v, choose 18v source minimum.

ZD1= 13.8v-(0.7+0.12)= 12.98v, choose 1N4743A 13v zener.

To calculate R16 value for charging at 1/10th of the rated current of the battery 7AH/10=0.7AH. Because voltage reference of LM317 is Vout-Vadj=1.25v, R16=(1.25+0.7)/0.7=2.78R, choose 2.7ohm 5w resistor.

For safety discharge battery under 10v, choose ZD2=10v zener 1N4740A.

Depend what type of Led, u can use formula to calcutale resistor limit: R=(Vbattery – Vled)/Aled, example if ur led working with 5v/50mA: 12v-5v/0.05=140ohm.

• Rohit says:

Sir, if we use 6.2 volts to charge this battery even with over charging, will battery ever reach 6.9V which is higher than reacharging voltage?

• Amit Sharma says:

Dear Sir,
Can this circuit be modified for 20-24W, using 12V-7.5AH battery.
what modifications are required when we use 3W or 5W power leds.
I need it for my farm at my village place, as we have 14 hrs of power cut daily.

Dear Brother, i first disconnect ZD1 and set the required voltage correctly 6.999v through POT as desired. then i reconnect the Zener ZD1 and desired voltage remain the same. But i am facing LOW CURRENT FLOW issue, when i omitt the diode D5 the current flows as desired but when i connect D5 the current the reduces to only 20mA and at that time the voltage of the battery is 6.2v, i aslo changed D5 (i.e 1N4007) but all in vain. At such stage the current flow should be atleast 100mA which is not the case. Please sir, make me correct i am making a mistake somewhere in the circuit…..Thanks….Regard

• Linnet says:

Hi sir,urgently want keil codes for developing a color-panel on touchscreen LCD. Im using ARM7 LPC2148 processor.

Thanks!

• RAJIB BANERJEE says:

Respected ,Seetharaman Sir,
I need a good circuit witch will fit any Regular Inverter from outside as a device,and this will working as a hybrid solar inverter, will function as a junction box of the solar pannel unit for charing the existing batery of that inverter and if not charging from solar properly then convert the charging line to the ac mains for full charge of that battery.
If this possible,then send my mail,Thanks.Rajib

• Assam Butt says:

Assam Butt
January 10, 2013 at 10:04 pm

Dear Respected Seetharam,

i have been working on this circuit since two weeks and facing only one problem again and again,

1. the charging circuit is not working properly, as LM317 is not giving regulated voltage, if i disconnect the circuit right after the LM317, it shows a potential difference of 8~9v DC between gnd and output pin of regulator(not stable). if i remove the Resistor R1 and then measure the voltage across ZD1 it gives me 6.2V DC. furthermore, i think in my circuit T1 is not switching with R1(180ohm) i replaced the resistor with a variable resistance and then tried to adjust it with circuit “ON”
at an instance when it reached only 10ohm circuit led’s started to glow fully. at that time i measured the voltage across ZD1 and adjusted with VR1 at 6.9v DC (without battery connected).
but after some seconds i felt smell and then VR1 gave a flash and gone bad.
Please guide me should i change any resistor value or put exactly the same components?
secondly, we cannot get the transistor of same hfe from market do it have any effect on the circuit or resistor?
Kindly Help me out from this scenario.
Thanks and Regards,

• Vivek says:

Dear Seetharaman Sir

Firstly, i would like to extend my sincere appreciation for the wonderful work that you and this site are doing.

I want to manufacture a few complex circuit for use at home and would like to know how i can contact you personally. I have a flow diagram and know how the system should function but i do not know how to bring it into practical use since i am not strong in electronics. I would really appreciate a mail from you in this regard. Thank you in advance

• [...] 3. Modified Version of Automatic LED Emergency Lamp using LM 317 [...]

• dilip says:

how we can convert 7v to 1.5v?

• SISON says:

respected sir,
AFTER SHOWERING OF TOO MUCH COMMENTS NEED ITS TIME TO MODIFIED
YOUR CIRCUIT AGAIN.BCZ ITS DIFFICULT TO READ 400 COMMENTS.ALSO I WOULD LIKE TO NOTE THAT EVEN AFTER 4 VOLT IN BATTERY STILL DEEP DISCHARGE NOT WORKING.ALSO BATTERY TERMINAL VOLTAGE NEVER REACH ATLEAST 6.9V.

SISON.C.S
ALWAHDA MALL
ABUDHABI
UAE
MOB–00971559265523
PHONE KERALA-9747447168(NOW AVAILABLE INDIA)

• please send the details of the topic ANTI-PETROL THEFT ALARM .YOUR SITE IS PROVIDING A LOT OF HELP TO US

• Biju says:

Sir,
I have one doubt about the battery charger part of the circuit. Is it possible to get 400mA at 8V considering the diode D5 forward resistance of few hundred ohms added to circuit?(I’m getting only 40mA at the output at 8V)
At my place the supply voltage is about 170 to 190 V during most of the times, so do i need to change the transformer?

• Seetharaman says:

Hi Biju use a 12 volt transformer, this should take care and use a good heat sink for LM317 regulator IC.

• Assam Butt says:

Dear Respected Seetharam,

i have been working on this circuit since two weeks and facing only one problem again and again,

1. the charging circuit is not working properly, as LM317 is not giving regulated voltage, if i disconnect the circuit right after the LM317, it shows a potential difference of 8~9v DC between gnd and output pin of regulator(not stable). if i remove the Resistor R1 and then measure the voltage across ZD1 it gives me 6.2V DC. furthermore, i think in my circuit T1 is not switching with R1(180ohm) i replaced the resistor with a variable resistance and then tried to adjust it with circuit “ON”
at an instance when it reached only 10ohm circuit led’s started to glow fully. at that time i measured the voltage across ZD1 and adjusted with VR1 at 6.9v DC (without battery connected).
but after some seconds i felt smell and then VR1 gave a flash and gone bad.
Please guide me should i change any resistor value or put exactly the same components?
secondly, we cannot get the transistor of same hfe from market do it have any effect on the circuit or resistor?
Kindly Help me out from this scenario.
Thanks and Regards,

• surbhi says:

sir,what are the basic requirements for implimenting this circuit.i just want to know “how to start” and what are the basic electronics kit requirement????????????

• Imron says:

I found that the battery has never been fully charged, furthermore the maximum output voltage is only 6.4v (battery disconnected). When I took out the T1 BC548, the output voltage was 9v. As you said, in the previous comments, that it’s due to the defected D1 zener 6.2v 0.5w. I tried to replace the D1 with the new ones many times but it still showed the same thing. I even replaced the T1 BC548 but nothing changed.
I also need to know how many sets (BD140+12 LEDs) can be supplied by this circuit? Can I use 5 or 6 sets?

• Seetharaman says:

Hi Imron use a 6.8 volt zener. With 5 sets the battery charge will last for 2 to 2 1/2 hrs. with 6 sets it will last for around 1 1/2 to 2 hrs.

• Imron says:

Thanks for the circuit. I’ve tried it and it worked perfectly. But there is something I don’t understand, It’s how to adjust the VR1. The red LED glows all the time and I’m just worried that the battery is over charged. Would you please give me a brief explanation on how to correctly adjust the VR1 so that I am sure that the battery is not charged all the time but stops when it’s already fully charged. Thanks.

• vignesh says:

whether collector of t2 is connected to battery or emitter…..thank you i advance isr

• Seetharaman says:

Hi Vignesh It is a PNP transistor and hence emitter is connected to positive of the battery,

• sibi says:

Hi

Can we use PWM circuit using 555 to extend the working time?
So the LED wont be on all the time, but due to persistence of vision we can see continuous light.How much improvement can we expect with that?

• Deepak says:

Mr.Seetharaman, your circuit is really good. Can you help me in modifying the circuit, so that we can add two more led lights in series to all the leds. This will result in high power light output. Pls reply to mail with the circuit. Thanks.

• vignesh says:

respected sir
i wish to know how the transistor ll cut off the battery charging when it exceeds 6.9v…..thank you in advance

• Jotham says:

hello, sir. I have a 12v 12ah Battery and i want to use “12v 10w rounded Fluorescent tube”…( like car’s ones )
i need 2 link 3 pieces of this Fluorescent tube.
so, i want 2 know the new modifications for that circuit which are related to :
1-the suitable Transformer (volt and ampere)
2-ZDs (volts and watts)
3-BD140
4-LM317
5-the other components.
6-for how many hours will the lighting keep on in full-charging case ?

• Jotham says:

hello, sir. I have a 12v 12ah Battery…what if i want to use a “12v 10w rounded fluorescent (like cars’ ones)”
what modifications should i perform on
1-Transformer
2-ZDs
3-BD140
4-LM317
5-other components.
and for how many hours will it keep ON lighting in full charging case?
Regards,

• Rajib Chowdhury says:

Respected Sir,
I want to add one more feature to your circuit, the leds should be controlled with an ir remote,how can I make such a modification to your circuit ? If possible please refer some websites from where I can perform these modifications.
Thank you.

• Muthukrishnan says:

Respected sir,
I was tried so many times sir,but battery discharging circuit not working sir i used 5.1 v znr but below 4 volt also led continuously glowing sir…i checked the component everything correct.but deep discharging not function sir.automatically switching and every thing is good sir next what can i do please explain me sir my mail id Krishna198023@gmail.com Help me sir.

thank you

• joshua keen says:

hi sir seetharaman

im currently using ur circuit here but cant seem to find a way to make it work, i modified it with my own specification… heres what i modified recently…

-instead of 12 led i used 24 leds
-replaced the battery to 12v with 7.2ah ( supposed to be 7.5ah but cant seem to find one in our place)

sir i tried using ur original circuit in multisim v11 but the LED indicator for charging doesnt work.. i also tried to put a voltmeter in parallel to the battery to see if its charging but seems to me that its not

with ur current skills maybe u could put me in the right direction, thank you very much for ur help

• angelie says:

• Shankar Varma says:

the voltage across the cathode of ZD1 and gnd is only 6.4V. when i removed the battery and the zener ZD1 and made the voltage at the charging poing of the battery(which was the junction of ZD1 and 4.7 ohm ) as 7v. the voltage drops when i connect the zener and also the ZD1 is not conducting.

• seetharaman says:

Hi Shankar You disconnect ZD1 and battery. now measuring the output voltage going to battery for charging. set it for 6.9 volt DC now connect the battery check the voltage drop across R16 and calculate the current flowing with a flat battery it should be 500mA and partially charged battery it can be between 50 and 250mA. If this current is not available your LM317 pin connections are wrong or your transformer is not capable of 9 volt RMS at 500mA. check throughly. this is a proven circuit design.

• Shankar Varma says:

i also checked the voltage across zener when it is reverse biased , it is 6.2v. and the zener diode also works when connected to a 9v battery with 1k in series and in reverse bias , giving a voltage 0f 6.2v across it. i also checked the R1 and pot resistance. i have been trying this for many days now. please help.

• Shankar Varma says:

i did wire the circuit exactly as in figure. i find out that the zener is not concucting and the voltage over the zener changes when the value of VR1 is changed(when battery not connected).i have not connected the battery.and the potential difference with respect to the gnd at the cathode of zener, zd1 is max 0f 6.9 . when i remove the transistor T1 the output of LM317 is raised till 9v. I tried changing zener diode(6.2v 0.5w)many times but it does not get corrected.i also tried changing BC548, and LM317 . still i have the same problem. i find out that zd1 is not conducting in reverse bias when the battery is not connected.PLEASE HELP…PLEASE..

• Shankar Varma says:

i have wired the “Automatic LED Emergency Light with Under Voltage Cut Off Protection” circuit . the led which indicates charging has been glowing for more than 20 hours.. i dont know till what value the lm317′s output is to be adjusted. but when the value of VR1 is kept at the highest i only get a voltage drop of 6.64v betewwn gnd. what should i do?

• Vijay says:

Dear Mr Seetharaman,

I need to design a display using 5×7 matrix LED with certain light output specifications for commercial purpose. Can i contact you directly at your email id for assistance, if yes, give me your email id.

• Isaac says:

sir i have build a charging circuit that uses a BD 140 transistor to charge a 4.8 NiCd battery. Can i please know the operation of this transistor and also how can i calculate the taken for my battery to be fully charged and the time it will last when used. Thanks.

• Ahsan says:

i have tried this circuit with 2 1watt led in series and kept all the same but i have a problem that when the circuit is powered by battery it feedback some of voltage to regulator in my case nearly 5 volt and charging led lights. what should i am doing wrong any suggestion to me

• Seetharaman says:

Hi Srikanth add one more BD140 and 12 more LEDs with resistances
Hi Aswin you can use BD136 or BD138 or the present 8550

• samtoyn says:

hi sir, pls i need the block diagram of an automatic led emergency light pls its ujent sir.

• Aswin Jose says:

hey
I dont have BD140 available in stores… But BD136 is available… Any changes if i use that???

• min says:

hello mr.seeetharaman..this circuit design is very helpful for me..could u pls help me in making the same circuit but with more number of LEDs which is bright enough like a CFL lamp..is that possible? if so do i need to change any other component as well for this change? do pls help..
thank you very much..

• Srikanth says:

Sir,ur modified version of LED circuit working very well.I need to install atleast 24 nos LED.what are the changes in the value of other components..?

• Seetharaman says:

Hi Philips. Use 3nos AA rechargeable cells with limiting resistance per LED. or use a driver capable of 3.2 volts for an input of 2.2 to 2,64 volts. use a simple capacitance-rectifier-resistance charger circuit direct from mains for 1/12 of rated current of the cell.

• Philip Joy says:

hi the emergency lamp is working great- i now plan to make a rechargeable LED head lamp- it doesn’t need to be automatic- i intend to use a 3 volt hi bright LED and 2 AA size rechargeable cells to keep it light- it just need voltage regulation and over charge cut off- can you please help me sir?

• Siva Kumar says:

Dear Sir,
I have doubt sir. can i use the circuit for 30 LED’s parallel connection.
otherwise is there any changes required sir.what is the current gain for LM317.

• Sreejith Pillai says:

Thank You Sir.

• Seetharaman says:

Hi Pillai CFL requires around 110 volts at high frequency. If you want to convert it into an LED emergency light, except the battery and the switch remove all the other electronics available inside. replace them with the new assembled LED PCB. I prefer you to try the simple one appeared earlier use the following link.
http://www.circuitstoday.com/automatic-led-emergency-light#simple

• Sreejith Pillai says:

Dear Sir,

I have a working emergency cfl lamp.Can I replace the CFL lamp with say 10-20 leds? What are the required circuit modification for the same.From where should I tap the supply for the LEDs.Also how much voltage does a CFL require for working??

• Philip Joy says:

Thank You!!- PCB designed and fabricated- Going to assemble tomorrow !!

• Seetharaman says:

Hi use 2 in series and 3 of then in parallel it will be 900mA drain on the battery you will get around 5hrs of non stop lighting from a fully charged battery. (4500mAH / 900mA = 5H) Similarly you can calculate for other loads

• Setharaman says:

Hi Philipif you use 2 in series and 3 of then in parallel it will be 900mA drain on the battery you will get around 5hrs of non stop lighting from a fully charged battery. (4500mAH / 900mA = 5H) Similarly you can calculate for other loads

• jamshed says:

Dear Sir,

This relates to Fridge Door Alarm circuit and need your support as there might be no response at message sent at url of said circuit.

I have constructed above project on zero board and chekced all connections but used 22uf as 10uf was not available with me. circuit produces a very little sound and not a BEEP! no affect observed when LDR is brought to dark or light, pl help in finding error.

i also want to know, why a high value R3 (2.2M) and R4 (1M) are used, is it the reason??
thanks.

• Philip Joy says:

Sir, i forgot to ask max how many 300mA led’s can be connected in parallel? ie what is the max allowable current consumption?

• Sreejith Pillai says:

Dear Sir,

I have a working emergency cfl lamp.Can I replace the CFL lamp with say 10-20 leds? What are the required circuit modification for the same.From where should I tap the supply for the LEDs.Also how much voltage does the CFL require for working??

• Pratima says:

hey seetharaman i need the design and calculations of the battery charger circuit using scr..mine is a 12v,1.3Ah battery.
plz do help with the modifications also

• seetharaman says:

Hi Philip you can use, it will be a good power saver as no resistance is involved.

• Philip Joy says:

Sir, can we use 1 watt power LED’s for this circuit?
Forward Voltage:3.2V – 3.6V
Forward Current:300 mA

can we use two such LED’s series instead of LED and a resistor?

• seetharaman says:

Hi John if you are using 12 volt transformer. the DC will be 17volt battery requirement is 7volt a drop of 10 volt at 1amp is 10watts dissipation on LM317. you have to use a good heat sink. regarding 4.7 ohms resistance at 1amp it will generate 5 watts approximate hence you have to raise the rating to 10 watts. first set the output voltage without connecting to battery for 6.9 to 7.2volt then connect battery things should become alright.

• bilal says:

sir, i have problem in my emergency light charging power supply its only give 3.85 volts to battery what the problem sir i made 3 emergency light same circuit diagram but problem appeared in power supply its only give 3 to4 volts only i am thankful to you sir please reply regard to?

• Seetharaman says:

Hi Bilal By disconnecting T1 and charge indicating LED check regulator output voltage it should be 7volt if not check regulator IC pin connection it is not similar to 78XX series ICs. please refer to IC manual and connect , it should become alright. still if you have problem check the wiring fully. it is a proven circuit it should work ok.

• john says:

i use 12v amd 1amp transformer so the resistor of 5w getting hot .what is the changing required?
and what is the use of zener in this circuit…????? waiting for your reply…….

• Seetharaman says:

Alex kindly replace with 9 volt 1 amp good quality transformer.

• avinash says:

sir plz send on my gmail ID -full circuit of 40 watt inverter circuit with all information like, restance watt,tranformer coling volt,inductor etc plz telk me reply on my ID plz plz sir

• Alex says:

Hi,
I made the circuit and its working fine but,the transformer is getting hot.ie;i cannot hold my finger on transformer not more than 5 seconds.Is it the fault with transformer or the circuit?Please help

• Seetharaman says:

• john says:

i have many question regarding this led light
Q1:why we use zenor diode?
Q2:what is the use of bc548?
Q3:can we use diode bridge in this circuit?
Q4:how much leds will be connected in this circuit?
i m wating for your ans thanks………

• Q1. Ans: Zener diode is a active semiconductor device which has a heavily doped junction. It is always connected in reverse bias mode. It’s used to maintain a fixed voltage across, or in simple words, the zener diode is used to regulate voltage.

Q2. Ans: BC 548 is a npn transistor. It’s used in the circuit to regulate the charging of the battery along with the zener diode.

Q3. Ans: Yes you can use a i Amp bridge, or you can make a bridge using four IN4007 diodes.The scenario changes in case of implementation of center-taped transformer.

Q4. Ans: built another array of led’s with limiting resistors and use a driver transistor BD 140 !!!

Regards
Shiharan Choudhury
(R.F Engineer/professional electronic repairer)

• Seetharaman says:

Hi Davis no changes are required please proceed.

• Davis says:

Sir,will there be any difference if i use a 6v 10Ah battery in the same circuit?

• Seetharaman says:

Hi Shreyash when main supply is off it has to glow it is correct operation for the automatic emergency lamp. For your charging LED problem please refer my comments dated 13th April

• Shreyash says:

Sir,thank you for the circuit.But the problem for me is that when the main supply is off,the led’s still glow with the charging led still on.Help me out sir.I have to show this circuit tomorrow as my project

• Hi, charging LED can’t be on when mains is off. This is because, if you see the circuit, you will find that there is a diode D5 (IN4007) which is forward biased when mains is on, and acts as reverse biased when on battery. i guess your diode might be leaky. Please check it using an analog or digital multimeter. And to control the automated illumination use the switch !!!

Regards
Shiharan Choudhury
(RF engineer/ Professional electronic repairer)

• Shreyash says:

Sir,thank you for the circuit.But the problem for me is that when the main supply is off,the led’s still glow with the charging led still on.Help me out sir.I have to show this circuit tomorrow as my project

• Abn says:

hi,
I couldn’t find 2.2K pot.can i bypass/modify it?

• Seetharaman says:

Hi Bashir it looks like your LM317 is a faulty one, replace it with a reputed make from standard supplier. if you feel your present circuit is ok in all respects except the faint glow in charging Diode add a Zener diode of 3.3 volts 1/2 watt in series with the LED which should solve your prolem.

Dear sir when main power supply is OFF, and the circuit is connected to the battery the CHARGING LED still glows. but when i disconnect i the wire that is connected from T2 base to the D1 (of rectifier) the CHARGING LED becomes OFF but as well the main LEDs ARRAY also become OFF. i am using transistor 8550 for T3, also T3 becomes hot. plz help in correcting my mistake, so that CHARGING LED does not glow and LEDs array remains ON when circuit is connected to battery and main power supply is OFF. Please help me sir, my circuit is almost final just facing this problem……..plz help. plz reply……….

dear sir, the ON/OFF switch as shown schematic is creating the problem. when the switch is ON then when main supply if absent and circuit is connected to the battery the CHARGIND LED GLOWS which should not be. But when i OFF the switch then the CHARGING LED does not glow and the circuit operates perfectly. but this switch has be kept ON as whenever main power supply become unavailabe the Lighting LEDs should then go ON. so where i have done mistake that by keeping the ON/OFF switch ON the current flows in such away that the CHARGING LED glows back from the battery even main power supply is off. plz reply in detail…

dear sir, my ZD5 is not getting reverse biased and hence the current flows from the battery, in a result the CHARGING LED (RED) does not go off even in absence of main supply. please help in this regard.

• seetharaman says:

Hi Bashir once the supply is off for glowing the LED should get the supply from the battery, which is not possible as D5 will get reversed biased, hence no current can flow.

dear sir, i am really thankful to you for your kindness, brilliant support and knowledge sharing attitude especially for people like me who are beginner to electronics.
sir, my issue of current flow to the battery has resolved by correcting pin configurations of lm317. but sir if you dont mind, i want to ask one more question. i.e. every thing is working perfectly but sir when main power supply is off, the CHARGING LED INDICATOR still glow, while it should be off as at that time main supply is off. sir, kindly reply why it is behaving like this…thanks once again dear sir for your tremendous support.

• seetharaman says:

Hi Bashir check LM317 for pin connections. This circuit has to work and working. kindly consult any one of your nearby experts for the probable mistakes in your assembly.

dear sir, i have removed T1, and then checked the flow of current to the battery and issuse is still there, the current flowing is still at 1mA. ( i have used correctly 4.7 ohm sir, and have thoroughly checked each and every component as per required specification). sir i have also removed ZD1, but it also did not solve my current issue. i once again installled the component on breadboard, (all new components) but the issue is still there even in the new circuit on breadboard, sir. i am completely confused sir at this stage what to do becasue i have checked all the possibilities………plz sir reply in detail and help me out of this problem…….

• seetharaman says:

Hi Bashir remove T1 and check for the current flow to battery, what is the value you have used for R16 is it 4.7 ohms or 4.7 kilo ohms.

• Manjit Singh says:

Dear Sir,
I have same problem. I drained the battery to 5.8v, But current that flows to battery is 1mA.

sir i have discconnected T1, but the current does not raised to its desired position, also i have changed my transformer from 12v @1A to correct specified one i.e 9v @500mA. but the issue of the low current flow to the battery and voltage drop still remains there. (i have the C6V2 5t written on ZD1..plz check it). Also sir when the main source is disconnected the current and voltage that flows to the load is perfectly all right. but i am amazed that why there is low flow of current to the battery instead the battery is drained properly as you said. sir, i am also doubtfull if the T1, T2, and T3 are soldered other way round, but may be its not true as the current from the battery flows perfectly fine to the load. please explain in detail so that i can overcome the issue…

you mean sir if i disconnect T1, and the current comes back to the desired position, then i should change the ZD1. (my ZD1 is C6V2 5t written on it) or should i change the T1. please explain a little bit more in detail. so that i can act accordingly.
Also sir i am really thanful to quick response and you are really helping alot of people.

• seetharaman says:

Hi Bashir disconnect T1 and try if it becomes alright check ZD1 voltage.

dear sir, i drain the battery from 6.6v to 6.0v for almost 45 mintues more than you said, but the current issues still exisists there and the current that flows to the battery is on 3mA. do you think that its some other problem. i should i drain more the battery say to 5v etc. plz reply…

• Seetharaman says:

Hi Bashir please drain the battery with a load of 1amp for 30mts and try the charging current it will increase. a fullt topped up battery cannot consume any current, hence only a very small tricle current will flow.

dear sir thank alot for reply, yes sir i have installed a good heat sink the voltage has become stable at 6.9v but i am facing current issue i.e the current that flows to the battery is only 1mA and not 450mA as you mentioned. how to resolve the current issue.

• Seetharaman says:

Hi Bashir you have to raise the voltge output to 6.9 to 7 volt. a fully charged battery terminal voltage will raise to 6.9 to 7.2 volts. Check whether the heat sink of LM317 voltage regulator is adequate if not use a good heat sink to reduce its dissipation once the IC getting heated up the output will fall down due to it’s built in thermal protection acting, hence a very good heat sinl for LM317 is a must.

sir i am using 12v@1A transformer, i have assembled the circuit correctly and throughly checked each component. the voltage to the battery is set to 6.4v but there is a current issue. the current that flows to the battery is very limited and its only 3mA and i think the battery requires about 450mA and above. sir why current is so much less, 3mA is no thing for charging 6v 4.5Ah battery, although my battery is brand new. i have also checked it with another battery but the issue remains the same. sir plz reply me where i have done the mistake.

dear sir, i have set the voltage in open circuit without connectiong the battery to 6.9v using 4.7k pot but while monitoring the voltage on digital multimeter, the voltage slowly goes down and reached to about 6.4v to 6.5v. i mean the voltage as you have mentioned should be set to 6.9v which i did, but it is not static and doesnot remain its position but rather it slowly goes down. sir plz reply me what mistake i have done.

Dear sir, i have assembled the circuit and have over come my mistakes, but i am still facing one problem that the charging stops at 6.6v, also when i disconnect the main supply the LEDs comes on automatically but with a little delay, say a second. please comment.

dear sir, i really appreciate your brilliant efforts and your support for the readers, especially for those who are new to electronics as i am. i have assembled the circuit as mentioned but i have some problems.
1) first i have adjusted the pot 4.7k and its perfectly set to 6.9v in an open circuit but when i connect the battery and measure the current then its not 450mA while charging battery, and the current passed is about 19mA approximately. why?
2) i connected a fully charged battery from some other source with the same specification to my circuit and tried to check the volatge at T3 but it is not passing the voltage and shows zero voltage on the meter, why?

• Lan says:

Thanks for your reply Sir. Another questions if you may, What is the purpose of BC548 transistor and how did you compute for the base resistance value 1200 ohms? Suppose I would change it to a different value, will it affect the circuit’s performance?

I’m sorry if I am asking too many questions.

Thank you so much in advance.

• Seetharaman says:

Hi Ansari raise transformer current rating to 2Amps (9Volt 18VA)and replace R16 with 1ohm 5watts and LM317 with LM338. This will take care of your requirement.

• Seetharaman says:

Hi Lan the gain spread for BD140 is given clearely in Philips component data book. Th gain curve with respect to collector currnt is also given, you can interapolate the curve. With the sample used the gain may vary due to the tolerance of the components used. I have given clearly it is the minimum guaranteed gain. in practice it may be more than that, which will not affect the performance of the circuit.

• Dear Mr. Seetharaman:I am a non technical man. Your circuit “Modified Automatic LED Emergency Light using LM317″ is is a very good circuit, I like it, but charging time overnight is much,can you help me, if charging be completed within 5 hours please. email id akansari@gmail.com
I will be very thankful, if replied please.

• Dear Mr. Seetharaman:I am a non technical man. Your circuit “Modified Automatic LED Emergency Light using LM317″ is is a very good circuit, I like it, but charging time overnight is much,can you help me, if charging be completed within 5 hours please.

• Lan says:

Good day Sir!I’m just wondering how did you get the hfe value of 50 @ 500 ma from the BD140 transistor. I have the specification sheet but I can’t figure out how did you come up with the mentioned values. Thanks.

• Lan says:

Good day Mr. Seetharaman. Can you mail me the solution for your computations in the LED Lamp Circuit and Battery Charger Circuit? We made this really nice circuit as our project, and we need to justify every values measured in it. I have done some computations but I came up with different values with the one you did.

I send my warmest gratitude and appreciation in advance for your candid response.

• ram says:

hi sir!i am a second year engineering student.i am gonna do a mini project on the automatic low power emergency light.sir,please tell me the operation of the circuit of automatic low power modified emergency light.i am not getting a clear picture of the working.

• SUVAM says:

Hii SIR, I want to know that in this circuit the led’s will on automatically in the power cut off ? Please please reply sharp.

• Dii says:

Hi Sir! Good day! I have a problem on connecting another bd140.. All leds including the indicator turns on while the power supply is on.

• drix says:

hi sir. am i gonna change any material if i use 5k potentiometer and 230v to 0-9 v 750 ma transformer? thanks. )

• Basit says:

and also a 6.8 volt zener diode can be used or not.

• Basit says:

Sir I want to ask that can I use 9V 250mA transformer because I have one of it and the casing in which I am making this light has also do not have much enough space to adjust a 500mA transformer so what should I do to make the circuit compatible with 250mA transformer.

• eshwar says:

Nice project! what changes needed to be done to this modified version of the emergency light, to control the brightness of the LEDs, to conserve battery power and prolong the duration of the backup.

• Dii says:

• Seetharaman says:

Hi it should be atleast 2 watts.

• Dii says:

Hi Sir, how many watts is that 4.7 ohm resistor?

• seetharaman says:

Hi Naveed the PCB shown in the following project is for fully modified Automatic emergency light you can use the PCBs the layout and components are shown,
http://www.circuitstoday.com/automatic-led-emergency-light#simple

• naveed says:

pcb required of this led emergency automatic schematic updated

• naveed says:

can you send me the pcb of led emergency light schemati

waiting

• seetharaman says:

Hi Gurdeep The LED will glow when ever the battery is getting charged. once battery if fully charged it will go off.

• GURDEEP SINGH says:

when will the led nearer to transistor BC548 will glow.

• Seetharaman says:

Hi Gurdeep thanks for your feedback. this will give a positive approach and confidence for the project builders.

• GURDEEP says:

It is working perfectly.

• Seetharaman says:

Hi Nitin it is for setting the output voltage to 7.0volt by disconnecting the battery, hence the maximum output voltage is limited to safe value.

• nitin says:

one more question, what is working of varible resistance in this ckt?

• nitin says:

ok sir thank u.

• Seetharaman says:

Hi Nitin if you open circuit the zener only the stray and PCB leakages will affect but if it is in circuit it should operate normally. Have you checked R15 value it should be reduced to 330 ohms as I have explained earlier for LEDs to go off when mains is available. Kindly check your assembly step by step, there may be some mistakes, the above circuit is a proven circuit.

• sasi says:

sir,
i need white led based brightest
emergency light use with 12v
7Ah battery and need back up
for minimum 8 hours.which one
is better constant current driver
or pulse boost led driver. please
suggest me some circuits.

• nitin says:

Thanking you.

• nitin says:

so, if this is happening then under voltage protection ckt will not work, because during under voltage zener will not pass any current (open), but due to stray fields(as u said) leds will remain on, so is there any permanent solution?

• Seetharaman says:

Hi Nitin since T2 is a PNP transistor its base bias will from negative that is supplied by T3. (you may call it as return path of bias- T2 emitter base current flows through R17 T3 to negative.
Check by shorting base emitter leads of T3 (by a screwdriver tip)light should go off, indicating no bias is available for T2. By opening Zener ZD2 the base of T3 is floating stray field / print leakage can pass some current to T3 which in turn can bias T2 for glowing LEDs.

• nitin says:

when i remove zener(open ckt), used in under protection ckt, then also leds remains on through battery, why?

• nitin says:

when i remove zener used in under protection ckt, then also leds remains on through battery, why?

• nitin says:

in ckt when transistor T3 is ON, then according to me current through R17 will be flowing away from base of T2 towards the negative terminal of battery through collector of T3, so potential across R17 will be such that it will be positive (bcoz of flow of current from right to left through R17) at base of T2 , so how will T2 (PNP) get turned ON?

• sasi says:

sir,

i need white led based brightest emergency light use with 12v 7Ah battery and need back up for minimum 8 hours.which one is better constant current driver or pulse boost led driver. please suggest me some circuits.

• seetharaman says:

Hi Dap This is due to the gain of transistor BD140 you may reduce the value of R15 to 330 ohms to solve the problem, this I have explained in my earlier comment also.

• Dap says:

Sir, I have tried the modified circuit, my problem is the LEDs turn on while it is connected to mains. What do you think is wrong with the circuit Sir? When I tried to disconnect the bc548, r18 and zd2, it worked.

• Ding says:

Good day Sir! Can you please explain the current flow from input to output in detail? From the transformer to led. Hope you’ll reply. Thanks in advance

• seetharaman says:

Hi Ajitkumar remove T1 and check whether it is raising. if ok then the zener diode is defective. if no check the pot value and R1 value
Hi chandru disconnect the power plug and use the on off switch provided to operate the light as a normal light

• Chandru says:

Sir,i saw your automatic low power emergency light circuit.It is automatically ON and OFF.But i want to ON and OFF it manually. What can i do?

• AJEET KUMAR says:

Hello Sir,
LM317 Output volt (without connect battery)did not increasing maximum 6.6v. i will adjust vr1 4.7k, but volt adjusted maximum is 6.6v only. pls tell me solution of this problem.

• seetharaman says:

The PCB design is available with all modification in the following automatic emergency light simple model project
http://www.circuitstoday.com/automatic-led-emergency-light#simple

• AJEET KUMAR says:

Hi! Sir,
please send me the PCB layout art work for Automatic LED Emergency Light-Modified Version with low battery automatic cut-off system.
Regards.
ajeet kumar

ajeet16@rediffmail.com

• Seetharaman says:

Hi Dojo for a 12 volt battery you require 13.8 volt cycle use, 14.4 volt for storage use and 15.2 volt for boost charging (to activate the battery). For 14.4 volts you can use one 12 volt zener with 3nos 4148 or 1N4007 is series with it to achieve the required protection. with battery disconnected set out put voltage at the wire connecting to battery with VR1 to 13.8 volts. (To achieve this your transformer should be rated for 12volts or higher)

• DOJO says:

Hello sir, thanks for the reply. As I wrote above, I’ve changed the circuit for 12V battery. In this case I think I have to set the pot VR1 for output of 13.5 Volts.
I need the protection part, to keep the battery safe.
These days I was thinking to do another experiment. to use a smaller voltage zener diode connected in series with a bipolar diode, like 11.5 volts (made of two zeners connected in series). Do you think that this may help on the higher tolerance zener diodes?

• seetharaman says:

Hi Dojo disconnect BC148 and set the pot VR1 till you get 7 volts at the battery end without battery connected. now connect the BC148 if the voltage falls down zener is of higher tolerance, if you feel you cannot get a better close tolerance zener delete bc148 portion fully, as this is only an additional protection towards over voltage. if you feel all these adjustments are difficult kindly use our simple emergency lamp circuit
http://www.circuitstoday.com/automatic-led-emergency-light#simple

• DOJO says:

anyone? any idea why this circuit doesn’t work? It’s like the transistor bc548 acts like a resistor connected in parralel with the VR1. How can be fixed?
Thanks

• DoJo says:

Dear Sir, I have the same problem as Rizky has. I’ve adapted this circuit for 12V/7Ah battery and used a 12V Zener for ZD1 and a 5K potentiometer. The problem is that the output voltage to battery is maximum 12.2 Volts, and it is variable only from 1.1 to 12.2 Volts. If I disconnect the zener diode, the battery voltage increases and can be set to around 13.5V (and up to more than 20Volts. I am using a 24Volt/4Amp transformer). What do I do wrong?
Thank you!

• Assem Shawkat says:

Thanks Seetharaman.

• seetharaman says:

Hi Assem it is available in the net in various sites. this site is with all explanations and improvements for the help of hobbyists.

• Assem Shawkat says:

Who designed this circuit ?.

• seetharaman says:

Hi Chetan connect all bases and emitters together keep collectors seperately, connect to individual load line (LED groups of ten or twelve).

• M.P Chetan says:

Sir, how to connect BD 140 transistor, in series or in parallel.

• Rizky says:

I’ve been using 9-volt transformer. but indeed in my town is very difficult to obtain components with a precise value. not only the transformer, but all the available components have a large tolerance value.
maybe I need trial and error until this circuit can work.

Thanks a lot Sir.

• seetharaman says:

Hi Rizky i hope you are using a 9 volt transformer with the rated current capacity, if so no problem should be there. i think you are using a 6volt transformer instead of 9. The input voltage to LM317 will be 12.6 volt the drop across LM317 is 3volt hence you should get 9.6volt. temporarily disconnect ZD1 and battery measure the voltage output to battery with the pot you must be in a position to adjust 7 volt. now just connect the zener diode D1 and check the output voltage (still battery disconnected) if the voltage falls down your 6.2 volt zener is higher tolerance type actual voltage across it may be less than 6 volt. you

• Rizky says:

anyone can help me how to adjust the voltage?

6.9-7volt at pin out lm317 or in terminal to connect to battery?
during adjustment, the 6.9-7 volt achieved with a zener diode connected or disconnected (temporary) from circuit?

thank you…

• seetharaman says:

Hi Chetan you have to use 4 nos BD140, you can use upto 48 LEDs. for 40 you drive 10LEDs with each BD140

• M.P Chetan says:

Sir, what changes I have to make for 40 leds.

• Rizky says:

Dear Sir,

in other post you suggest to temporary disconnect zener and measure the voltage. i follow your suggest then i measured the voltage. at pin out lm317 raise to 8.41 volt, at cathode D5 7.82 volt, at end terminal (open circuit) 7.79 – 7.80 volt.

then i check the zener diode and it is indeed true 6.2 volt zener diode. the installation was correct, the anode is connected to the output leg of R2 (1.2k) and the cathode is connected to the output leg of R16 (4.7/5w).

thank you Sir.

• Rizky says:

Dear Sir,

i am new in electro. i confused how to adjust voltage. where i must check 6,9 volt – 7 volt? at pin out lm317 or at end of terminal (to battery)?

if you mean 6,9 – 7 volt at end terminal (open circuit without battery), would not that would open the zener diode and send bias to t1 then causes the voltage breakdown (t1 thought that the battery is full)?

thank you Sir.

• Rizky says:

Dear Sir,

I assembled your circuit, but i have problem. with 10k pot in highest resistance, the voltage after R16 (4.7 ohm/5watt) only 6.21 – 6.26 volt.
and then i checked other point, output from rectifier diode (D1-D4) 9.5 volts, voltage after c1 and at pin in lm317 9.5volt. voltage at pin out lm317 drop into 6.8 volt, voltage after D5 (Chatode) drop into 6.3 volt, ad then voltage after R16 drop into 6.21 – 6.26 volt.
what wrong with my circuit? thank you for Your help Sir.

Rizky

• Rizky says:

Dear Sir,

i assembled the circuit, but the voltage output for connect to Battery only 6.26 volt.

i use 10k pot vr. the voltage out from D1-D4 9.5 volt, after C1 still 9.5 volt. at lm317 pin out the voltage 6.8 volt. and then after D5 voltage drop to 6.3 volt. after R16 (4.7 ohm/5watt) voltage drop to 6.26.

i try to charge the battery but the voltage of battery only up to 6.41 volt and not raise again.

what wrong with my circuit Sir? thank you for your help Sir.

• seetharaman says:

for36 LEDs of 3volt 25mA you require 3nos BD140 LED drivers with each stage driving 12 LEDS. you require 900mA current say 1amp for 12 hrs use you require a 6 volt 12AH battery. the charger should be capable of 3amps same above circuit with ICLM338 instead of LM317.

• Yogesh says:

Dear Sir,I want to use 36 LED’s working for 12 hours, then what capacity of battery i needed? What kind of changes required in circuit?

• Pete says:

sir, in the first time i run my project it was running normal but yesterday my project got into trouble. how can i fix it? this time even if the lamp is in a source, it still light. what should i do to fix it sir?

• seetharaman says:

Hi Rana why do you want to waste energy, anyway you have to use 5 ohms 2watt or 5 watt.
Hi Pradeep refer to my other simple emergency light project.
Hi Vaibhav SCR cannot be used.

• vaibhav says:

can 1 SCR handle the operation of both t1 & t3

sir,i assembled the circuit and it works very fine. during the day time also if the supply is off, light is switched on. in order to stop this i suggest to connect an ldr. but where to connect it?and another thing is that what is the maximum number of leds can be used in the circuit?

• rana sarwar says:

my dear sir i have 6 volt acid battery and 24 LED in parallel circuit how much resistance value i use in circuit thanks

• Seetharaman says:

Hi Richards you are correct it is EBC. If you are using 4.5AH battery and say your load is 50mA each chain 12chains 600mA. Hence the battery should last for 4500mAH / 600mA roughly 7hrs. To Find out the current use 2nos LEDs inseries apply 6volts DC to it check the current drawn.
http://www.datasheetcatalog.org/datasheet/MicroElectronics/mXvusvr.pdf
Hi Shruti I dont understand your requirement.

• SHRUTI says:

sir, can we modify the above circuit by using atleast 4 transistors.. i need to know it within 2 days .. please help me out…and please mail me the circuit

• richard says:

hey pete maybe you could help me with my questions

• Pete says:

Thank you sir for the help. My project was successful, although i made some few changes it still works. I will share to you my few changes later. Now i have to work for the documentation of my project.
Thanks a lot for you’re help.

• richard says:

i need to show in my paper how to calculate the time that the battery can supply the power for continuous illumination.. i used the 6V 4.5Ah batt. what’s the formula ? thanks

• richard says:

im using 8550 transistor instead of BD140.. the pins are E B C right?

• richard says:

• richard says:

how do i know if the leds im using is rated for 25mA or 50mA??

the indicator still glows even if the battery is not connected. what to do?

how do i use the multimeter to check the charging voltage of potentiometer?

how long does it take to recharge 6v battery?

what’s the max. area achieved by the light?

how long can the battery supply the power for the emergency light?? if you could provide some calculations, please give me .

thank you.

• richard says:

no more fireworks for today im so glad. i connected the wiper to the indicator. the circuit’s already ok. when connected to mains, the battery is charging. when unplugged, the LEDs glow..however, i still have the problems about the LEDs. guess i’ll be workin on it when im not busy again . thanks man

• richard says:

where do i connect the wiper of potentiometer? im redoing the whole circuit again. i realized my mistakes lol

• seetharaman says:

Hi Richard The circuit is correct. Each loop is rated for 6 volt as the LEDs are rated for 3.0 volt at 25mA the excess 3.0 volt is dropped, by 0.6volt at BD140 and balance 2.4 volt is dropped across 100ohms series resistance.

• richard says:

the leds are connected in parallel, and the resistors are in series. is this correct?? thanks.

• seetharaman says:

Hi the pcb shown is for the fully modified mode including low and high cut off. it is not exactly for the simple version, for simple version also it can be used by introducing suitable links.

• josh says:

dear sir,
thank u for earlier reply.. sir , is it possible to assemble modified version of your circuit on simple emergency PCB ? if you have PCB layout for the Modified versions of the circuit ..plz provide to me.. realy i need it.. plz make areply.. waiting for your reply.. joshnair@yahoo.com

• seetharaman says:

Hi Pete it is for limiting maximum charging current. you can use 5 ohms 7 watts. you can use two 10 ohms 3watt in parallel.

• Pete says:

sir,i can’t find exact 4.7 ohms for the r16. r16 is for what sir?

• seetharaman says:

Hi Josh the PCB is available for the fully modified version in Simple version of this LED PCB and Supply PCB
http://www.circuitstoday.com/automatic-led-emergency-light#simple
Hi Aseem ZD1, T1 and R2 required to cut off charging of battery once its terminal voltage reaches 6,9 to 7volts.

• Assem Shawkat says:

Dear Mr. Seetharaman
I need some more detailed information about the function and operation of ZD1, T1 and R2. I appreciate if you send me any documentation you might have to my Email address:
assemshawkat@hotmail.com
Thanks/Regards

• josh says:

dear sir,

i have assembled the ciruit in a general purpose pcb.. its working ..nice..realy ur circuit is usefull..sir, will you plz mail the pcb and its layouts if you have designed it.. i really need it.. hope that u will help me.

joshnair@yahoo.com

• seetharaman says:

Hi Richard to isolate the problem without connecting to mains, link collector and emitter of BD140 if the LEDs are glowing normally, indicates problem around BD140. If the glow is still bad check the battery voltage and the resistance. may be you have to check the LEDs individually. Try the first step you will succeed the collector base emitter pin outs are different for BD140 from the traditional pin outs. watch.

• richard says:

ohhh it’s already workin but the LEDs dont emit uniform lights, and only 6 LEDs are workin..

• richard says:

are the LEDs connected in parallel and the resistors in series? or i have to connect it the other way?

• seetharaman says:

Hi Richard if you donot want it say during day time when you are away you may not need it hence the switch is shown,
Hi Pete you can use 8550 most recent transistor for BD140 for BC148 you can use 2N2221 or 2N2222.

• Pete says:

Mr. Seetharaman,i can’t find BD140 and BC548 what can i substitute for this components?

• Pete says:

Mr. Seetharaman,i can’t find BD140 and BC548 what is the substitute for this components?

• richard says:

do i have to put the on&off switch?? it’s supposed to be automatic right?

• Assem Shawkat says:

Thank you Mr.Seetharaman

• Seetharaman says:

Hi Aseem you require 2.5 mp power pack. ou have to change the transformer to 9volt 3amp capacity. change all 1N4007 rectifiers to 1N5404. change LM317 to LM338 with proper heat sink. other components need not be changed.

• Assem Shawkat says:

Hello Mr. Seetharaman
If I will use a 6V 10Ah battery, what components need to be changed in the circuit?.
Thanks/Regards.
Assem Shawkat.

• vinod says:

Juan, 230V 50Hz is the AC power supply you get from a socket on your switch boards in your house. please take a two pin plug, cut it at one end you have two wires now, connect these two wires to your transformer primary.

• Pete says:

thanks

• juan says:

Seetharaman or anybody out there, i just wonder what do you call that part of “230V 50Hz” ?? i mean what shall i tell the seller if im gonna buy that part? i already have all the parts excet this one .thanks

• juan says:

@pete, 1/2 watt

• Pete says:

another thing sir, the resistors is it 1 watt or half?

• Pete says:

can’t find 6 volt 2-3 watts, only 220 volt 3 watts, is it ok?

• Assem Shawkat says:

Mr. Seetharaman
If I will use a 6V 10Ah battery, what components need to be changed in the circuit?.
Thanks/Regards.
Assem Shawkat.

• seetharaman says:

HiJuan no need to change anyother component.
Hi Pete the PCB is available in
http://www.circuitstoday.com/automatic-led-emergency-light#simple
LM317 has no replacement. if you can get LM7808 fixed 8 volt regulator you can try the above simple proven circuit.

• juan says:

AM i gonna change the materials if i use 5k pot? i’m excited to do this one since we always experience loss of electricity here in philippines.

• Pete says:

sir, what is the other substitute for the LM317? i can’t find one here.

• Pete says:

Sir, can you also please send me the layout of the pcb?
If you could, please email me here. caballarpet@yahoo.com
tnx sir.

• Pete says:

Thanks a lot sir, it really helps.

• seetharaman says:

Yes Pete delete R3 to R14. use one number 6volt 2 to 3 watt bulb.

• Pete says:

i mean, or neglect the r3-r14?

• Pete says:

Sir, if i use 6volt 2 to 3 watts bulb in place of LEDs, do i still need to add r3-r14? on neglect it?

• juan says:

AM i gonna change the materials if i use 5k pot? i’m excited to do this one since we always experience loss of electricity here in philippines.

• maegan says:

thanks so much!!

• seetharaman says:

Hi Maegan that is charge indicator. once the charge is complete the LED will go off. With LED with 2.2K you cannot get open circuit voltage of 6.9 to 7.2 volts (without connecting the battery) hence you have to increase to 4.7K In place of BD140 you can use the recent 8550 PNP planar epitaxial transistor. You can use 5mm high bright white LEDs . Hope this will help.

• maegan says:

(a)in the modified version (not the voltage cut-off protection), the pot to be used is 4.7K or 2.2K??
(b)and also what could be an alternative for BD140?? i can’t find one..
(c)can i use 5mm white LEDs instead of 10mm??
(d)what is the purpose of the LED near the IC and 1K resistor??

thank you! God bless you! im sorry if i have too many questions..

• maegan says:

(a)in the modified version (not the voltage cut-off protection), the pot to be used is 4.7K or 2.2K?? (b)and also what could be an alternative for BD140?? i can’t find one..
(c)can i use 5mm white LEDs instead of 10mm?? (d)what is the purpose of the LED near the IC and 1K resistor??

thank you! God bless you! im sorry if i have too many questions.

• seetharaman says:

Yes Pete you can use 6volt 2 to 3 watts bulb in place of LEDs, BD140 can handle load up to this value. The PCB drawing is available for the modified version itself.
http://www.circuitstoday.com/automatic-led-emergency-light#simple
Hi Maegan it is for rectifying AC voltage to DC voltade.

• Pete says:

sir, can i use a light bulb instead of LED?

• Pete says:

sir, i can’t picture the view of the circuit board, can you please attach some pictures of it? thank you sir.

• maegan says:

Hi may i know what’s the purpose of D1-D4??

• seetharaman says:

Hi Rej it can be done on breadboard.

• rej says:

• rej says:

can this be done in breadboard? i’m really a newbie in doing circuits.

• seetharaman says:

You have to change the transformer with 15 volts 2 amps rating. replace LM317 with 337. replace the voltage set pot to 10k so that the output voltage can raise to 15.2 volts DC on ouput open circuit,

• murali says:

sir i want to replace 6v 4.5ah battery to 12v 7ah please tell me what or d changes required

• Pete says:

Sir,
It helps a lot. Thank you sir.

• seetharaman says:

Hi Pete you can use even a single LED (3.2Volt @ 150 to 300mA) if that illumination is sufficient. The full calculation and explanation is available in the project itself. I have divided the circuit into two parts and given full explanation
1. LED lamp circuit
2. The Battery charger circuit
hope this is sufficient.

• Pete says:

sir,
our group decided to choose this circuit for our project. i want to know if i deduct a resistor or a led in the LED lamp circuit, will it affect the turning on and of the circuit?
i also want to know the full details about this project. if you are willing to help, please email me the whole details.
thank you!

• seetharaman says:

Hi Treena what do you want to convey on this project?

• i’ve had shin splints and once i got brooks they went away. Also i hear that the new rezig’s are helpful with shin splints.

• syed says:

sir,
In my circuit without battery mains on condition all 12led’s glow.If mains off led’s also off.this circuit is correct or wrong? if wrong send me the changes or solution. awaiting yuor reply

• syed says:

sir,
pls send me the operation of this circuit.mail Id:ss_baboo@yahoo.co.in

• syed says:

hello sir
i will try 20k pot also but the volt didnot raise 6.6v across the battry terminal(w/o battery). which place the volt measures? battery connected terminal(w/o battery) or LM317 output terminal 2? pls reply me

• syed says:

Thank yoy sir.

• Assem Shawkat says:

Thank You seetharaman.

• seetharaman says:

Hi Assem adjust the pot on output of 317 on open circuit (battery not connected)it should be around 6.9 to 7 volt. which is the correct requirement.
Hi Syed increase the pot value to 10K and connect 11k or 12 in Parallel with it, this will take care. With mains LEDs will not glow only when supply fails it will glow from battery supply. 12 volt transformer can be used but you have to use a big heat sink for LM317 to keep it cool. The above circuit is automatic once power fails the LEDs will come on automatically.

• Assem Shawkat says:

Hi Seetharaman.
This is my second notice to my question.
I found that the max. voltage I can reach at the output terminal of the LM317 is 7 volts. is this normal??
Regards
Assem

• syed says:

sir,
If main supply 230v failed,led-12nos on automatically. So pls tell me circuit modification.pls mail me my mail ID.

• syed says:

Hello Sir,
battery volt didnot raise 6.9v. i will adjust 4.7k, but volt adjusted maximum is 6.6v o
nly.pls tell me solution of this problem

• syed says:

sir, i have only 12v transformer and without battery. how can i test the circuit, if without battery circuit work or not (LED glow or not).Pls reply me

• Assem Shawkat says:

Hi Seetharaman.
This is a notice for my previous question.

Please Notice that I did build the lower part of the circuit, the battery charger only. I left the LEDs and the T2 control transistor for a later stage.

Assem

• Assem Shawkat says:

Hi Seetharaman.
Thank you for this circuit. After building the circuit and at no load (battery or LEDs) to what voltage should we adjust the output terminal of the LM317 using VR1?
Thanks/Regards.
Assem

• ajith says:

i’m doing my engineering in mechanical…….. i’m doing one project….. in that i need a circuit to detect the oxygen level… which should be cost effictive. please sent that

• seetharaman says:

Hi Sankar this circuit is suited for LAG cells. not for nicad cells, as the requirement is constant current of 1/10 rating. you have to modify this circuit totally. you may have to look for our future projects on nicad rechargeable emergency lights. LAG batteries are cheaper, hence they are preferred for the projects than nicads, which are quite expensive.

• S. Sankar says:

January 10, 2011 at 5:40 am
Can the latest circuit of yours be used for 5 nos. 1.2 volts 2000 mAs. (in series this works out to 6 volts) Ni. Cadmium batteries. Can I give parellel connection (2 sets of the cells) so that the ampere is high?

Please respond to this mail that I posted on Jan. 10th. My email id is: yesemve@yahoo.com or yesemve@gmail.com

• seetharaman says:

Hi Murali use just 4 LEDs instead of 12. Reduce R3 to R6 to 22 ohms.

• murali says:

dear sir
iam having 8mm 0.5watt 100ma leds can i use in this circuit or any change is requir and how many leds should i connect.

• Seetharaman says:

Hi Srinivas PCBs are available in the other project use them.
http://www.circuitstoday.com/automatic-led-emergency-light#simple
For every 12 LEDs add one BD140 or the recent 8550.

• Srinivas D says:

Dear Seetharaman,

Please send the PCB lay out of above circuit to my email id dsrini73@yahoo.com.

Secondly, I want to connect 40 LEDs to this circuit, please suggest suitable transistor.

Next, wanted to incorporate low battery indicator and please suggest where to connect the LED and resistor value.

• Sankar says:

Dear Mr. Seetharaman,

From your reply i hope that you are in Chennai. If you don’t have any objection, please give me your address.I wish to meet you personally, for some of my projects. You can send it to my e-mail id: yesemve@gmail.com / yesemve@yahoo.com.

Thank you,

Sankar.

• aswin says:

thank you boss for your kind reply. But ples help me with that automatic night light also.. Thanx to mr.Harry also

• Seetharaman says:

Hi Jhantu the same circuit will do no need for any change. Hi Aswin you can use SS8550. which is freely available.
http://www.datasheetcatalog.org/datasheet/MicroElectronics/mXvusvr.pdf

• Harry says:

ASWIN, in which country you live ? Website’s like digikey, mouser and farnell have options to search based on parameters.

• aswin says:

hi
i would like to assemble this circuit., but for my unluck BD140 is not avail for me. ,i tried for 2N2905 also,but no hope. So ples help me, smbdy tell me sme transistors that can be replaced in place of BD140.ples help me. I also added a comment in the topic ”automatic night light with timer”, i will be greatfull to you if u help me.. Plezzz…..

Thank you

• Jhantu says:

Sir,
If I use 6Volt 5.5Ah Battery charging circuit are same??
How many watt use for resistors??

• Seetharaman says:

Please go to simple emergency lamp circuit that is the artwork of the PCB used for these projects.
http://www.circuitstoday.com/automatic-led-emergency-light#simple

• SA says:

Sir,

Please send me the art work for PCB layout for Automatic LED Emergency Light-Modified Version.

SA ( goodguyid@mailcity.com )

• abhishek D says:

sir and other guys ,those of you who have completed this circuit, pls send me a diagram showing the naming of terminals of the bd140 and bc548 transistors…
here is my mail:
abhi.dav@gmail.com

• Ahmed says:

Hallo,
Seetharaman, hope you are fine.

First of all i would like to appriciate you for the work that you have done and for the support that you are providing to the readers individually. This is really really a good and a positive activity.

I build this circuit about a month back. There are no issues. Worked so fine, I’m just willing to share my experience with other readers.
Guys, I Could not get a transformer with 0-9v output at 500mA but got at 800mA, which is Working fine. No issues at all.
Please be careful in identifying the pin connections of the bd140 and bc548. This is critical for the correct working of the circuit.
I used an on/off slide switch in series with battery that i found was added by the author in modified version. A good addition in deed. I used a RED LED to indicate the charging the battry. Any value is suitable but it should be 2.7k Min. 6.8k Max.

The beauty and the simplicity of this circuit is really somthing to admire.

Thanks alot seetharaman.
May you be happy always.

• Seetharaman says:

Hi My PCB art work is available in http://www.circuitstoday.com/automatic-led-emergency-light
Hi Robin for your requirement my above link with MOSFET IRF540 switching will be suitable.
Hi Chrystopher You can use emitter resistance/pot to take care of brightness.

• Christopher says:

Hi Seetharaman

I want to dim the LED’s for interest sake. How do i connect a Pot in the circuit. DO i have to connect it to the base of transistor? Maybe a 1k pot could be used?

• Rizwan says:

Hello Seetharaman please send me the art work for PCB layout for Automatic LED Emergency Light-Modified Version.
Rizwan ( ali_ahmed_rizwan@yahoo.com )

• Rizwan says:

Hi! Sir,
please send me the PCB layout art work for Automatic LED Emergency Light-Modified Version.
Regards.
Rizwan.

ali_ahmed_rizwan@yahoo.com

• SOUGATA says:

Hi Seetaraman,

i want to make this project, but with 80 pc leds and 6v, 5.5Ah sealed lead acid battery.
And can i replace BD140 to a higher rating transistor for increasing the no of leds.
so tell me the modification can i do or you can mail me with modification details with ckt dgm.

E-MAIL ID:- sougata.kundu51@gmail.com

• robin says:

Dear Sir,
Please help me for selecting an appropriate battery in SIZE….6volt 4.5Ah is used in our old emergency kight naa? With me a 36 LED platform, but the casing is small…. please tell me the SMALL SIZE battery with this value or please tell me if there is any choice of two 3 volt battery combination with current value….

• Seetharaman says:

Hi Roshan check the zener disconnect and try as i have indicated in my previous reply. now check both the circuits-LED glow circuit and charger circuit separately as indicated in the article. With mains if LEDs are glowing reduce R15 to 390 ohms.

• Roshan says:

When i re soldered some connections, this is what happens:- i changed
it to 10k potentiometer…but,still the charging voltage is below 6v…All
the LEDS in the LED section glows when charging. When I disconnect the
main supply, the leds in the LED section glows, but, it is very dim.

when i connected the charging leads to the battery, and then connect
it to the indicator LED, the indicator glows, and the LED section
turns off. Otherwise, the leds in the LED section glows(which shows
error).

Why is this?

• Seetharaman says:

Kindly check up your Zener diode ZD1. disconnect the diode one end and try adjusting the pot for 7.0volt now connect ZD1 if the voltage falls ZD1 is not rated for 5.1volt. measure the voltage across ZD1 if it is less replace with the correct one. You contact Mr. Ravi 9841394518 for your requirement of PCBs and LEDs.

• Roshan says:

Where can I buy, the pcb of the modified emergency lights using led?

• Roshan says:

Hello sir,
i changed it to 10k potentiometer…but,still the charging voltage is below 6v…All the LEDS in the LED section glows when charging. when i connected the charging leads to the battery, and then connect it to the indicator LED, the indicator glows, and the LED section turns off.
Why is this?

• Roshan says:

Thank you Seetharaman…But, even if the charging voltage is low, the led should have to glow theorethically. but, it is not glowing.

similarly, the battery, when connected directly to the leds, they glow, but, in the circuit, it is not glowing. why

• Seetharaman says:

• Roshan says:

• Seetharaman says:

increase it to 10k

• Roshan says:

I tried to increase the charging voltage by turning the pot, but, the maximum it increases is 4.69 volts…..an i forgot to mention, the preset pot i am using is 4K7

• Seetharaman says:

Hi Roshan LA batteries require constant voltage for charging . for cycle use 6.9 volt is the limit recommended by battery manufacturers. hence without connecting battery you have to set the pot for 7volt if not getting increased change the pot to 10K. The LED will glow while charging, once battery is fully charged it will extinguish.

• Roshan says:

Hello Seetharaman,as in your comment dated june 17,2010,related to a query about adjusting the pot, you said that we have to adjust the charging voltage to 6.9-7 volt. Is it that, only a charging voltage of 6.9v can charge the battery. The voltage at the wires that is to be connected to my battery is less than 4 volt. Do I need to increase this? Do i have to turn the pot to increase this voltage. I have a preset potentiometer. Please reply.

• Roshan says:

Hello Seetharaman…I have dropped the work in making the basic automatic emergency light circuit, and have started the modifies automatic emergency light with under voltage cutoff protection.

It is seen that there is a small led connected to the 4.7K preset variable resistor. What is the use of it? Does it glow when connected to the mains?

After assembling the entire circuit, nothing happens. Neither the LED section glows, nor the small led near the variable resistor glow.

How to know whether the circuit is working properly?

• Seetharaman says:

Hi Crystopher This transformer is best suited you can use. 0.5 watt is ok, use 5% tolerance zener diodes., pcb details are available in my new emergency light project use it.

• Seetharaman says:

Hi Crystopher This transformer is best suited you can use. 0.5 watt is ok, use 5% tolerance zener diodes., pcb detaols are available in my new emergency light project use it.

• Christopher says:

I found a transformer thats 230vac-9vac and 670mA, is it fine or do I have to make changes?

• Roshan says:

Can you send me the pcb design of the modified version of the circuit to my email. My email is roshanvallappillil@gmail.com
Thanks

• Christopher says:

Hi Admin, could I use 0.5W resistors for the above circuit? And the zener used should be atleast 5% tolerance or less?
Which is prefered?

• Roshan says:

What LEDs should I use, i.e, whether I should use 5 mm or 10mm leds?

@ Roshan
I used 5mm LEDs. Size doesn’t matter but you have to consider the current/ voltage ratings.

• Seetharaman says:

Hi Christopher kindly send ma an email i will send the pcb design
seetharaman

• Christopher says:

Hi again sir,could you also send a PCB layout of the final modified circuit via email thanks

• Christopher says:

Hi there sir,could you please add some calculations on how i obtain the correct size heatsink as i really want to use this for my project at school and if you could reply soonest it would be much appreciated

• Seetharaman says:

Hi CW one BD140 can drive 12 LEDs of 25mA each. You add more BD140 in parallel and connect 12 LEDs for each BD140. Since the battery used is 4.5AH, for 5 hrs use you can use 3 BD140s and 36LEDs.

• CW says:

How many LED max can be added for this modified circuit?
Rgds

• BHAVESH says:

Dear Sir,

I have mailed you my address on “seethasub@hotmail.com” please send me the art work of the Automatic LED Emergency Light-Modified Version.

Many thanks.
Bhavesh.

• Seetharaman says:

• Bhavesh says:

Hi! Seetharaman,

How are you sir, can you please tell me if the PCB layout for this Automatic LED Emergency Light-Modified Version is ready, if yes then where can I see it.

Regards.
Bhavesh.

• Seetharaman says:

Hi Figo your suggestion 1 is fine saving component and reliable but it will not take care of deep discharge circuit with T3. T3 circuit can be improved similar to our voltage sensitive relay by including a potentiometer so the required cut off voltage can be set (due to spread in voltage of zener diode – tolerance of the diode)
http://www.circuitstoday.com/three-phase-auto-changer-circuit

• Seetharaman says:

Hi Hotshot it is a good idea, there is an efficient version is under design in that we will try to incorporate your suggestion.

• Hotshot says:

In fact the emergency lighting should has an opto sensor circuit add in as power failure during day time with the emergency light turning on is just a waste. Battery will not last till night falls. Hope this can take into consideration. Thank you.

• Figo Chen - Shenzhen China says:

Im glad seen so many reader send their comments on this circuit to make the circuit has been more perfects, but I still has some comments:

1. Regarding the Transformer:
The linear transformer is not good to to provide the stable voltage, when the input voltage drop to 180Vac in some conditions, then the tansformer output voltage will be reduced too, that will cause the LED light up @ 180VAC input.

Suggestion:
A: Connect base of T2 directly to output of LM317.
B: Delete R17 AND r15, change discharger circuit, see below.

2. For over discharger protection circuit:
In current discharge protection circuit, the battery will not stop even the T3 is turns off, becoz the base of T2 alway stay at about -1.4V when AC input is cutoff.

Suggestion:
1. use a voltage comparator IC such as LM358 to do voltage detection on battery for overdischarge protection.
or who can provide a simply circuit to us will be better.

• андрей says:

Dear SHEETHARAMAN. Designed the lighting for your new circuit with a device from a deep discharge battery. Unfortunately just a device I have does not work. The rest of the scheme is quite rabotosposobna.Skazhite please, if you have solid evidence of efficiency is the device from a deep level in this scheme? Have you ever been repeated єtu scheme. I’m interested in is protecting against deep discharge batteries. If you can, marking the transistor BC548 from right to left on the conclusions. (In the datasheet information about labeling this transistor is different) Thanks.

• chennareddy says:

hi sir.
presently am using 12volts 7ah battery for my system UPS, i want to change that to 12volts 40ah. will the ups work properly or is der any problem by doing such changes…

thanks……

• John says:

sorry, I mean 12v 60Ah

• John says:

Hi! Seetharaman,
Thank you for sharing!!
I want to make this project, but with 100 led and 12v 7Ah lead acid battery, could you please mail me the circuit

Thanks & Regards
John

• min says:

dear sir, can u pls mail me about the first circuit on THIS page/link. i have to write a report on this circuit. sir if you cud please help me write the abstract it would be greatly appreciated. i dont know what is hapenning in this circuit.sir pls tell me how exactly this circuit works. can i use a 300mA step down transformer instead of a 500mA one? also is BC140 transistor equivalent to BD 140? sir do pls mail me your reply.thank you

• JUBIN says:

• Krishna says:

Hi Seetharaman, I have 12 v lead acid Battery and I would like to setup led light circuit.Kindly publish the circuit which can use 12 V battery as power source.

• Sankar says:

Can the latest circuit of yours be used for 5 nos. 1.2 volts 2000 mAs. (in series this works out to 6 volts) Ni. Cadmium batteries. Can I give parellel connection (2 sets of the cells) so that the ampere is high?

• Bhavesh says:

Hi! Sir,

How are you, can you please tell me if the PCB layout is ready for Automatic LED Emergency Light-Modified Version, if yes then where can I see it.

Regards.
Bhavesh.

• priyanka says:

Sir,
How can i modify this circuit by connecting a batterry level indicator?.Please repley.

• Seetharaman says:

Hi Amdani T1 will take care of that function automatically when the terminal voltage falls below the set voltage.

• Amdani Wijaya says:

Hi! Seetharaman,
Thank you for sharing!!
Is this circuit can begin charging automatically when battery is weak?

Thanks & Regards
amdani

• Seetharaman says:

Hi Mint you are correct, it is not that it cannot be charged during day time. normally during 10pm to 6am wthese are not used hence it is normally said that it can be charged over night.

• Mint says:

Thanks for the circuit. You mentioned that the battery can be fully charged at night, then someone would use the light in the daytime? Rather it should charge in the day and and show light in the night. Anyway sometimes we also need light even in the day. Thanks again.

• Bhavesh says:

Hi! Seetharaman,

How are you Sir, can you please tell me if the PCB layout is ready for Automatic LED Emergency Light-Modified Version, if yes then where can I see it.

Regards.
Bhavesh.

• partha sathua says:

i want to know the full description of circuit operation of the above circuit

• Seetharaman says:

Hi Adnan your charger capacity is 5amps. your battery is 50AH(not only amps but also the current for how many hours). your charging current is 5amps hence it will take 10 hours to charge the battery. capacity of battery / charging current (50 / 5)

Suppose if we have a battery charger which is giving 12v @ 5A and a car battery of 50A?
what time will the battery take for full charge?plz tell me the calculation also??

Suppose if we have a battery charger which is giving 12v @ 5A and a car battery of 50A?
what time will the battery take for full charge?

• Seetharaman says:

Hi Bhavesh this pot should be adjusted in such a way that the battery charging current is limitted to 1/10 of the battery capacity. in this case 450mA. If you cannot achieve it, reduce R16 to 2.2 ohms and adjust the pot for 450mA charging current (when the battery terminal voltage is around 6.0 volts). This will charge the battery over night to its rated capacity.

• Bhavesh says:

Dear Mr. Seetharaman,

Thank you very much for your previous reply, Please tell me if the VR1 setting is kept for full, max voltage, will the charging stop at 6.9 & start charging at 5.2 volt of the battery??? As I am keeping the VR1 on full for faster charging, as my circuit is charging only at about 250~300mA. with a transformer of 9V 500mA. Regards. Bhavesh.

• Abhishek says:

5. Ic is 1.25 / 180 = 7mA
6. Ibe = Ic / hfe of T1 i.e = 7 / 70 = 100uA
7. Drop across R2 =1.2 X .1 mA = 0.12volt

why ic is 1.25(volt)/180(ohm)???

• Seetharaman says:

Hi Sindhu kindly tell me which is the costiest part in your place i will suggest alternate.

• Sindhu says:

Sir!!
Can any other alternative components can be replaced to reduce the cost of the circuit???PLzz sujjest me sir………

hi if we use 3volts using a resistor from 6v 4.5ah battery then will it gives 9amperes @ 3v?

• Seetharaman says:

Hi Bhavesh If you have a constant current source with a burden of say 30 volts you can use it. if not use a 30volt power pack use a 4.7 to 5.6 K resistance in series and feed it to zener diode. if you are getting say 0.7 volt across the diode you have reverse the leads. The drop across the diode is the voltage of the zener diode. choose the correcrf value zener and use it.

• Bhavesh says:

Hi! Seetharaman, can you please tell me in details, how to give 5mA curent to check the zener??? Thank you for your earlier reply. Best Regards.

• Seetharaman says:

Hi Murali you have to check the pot value increase it to 10K and try the voltage if it is not increasing to 10 volt your IC 317 is faulty or wrongly wired.
reduce 560 ohms to 330 ohms or so it should solve your problem.(it can be any value between 220 to 330 ohms.

• murali says:

hi sir d open circuit voltage at positive lead to battery is 5.7volts and R 15 i used 560 ohms

if we use 3v using a resistor from 6v 4.5ah battery then will it gives 9amperes @ 3v?

• Seetharaman says:

Hi Gururaj please wait i will make a prototype test and comback to you soon.

• C.S.Gururaj says:

Hi SeethaRaman,

Can you please publish this circuit with a 12V 7AH battery. I tried the same with modification suggested by you earlier. But it is not working as expected. BD140 is not turning off LED’s when mains supply is available.

Regards,
Gururaj

• Seetharaman says:

Hi Murali what is the open circuit voltage at positive lead to battery with pot VR1 is at maximum resistance value. what is the resistance value you are using for R15.
Hi Adnan you can use the same circuit add 1no BD140 parallel to existing BD140. connect base to gether, connect collector together use 0.47 ohms with each transistor emitter and then connect it to battery positive through light on / off switch.

i have a pcb of an old emergency light having 60 leds coonected in parrallel what transistor will i use to make automatic switching system like above light????

• murali says:

sir iam not able to increase d battery voltsmore than 5.6 volts
when power resume d led is not switching off it glows dim pls send me reply

regards

• Seetharaman says:

Hi Sindhu I am enclosing my earlier reply to Mr. Kumar on
June 10, 2010 at 9:09 am
Hi Kumar the PCB is getting ready will all improvements. once it is ready, will inform.
For enclosure you can use any one of the old 2 tube enclosure with single 6volt 4AH battery. The appoximate cost with High Bright white 12 LEDs, new battery PCB will be around (you can use the transformer available in the old light) INR 500 to 600

• Sindhu says:

Hi Sir!!
Can U tell me D approximate cost of this circuit ??????

• murali says:

sir iam not able to increase d battery volts more than 5.6 volts.
2. when power resumes it is not switching off d led glows dim

• Seetharaman says:

Hi Bhavesh check zener diodes ZD1 & ZD2 for their correct voltage by feeding 5mA constant current through them. If they are different from the indicated value their tolerance are quite high try to use 5% or better. It has to stop charging at 6.9 volt plus minus tolerance of the diode. similarly switch off glowing LEDs at 5.7 volts.

• Bhavesh says:

Hi! Seetharaman, I have assembled this circuit on a bread board, but it does not disconnect the battery at 5.1 Volts, also it does stop charging at 6.9 volts. Please sir tell me what I have to check, or change. Regards. Bhavesh.

• Rajesh Kumar Joshi says:

Hi,

I tried this circuit with 30 LED’s and it is working fine.
Can we also have a full charge indicator (LED) in this circuit.

Also, I am looking for a 12v lead acid automatic battery charger.It will be great if you can help me with your expertise.

Thanks
Rajesh

• seetharaman says:

Hi Ifan you see mains operated LED it is 230 volt 25LEDs
“Mains Operated LED Circuit”. It is tested and proven circuit.

• ifan angelo says:

sir, please send me the schematic for 24 led.
i want only 220 V AC to 24 led.

thanks and regards
ifan angelo

• ravi says:

Thankyou sir

• seetharaman says:

Hi Ravi the pot is required to set the max current for a flat battery.
try by reducing R15 to any value between 220 and 330 ohms it should solve your problem.

• seetharaman says:

Hi Boo the pot is required to set the max charging current for a flat battery.(approx 1.2amps)

• seetharaman says:

Hi Adnan you can rectify fix limitting resistance or surge protective device and use it.
LEDs can work only on DC. If you use AC you have to take care of reverse voltage protection during negative half cycle.

will this leds works on A.C volts?

can i drive 80leds in series with 220volts?

• Sindhu says:

Thanqq for U’r reply sir !!!

• ravi says:

Sir the led section working very well but when power resumes the ckt not switching off and glowing dim,please suggest solution for me

• ravi says:

Sir in this ckt can give a fixed resistor value to the adjust pin lm317

• seetharaman says:

Hi Sindhu you use the normally closed contact of the remote control relay to suplly power to the emergency light once the supply is disconnected, the LEDs will come on automatically once the remote connects the power LEDs will go off and start charging the battery.
The PCB is getting ready with alternate like 12volt 36LEds or 24 LEDs 6 volt 12 LEDs it will be ready soon i will send the lay out and the template soon
hi mounica it requires lots of modification it is now available in my new pcb please wait.

• mounica says:

dear seetharaman

how can i use this circuit for 12v 7Ah battery

• Bhavesh says:

Hi! seetharaman,

Can you give me the PCB layout of this circuit for 6V & 12V battery charging, with your new modified circuit. I will be very much thankful for the same. I tried it out on the bread board but could not get the required mA, I am getting only 45 to 50 mA, with 9V, 500 mA transformer. Rest all my circuit is working ok, my email add bslpei@dataone.in
Regards.

• Sindhu says:

Thanqq for U’r answer sir !! But know i am in a conffusion that where i have to attach this receiver ckt in this emergency light .Can U help me sir???

• seetharaman says:

Hi Sindhu you can use the ultrasonic remote control appeared in these columns for your remote operation of LED lights
the article appeared as “Ulhttp://www.circuitstoday.com/ultrasonic-switchtrasonic switch”

• Sindhu says:

Sir !
Can i operate a remote controll for operating these LED’s.I did found any remote controll for operating LED’s in any website .Can U plz help me in doing this ???????plzz reply me….and also for my mail……

• Sindhu says:

Sir,
I sended U a mail to seethasub@hotmail.com please reply for that sir….

• Bhavesh says:

Hi! seetharaman,

Can you give me the PCB layout of this circuit for 6V & 12V battery charging, with your new modified circuit. I will be very much thankful for the same. I tried it out on the bread board but could not get the required mA, I am getting only 45 to 50 mA, with 9V, 500 mA transformer. Rest all my circuit is working ok.
Regards.

• Boo says:

Sir Seetharaman,

wat purpose of VR1 4.7K on the circuit.should it be always set at max?

• Gururaj says:

Hi SeethaRaman,

Can you please publish this circuit with a 12V 7AH battery. I tried the same with modification suggested by you earlier. But it is not working as expected. BD140 is not turning off LED’s when mains supply is available.

Regards,
Gururaj

• seetharaman says:

Hi Adnan it will become 12Volt 4.5 amp battery. batteries inseries will add up voltage. batteries in parellel will get their current added.

if connect two 6v 4.5amp batteries in series will it becomes the 12v 9amp battery or the 12v 4.5amp?

• jun canas says:

make one that will run on 12v and with car battery, please,
4f5tac,tacloban, philippines.

• seetharaman says:

Hi Adnan you are correct it will become 6volt @ 9 amps battery.

if i use two 6volts @4.5amp batteries in parallel will it become a 6v @ 9amp battery?

• SINDHU says:

Thanqq for U’r kindly reply sir !!!!

• seetharaman says:

Hi Sindhu add one more BD140. that is connect both the bases together similarly connect both emitters together and to the collector of added BD 140′s connect the next 12 LEDs as per existing circuit. my email is seethasub@hotmail.com

• emmi says:

• SINDHU says:

And also can i use 9V battery ?????

• SINDHU says:

Sir,
U said that the base and emitter terminals of BD140 should be shorted.R they can B shorted by connecting them to the existing switch in the above ckt???Is the 1st LED of next set can B connected(in ||el)to D 12th LED in the previous set??Sir can U give me U’r ID so that i can mail U the expected ckt 4 D 24 LED’s (OR) U only mail me the ckt 4 24LED’s.Plzzz sir reply me……

• seetharaman says:

Hi Sindhu add one more BD140 connect base and emitter torether. in its collector connect 12 LEDs as per existing circuit. now you can have 24 leds. fix heat sink for LM317 and BD 140s they should have electrical isolation to heat sink with insulated mounting kits.

• SINDHU says:

Sir,
Here U used 12 LED’s if i want to use another set of 12LED’s i.e total 24LED’s .Then 4 than what modification should i have to do in the circuit????Where should i have to connect the heat sink for the circuit modified by U(As shown above)????PLzz reply me sir….

what is the mcd of the 10mm led used in this model? what angle is needed to get good lighting? where can i ge 50mA 10mm buton leds?

• seetharaman says:

Hi Magnet the bias for the BD140 transistor is given through this transistor and zener, if voltage falls below the set level the zener will not conduct hence no bias for BD140 hence the LEDs will go off.
Dear deepak you have to use one more BD140, emitter connected to existing BD140 and base to existing BD140 and collector to one more set of 12 LEDs. with 24 LEDs of 25mAs consumption each a total of 600mA is required a fully charged 4.5 AH battery will give illumination for 4.5 / 0.6 = 7 hours appoximately.

• seetharaman says:

Hi Patrick Vaz you have to use a good heat sink for regulator IC LM317 as it has to dissipate around 3 watts.

• Patrick Vaz says:

I Have a 0-12V transormer 500ma and the battery is 6v 4ah will any modification be required in the circuit, Pls respond.

• Patrick Vaz says:

I Have a 0-12V transormer 500ma and the battery is 6v 4ah will any modification be required in the circuit, pls reply.

• patrick vaz says:

Hi,
I Have a 0-12V transormer 500ma and the battery is 6v 4ah will any modification be required in the circuit, pls reply.

• anil says:

Hi,

this is nice job doing every on ,it is now very important requirement in Karnataka ,

• Magnet Electronics says:

Sir,
Very nice circuit.Does the “under voltage cut-off protection section” really switches-off LEDs???!!!!

• deepak says:

Sir,i want to make this circuit with 24 led’s. please tell me what modifications are required for making this? tell me all changed resistors values. and also tell that,with lead acdid battery of 6v 4.5AH,how many hours it will give light? plz reply soon.

• sunnyimran says:

Please mention that is there any kind of current limiting /current regulation also present in this circuit
other than the limiting resistors R3 to R14. ?

is there any role of T2 or T3 in likiting LEDs current?

thanks

• patrick vaz says:

Dear Gentlemen,
A different topic didnt know where to address.
I have couple of 500G hardisk, over the years, have collected movies,i want to play them directly to a TV or LCD, any circuit ideas, which can convert and play movies, directly on LCD,

sir,
please tell watts of all resistors,

sir is any resistor and driving transistor should be added? what about the cost of these leds?

• seetharaman says:

Hi Pradeep you can use 4LEDs in series in each loop. so 3 loops are sufficient. if you use high bright white button LEDs of 3volt 50mA current, 3 loops 150mA hence your batterywill give power to LEDs for minimum 20hrs.
the charging circuit has to be modified fully. please refer to lion battery manufacturers recommondation.

is reflector is needed for the leds? what type of reflectors can be used ? where can i get it?

hai sir,
thank you for your valuable info in this site . in the above circuit if i use 14.4 v,3.5Ah lithium ion battery what are all things i have to change in the above circuit? how many leds can it drive for long time?

• seetharaman says:

Hi Pradeep with 12nos 25mA LEDs it will work for min 12hrs non stop.

how many hours it will work when it is fully charged

• santhosh says:

sir, please send me the 12v 3 or 5amp regulated power supply circuit for audio system if you have any.

thanks and regards
santhosh

• seetharaman says:

Hi Adnan you cannot compare a battery with an amplifier both are of different charecterestics. both the principles are different.

if i give the more current to an amplifier it will draw only the required current but why the battery don’t do that???why the battery not draw only the required charging current?????????

• seetharaman says:

Hi Biman the circuit can be modified add a resistance of required value (r= 0.65 / currnt in amps – please donot exceed 1amp with this IC) between emitter of T1 and battery negative. disconnect R2 from ZD1 and connect it to battery negative. with this modification it will become a constant current charger.

If the supply current is high amplifiers and others devices consumes there required current but why the battery doesn’t do this if the current is high

• Biman says:

Hi seetharaman, Thanks
My problem is solved.
But the battery cherger circuit here is a constant volt
cgerger, I want a constant current cherger for the same

If the supply current is high amplifiers and others devices consumes there required current but why the battery doesn’t do this if the current is high????

if the supply current is high amplifiers and others devices consumes there required current but why the battery doesn’t do this if the currewnt is high????

• seetharaman says:

ZD2 is giving bias to bd140 through T3. if the battery voltage is low BD140 will not get the bias and the leds will not glow

but whats the relation of zener diode with bd140 ??

• seetharaman says:

Hi Adnan for 4volt battery the cutoff voltage at full charge is 4.6 volts hence you require a 3.9 volts zener. and bd 140 to cut off the voltage is 3.5 volt hence the zener should be 2.7 volts.
if you are using anyother circuit kindly send me that i will suggest you.

no i have a fixed charger not the above one and i have a light having 4 volts battery and i want to add a switching system in that with 5v charger light not the above one

• seetharaman says:

Hi Adnan BD140 is for switching on th LEDs. if you want to cut off the LEDs at say 4.2 volt then use a 3.3 volt zener for ZD2

can i charge a 4.2volts 0.7Ah battery with 5volts 0.3A chager??

can i cutoff the bd140 with 5v??

• seetharaman says:

Hi Adnan use 4.2 volts Zener for ZD1

i want to cutoff the transistor with 5v what transistor will i use to cutoff at 5v????

• seetharaman says:

Hi Biman try by reducing R15 to 270 to 330 ohms. this should sole your problem

• Biman says:

Hi Seetharaman,
I have made the circuit but not working.
then I understand that biasing of BD140 is missing from the Battery. please Suggest me the Biasing.

As per your circuit it is lighting when AC Power is ON.

• seetharaman says:

Hi Ankit if you use 12 leds of 25mA total current will be 300mA A ‘D’ size cell with 500mA hr rating will give illumination for an hour and half. (90mts)

• ankit says:

hello sir,suppose 4(1.5v *4=6v)non rechargeable battery is connected with 12led(25ma),then according to calculation for how much continuous hour will it switch on the led? thanx

• seetharaman says:

Hi Arun connct an electronic bleeper between battery positive and collector of Q1 through a 1N4007 diode(cathode toward positive of the battery), once the battery is fully charged Q1 will be turned on in turn the bleeper also will be on

• Arun says:

Hi..It would be helpful if you post a modified circuit for knowing the full charge of battery..

• seetharaman says:

Hi Xplod the battery charger circuit requires to be changed to constant current charger instead of constant voltage charger(suitable for lead acid battery only). the lighting circuit does not require any modification

• XPLOD says:

Hello sir, can i use the circuit with 6V/7Ah NiCd battery since its shown 6V 4,5Ah on the circuit? If not what modifications should be done?

• seetharaman says:

Hi Gururaj You can use 12 volt zener with one 1N4001 in series it will be 12+0.65 + 12.65 volts.
1.8 K is correct.

• C.S.Gururaj says:

Hello Sir,

The Battery’s fully charged voltage is 13.5. So Can I use 13V zener with R2=1K? Calculation will be,

Ib = Ic/hfe = 0.1
Let R2 = 1K
Vdrop accros R = 0.1V
Voltage across the chain ZD1, R2 and T1 be should be 13.5

ZD1 = 13.5-(0.7+0.1) = 12.7 or 13 (Only 13V zener is available in market).

Also, according to calculation I had changed the baising resistor of BD140 to 1.8K instead of 560E. Is that ok or BD140 will never turn off?

Regards,

Gururaj

• Seetharaman says:

Hi Gururaj
R2 has to be 1K only it is there to protect the transistor hence reduce it to 1K.
With 12 volt zener and 1K resistance charging will cut of at
12.8 volt itself.
Similarly LED cut off voltage will 10.8 volt with 10Volt Zener and R18 1K.

After the above modification give a feedback.

• C.S.Gururaj says:

Hello Sir,

I have modified the circuit to work with 12V, 7AH or 12V, 40AH car battery. But the circuit is not working as expected.

The problem I am facing is that :

1) The BD140 is not switching off even when the battery voltage drops to 11.8V.
2) The charging is not stopping even at when battery voltage reaches 13.5V.

Following are my modifications. Please verify the same and let me know what is my mistake.

Fully Charged Bat 13.5
Bat Drain Voltage 11.8
Supply Voltage from transformer : 24V
After Capacitor : 24*1.414 = 33.9V
After drop across 317,D5 and R16 : 33.9-3.7 = 30.2

1/10 of rated charging for
7Ah = 0.7
40Ah = 4.0

R16 value for 7AH = (30.2-11.8)/0.7 = 13E @ 5W
R16 value for 40AH = (30.2-11.8)/4 = 27E @ 5W

BD140
———– mA/Ω A/KΩ

Bais Voltage 0.77
Ic = 300mA 300(for 12 LED of 25mA each)
hef at 500mA 50
Ib = Ic/hfe 6 0.006
Bais Resistance (Ω) 2121 2.121
Bais Res, Bat Drain (Ω) 1838 1.8 (Currently Used)

T1 : BC148
————
Bais Voltage 0.7
Ic = 1.25V / 180E 7
hef of BC 148 70
Ib = Ic/hfe 0.1
Let R2 be 10K
Vdrop accros R = R*Ib 1V

Voltage across the chain ZD1, R2 and T1 be should be 13.5
i.e : 0.7 + Z + Rdrop = 13.5
ZD1 = 13.5 – (0.7+1)
ZD1 = 11.8V or (12V)

Similarly
ZD2 = 10V
R18 = 10K

Regards,
Gururaj

• Seetharaman,V.S says:

Dear Mouly
It is called SPST switch (single pole single throw switch)
In fact you can use any domestic electrical on / off switch.

• mouly says:

Very useful circuit Sir.What is that ON/OFF switch name in the market .Does it have any specification.Is that manual switch or automatic.Please reply me

• seetharaman says:

Hi Satu if you use a narrow beam LEDs you will have problem. I have used high bright white LEDs of 25mA rating. They are giving goor illumination similar to 7 watt emergency lamp, ofcourse not all around only 180 deg around 90deg brighter illumination. if you have narrow beam leds give an ofset between LEDs say around 15deg. This will help you to spread the light.

• Satu says:

Hello Sir, the second plan is a theoretically complete power cut off emergency led lighting. But led lights are light ray! While you tested it, did the led light spread throughout the room?

• seetharaman says:

Hi Kumar You dont require BD140. It is only required when you want LEDs to come on automatically during power failure. If you want it as an LED torch light/ lantern you can connect (if it is white hi bright) white LED through a resistance to battery. say the LED is rated for 50mA. then 6.9 – 3.2 / 0.05 is the resistance value. you can use 68 ohms in series with each LED. Any number of LEDs with 68 ohms in series with each LED can be connected in parellel. 12 is sufficient if you want an illumaination similar to 11 watts U type energy saver lamp, you use 24 LEDs.

• kumar says:

hello sir, thanx 4 ur response.due to unavailable of some components in the market, i want to divide the whole ckt into 2 parts i.e charging and led ckt.for charging i want to use a ckt of an old emergency lamp which charges 6v/4.5ah lead acid battery.and 4 the led ckt i want to use ur above mentioned ckt.i mean after charging i will disconnect battery from the ckt.it wont b automatic.so what changes i have to made in led ckt.?where the base of bd 140 will b connected.?is it possible to make such separate led ckt with or without using bd 140?

• seetharaman says:

Hi Kumar you can use 3 sets of 12LEDs with BD140 each with three switches.
Normally LED will go open circuit hence no problem, it will not affect.
For LM317 a cooling clip is a must, even it is 12 LEDs.

• kumar says:

hello sir, …1)suppose i connect 3 sets of 12 led with bd140 each.and 3 switches for the 3 set of leds,so as i can switch on any or all of them.is it possible? if 1 led blows then will it affect the others??
2) whether heatsink will be required for lm 317??

• seetharaman says:

Hi Sanju without connecting battery measure the charging voltage and set it for 6.9 to 7 volt. After this adjustment connect the battery.

• Sanju says:

Dear Sir;

What is the procedure to adjust the pot.Kindly let me the same.Regards;/Sanjeev

• seetharaman says:

Hi Aji 2200uF can be used. Kindly assemble as per the above values indicated in the modified circuit.

• Aji says:

hi guys,,i tried to make this circuit.But there are many problems with my circuit.I have got 2200uF capacitor instead of 1000uF.Resistor with 16ohm resistance is not available to me…Is there any problems with these.Whether this problems affect my circuit

• kumar says:

hiii seetharaman, thanx 4 the reply..plz let me know whenever pcb with improvement is ready.i really need it..thanx.

• Sk A. says:

Dear Mr.Seetharaman,
I had gone through this.Thanks a lot. We want one Emergency Light manufacturing unit. Now small way. Can you pls help us giving the Kits/Boards.. We want LED Emergency Light or CFL Emergency Light to be run by Rechargable Sealed battery of 4.5 AmP or more or less which can give a three hours backup.. Pls mail my Email id..Waiting for your reply,Best.

• seetharaman says:

Hi Adnan For 12 LEDs one BD140

how can i use two bd14o how aill i connect them i want to increase 38 more leds
so how much bd140 i will use?

• seetharaman says:

Hi Adnan the reply i have given on this on May 16th

May 16, 2010 at 12:47 amHi Faraz Khan You can use 3 circuits of 12 leds driven by its own BD140. That is connect all the three BD140 emitters together. base through 680 ohms from each BD140 base to -ve rail. 12 Leds as above to each BD140 collector. this will enable all the three BD140 to share the current equally.

but you say use two bd140 how will i connect the two bd14o

yes i already using the big heat sink when the 36 led is lighting the bd140 is get hot

• seetharaman says:

Hi Kumar the PCB is getting ready will all improvements. once it is ready, will inform.
For enclosure you can use any one of the old 2 tube enclosure with single 6volt 4AH battery. The appoximate cost with High Bright white 12 LEDs, new battery PCB will be around (you can use the transformer available in the old light) INR 500 to 600

• seetharaman says:

Hi Adnan 36 X 25mA 900mA a lot of current you require a very good heat sink for cooling BD140. I want the current to be distributed such that a small cooling clip will do.

but sir my light is working on 36 leds on one bd140?
what is the drawback of one bd140 on 36 leds?

• seetharaman says:

Hi Yofan yes you have to change the transformer also to 15volts secondary.
Hi Prasanth you have to use 2 more BD140 circuits so that you can light upto 36 LEDs. Say each LED consumes 25mA then you require 900mA, Battery will last for 4hrs before requireing to recharge

• Prashanth says:

Dear Seetharaman,

Is it possible to connect 30 LED’s to the above circuit?

• yofan says:

Hi Sir,
it’s possible modified your charger from 6 volt batt to 12 volt batt with only replace the zener diode ?
and also it’s fully automatic batt charger right ?

• kumar says:

hello SEETHARAMAN,thanx a lot 4 the modified ckt..i want to work on the above ckt..so to mount the above ckt, whether general pcb r availaible in the mkt or else what i have to do??hope u undrstand..question is regarding pcb.and what will be the approx cost for making this ckt in rs..thanx..

• seetharaman says:

Hi Sankar with a small modification, change of transformer and 3 LEDs in series we can have a circuit with improved efficiency. I will try to send one soon.

• Sankar says:

At times of rainy season, current available time is less. So I want a modified circuit diagram of 12 volts. With less number of LEDs i can use the charger for a long time.

• Sankar says:

Thanks a lot for this diagram. Can the same circuit be modified for a 12 volt battery circuit with different charging levels?

thanks

• seetharaman says:

Hi Adnan I will mail you soon

plz give me the quick charger circuit for this light or tell me how to increase the current for quick charging?
or mail me the circuit i shall be very thankful to you

ok then upload a charger circiut plz

• seetharaman says:

Hi Adnan you have to make a different charger circuit of the required capacity. Existing design is not meant for it.

i have 4.5amp battery and the 30% of 4.5 is 1.35amp tell me that or modify the circuit that the existing power supply will give approx 1.2 or 1.3 amp?thanks

• Arun says:

Sorry..i thought that 548 is pnp…

• Arun says:

hi..all..i hope the transistor shown is BC547 instead of BC548…

• seetharaman says:

Hiu Adnan you can fast charge the Lead acid gel cells with 30% of the rated current, say in 3 1/2 hours you can charge fully. Ensure the battery is not getting heated up warming up is normal.

i want to charge the battery quickly tell me what will i do because it takes a long period for charhing so how i can charge the battery quickly?

• seetharaman says:

Hi Adnan Normally these small trasformers will have no load current of 8 to 10mA @ 230 Volt. So 2.3 watts of energy is always consumed even without load. These trasformers normally has a loss of around 15% at rated load. 9 X 0.5A that is 4.5 watts as the efficiency is 85% the primary requirement will be 4.5 / 0.85 = 5.3 watts. 5.3 + 2.3 = 7.6 watts will be the primary power requirement. All these calculations depends on the quality of the transformer. price is proportional to quality.

how much power is consumed by the 9v 500mA transformer tell me the formula that i will able to calculate the watts consumed by transformer so i will calculate the electric bill?and also tell me the electric bill calculating formula Thanks

• seetharaman says:

Hi Adnan this was my earlier rely to one of our constructor

May 15, 2010 at 8:51 am
Hi Faraz Khan use an electronic sounder (phezo electric) in parallel with diode D5, +ve of the sounder to cathode and -ve to anode of D5. When the battery is getting charged the sounder supply is reversed (you get around -0.7volt). once the battery is fully charged T1 switches on the battery will supply sounder around 4 volt for it to sound. If dont want negative voltage of 0.7 across the sounder add a diode inseries with the sounder to block negative voltage.

i hav e succesfully use this circuit but i want a modification when the battery is full charged an led indicator will glow so we can get n switch the power off so upload a circuit diagram with this modification i shall be very thankful

• seetharaman says:

Hi Prasanth, mail you mail ID to seethasub@hotmail.com i will send you the modified circuit with your requirement. i have already posted the modification required to ADMN, “circuitstoday”

• Prashanth says:

Hi seetharaman,Thanks for the reply.Can you please elaborate & send us the modified schematic.

• seetharaman says:

Hi Prasanth you can use a BC148 with a 5.1 volt zener similar to charge limitting circuit and its collector to be connected to the 560 ohms available at base of BD140 instead or returning it to common negative. When the battery terminal voltage falls below 5.7 volts the LEDs will be switched off.
Hi Adnan As per the battery manufacturer’s recomondation maximum charge current cannot exceed 1.2 amps. and charging voltage canot be more that 6.9 volt for cycle use. Hence a 6.9 volt regulator with maximum current limit set at 1.2amp is a must. If these precautions are not taken, the life of the battery will get dramaticaly reduced. For cycle use over night charging(8 to 10 hr charge cycle) is strongly recommended. Each LED drawing 20 to 25mA 36 LEDs will consume 0.9 Amp Hr. The recommended batery can give an useful glow of 3 to 4 hrs per charge. If you want more duration you may have increase battery AH capacity and the charging circuit accordingly.

hi I’ve successfully made this circuit with 36 leds and my light is working and it give 6hour(not continuous)
but if i use 24 volts(12-12) transformer instead of 9volts can i replace the transformer and if i do this will the battery charged quickly?

• Prashanth says:

hello sir.how can i implement the under voltage cutoff for the
LED Emergency Light Circuit,since battery get drained.

• seetharaman says:

Hi Tutul you can try 5volt instrument cooling fans, which are avilable for low price or you can get one from a old defective power pack. ( used for PC power supply cooling).

• TUTUL says:

it’s nice. but it’s need’s a LVD circuit.

• seetharaman says:

Hi Digaonto you can use a standard 6volt DC fan with 9″ blade Connect -ve to battery negative and +ve through a switch to battery positive. These fans work normally for 3 hours with fully charged battery. The fan consumes around 1.25 amps.
For operation during power as well emergency use, increase transformer rating to 2amps all rectifiers to 3amps ( eg. 1N5404) use the standard current increasing technique for LM317 with a PNP power transistor like 2N2955 and a resistance of 6.8 ohms. with this your fan can operate always. during emergency will operate for 3 hours.

• Digonto says:

Hello Seetharaman,
There is no doubt that it is really an excellent & efficient circuit for those countries like us where Load-shading is daily routine . I also want to add a motor to make fan in this circuit . Which volt’s motor will I use ? Will I use 6V or 9V motor ? And the motor will run also while the battery is charging too .

So, From where and how will I connect the motor line . The motor will run in both time- while the battery is charging & in emergency(from battery) time . – Thanks

• seetharaman says:

Hi Michael if PMPO is your requirement as per your link then you can construct 60 watt RMS amplifier, in bridged configuration it will give you 240watts RMS. As per your link’s Sony’s specification it will be 5200 watts PMPO. You can use Sub woofer amplifier appeared earlier in ‘Circuits Today’ with modification and covert it to a full range amplifier, bridge and use it.
You require 4 amplifiers to make a stereo system with the similar power supply with the current rating increased suitably.

• michael says:

Dear Sir,i need the circuit diagram of a 5000W audio power amplifier using STK… IC families and another one using transistors.

• seetharaman says:

Hi Saad A fully charged battery can work in this circuit for 12 hours minimum for continuous illumination. 5.6volt is the end point voltage for lead acid gel cells. Hence you have to recharge the battery at this point. This is only a general guide line for a new battery. As the battery ages the characteristic will change.
The LEDs will not glow during charging since R15 gives positive voltage to base of T2 it will cut off the current flow during charging. Once the power goes off the positive voltage goes and T2 gets forward biased and starts conduction to illuminate the LEDs. If there is still very illumination from the LED R15 can be reduced to 100 ohms. This problem I faced with amber LEDs.

• KAMESHc says:

Dear Sir,

It is very nice to view lot of electronic circuit which are useful to many students to learn the technology.

It is to request you to send Synchro to Digital conversion circuit at the earliest.

Thanks

Kamesh

hello sir.how can i calculate the remaining time of the battery?will the circuit glow while batery is charging?

• seetharaman says:

Hi a small correction is left out, the potentiometer to be changed to 4.7K or add 1K in series with the existing pot 2.2K. With 2.2K you will achieve only a maximum of 5 volt.

• sison.c.s says:

sir,
first time i appreciate ur great effort for design such wonderful circuit.since last two years its works well in my home in absenCe of me..let me ask some quisten sir.1-i would like to use power led of 1w-24NOS nos.what modification require?2-please let me know the maximum current can taken from bd140 transistor?3-if i increase transistor means parellel more BD140?4 -can i replace bd140 with 1061 or MJE 3055 transistor?AND WHAT MODIFICATION REQUIRE COLLECTOR EMITTER TERMINAL JUST REVERSE?EXPECTING UR EXPRESS RESPONSE.
C.S.SISON
ALWAHDA MALL
ABUDHABI
UAE-
PHONE HOME-9747447168

• Shiharan says:

Well to get 7v from 9V dc using lm317,simply replace the pot with a 820 Ohm resistor and you will get 6.985 v dc.

• hariesh says:

dear sir,

i made this circuit. i have an issue output of battery charging point (without battery and zener disconnected) shows only 6.4 maximum after preset is adjusted full level volt i cant raise to 6.9 volt.when battery and zener connects it shows 5.12.battery not charging. please can you help me. what could be the issue.?