High & Low voltage cut-off with delay& alarm
Description.
This straight forward circuit will protect electrical appliances from over voltage as well as under voltage. The circuit also produces an alarm when the power supply comes back. An ideal circuit for home to protect your valuable equipments from voltage fluctuations. The same circuit with some modifications can be used to make a automatic voltage stabilizer.
When the mains voltage is in the normal level, the voltage at the negative terminal of zener diode D4 will be less than 5.6 Volts. At this condition transistor T1 will not conduct. The same time voltage at the negative terminal of zener diode D5 will be greater than 5.6 and so the transistor T2 will be conducting. The relay will be activated and the green LED will be glowing.
When the mains voltage is higher than the set limit the transistor T1 becomes conducting since the voltage at the negative terminal of D4 is greater than 5.6 V. At the same time transistor T2 will be non conducting which results in the deactivation of relay to cut the mains supply from load. When the mains voltage is less than the set limit transistors T1 & T2 becomes non conducting making the relay to de-activate and cut the load from mains.
The timer NE555 is wired as a monostable multivibrator with a pulse width of 10ms.When the power comes back after a cut off a negative voltage is obtained at the trigger pin which triggers the IC NE555. The transistor T3 gets forward biased and it drives the buzzer to produce a beep as an indication of power resumption. Also the transistor T1 is made on which in turn makes T2 off. As a result the relay will remain de- activate for 10ms and this provides the sufficient delay and the equipment is protected from surge voltages.
Circuit diagram with Parts list.Click to enlarge.
Notes.
- To calibrate the circuit a autotransformer is needed. Connect the output of autotransformer to the transformer primary.
- Set the voltage to 260V and adjust VR1 to make the relay deactivated.
- Now set the autotransformer to 160V and adjust VR2 so that the relay is de-energized.
- VR3 can be used to vary the volume of buzzer.
You may also like:
please, what will i use to set the cut-off voltage since i cant get the autotransformer. And also please what is the power capacity of the circuit? can it be used to power an air conditioner or refrigerator? please i need your reply, thanks and God bless
Hi Victor for setting an auto transformer is a must.
can you please send me a working schematic diagram?
what circuit can play the same role as the autotransformer,since I could not find it?
can i replace the transformers with the dc supply for 15 v??
Hi Inten the transformer in the input mains supply sensor for the load, hence it cannot be avoided.
I will be very thankful to u if u reply me fast, please.
Hi Madhuri when the input voltage is just above minimum value (say 160volts set by VR3) T2 picks up and relay RL1 switches on to give supply to load. If the load increases more than the safe limit (say 260 volts set by VR1)T1 picks up and removes the bias to T2 such that they RL1 switches off cutting off supply to load. once input voltage falls within 190 to 250 volts range the relay RL1 picks up and the supply to load is restored. The timer is to produce beep once the supply is resumed as well to delay the supply to load such that the inlet surge at the time of power resuming is also not sent to the load.
please give me detailed explination of every component used in this project. please reply me soon
sir,
we select this topic as our project.I Want to know more about the outputs of this.so pleae send me the details of the project as soon as possible
Thanking you.
Hi,
i have read out your query.
send me the parts/component list to me.
iwill giving you the details of those.
list send to stalukdar84@gmail.com.
Hi Madhuri there was an error in my earlier reply on voltage level this is correct one. when the input voltage is just above minimum value (say 160volts set by VR3) T2 picks up and relay RL1 switches on to give supply to load. If the load increases more than the safe limit (say 260 volts set by VR1)T1 picks up and removes the bias to T2 such that they RL1 switches off cutting off supply to load. once input voltage falls within 160 to 260 volts range the relay RL1 picks up and the supply to load is restored. The timer is to produce beep once the supply is resumed as well to delay the supply to load such that the inlet surge at the time of power resuming is also not sent to the load.
can you plese sent me the design?and all abt the circuit diagram.is it working?
Pls sir i was given a project to desigh an construct a high an low voltage cut off wit delay an alarm an i dont know how 2go about it pls can u be of help
you are doing a very nice job, i want you to please tell me where my loads are to be connected . and i need more details on how every component works. thanks very much. my email is popcorn_xin822@hotmail.com. Hope you reply me a.s.a.p
plzz tell me the high-low voltage cutoff with delay and alarm with some modification and advancement in circuit diagram.
plzzzzz tell me the size of the auto transformer to be used, and i didnt get what is no n where exactly the appliance to be checked should be kept ,kind request to you to send me all the details of working of the ckt by tonite
HELLO SIR , I HAVE A QUESTION.. CAN I UPGRADE THE TRANSFORMER TO 1A THEN CAN I WILL ADD 4 RELAYS ON IT??
Very nice post my brother but where will the load be connected,and what is the function of auto transformer here….
From the circuit where do i connect the appliance to be protected for both over/undervoltage conditions.And apart from the auto transformer what else can we use to vary the voltage to the circuit.Also after cutoff how can the appliance be automatically connected to the mains when the fault has been cleared.
Hi Balu VR2 is wrongly shown as VR3 in the schematic. For appliance connection please refer to my 6th Feb comment.
can you plz send me the modified circuit diagram
what is the function of diode in above circuit
please help me to find where vr2 is.Also where should we connect the appliance to be protected in case of over voltage?
how can we connect appliance operating on 230v to a transformer operating at 12-0-12v secondary? & where to connect the load? please reply….
Hi John use the normaly open contact(when the relay is in off condition)of the relay RL1 to switch on off the load.
Hi ipoy20 this is a working model and a proven design for step voltage regulators.
is this working? please send a reply asap. godbless
hey,pliz email me on how to connect the load.
Hi John You can use 2N2219, 2N2218, 8050, 2N1711. any medium power switching transistor can be used.
hey ,thanx for the contribution to technology,i have tried making this project but the sl100 transister is rare so i tried the D313 as an option its still not workin ,pliz suggest another option,thanx in advance.
John.
Great and simple circuit, but I searched for circuit that protects the drive three phase 380V AC interruption of one of the stages, but I did not find it, or the opposite one of them.
Can we use transistors instead of integrated circuit IC 555, for the alarm?
PLS,I WANT FULL WRIT UP ON HIGH AND LOW VOLTAGE CUTOFF PROTECTOR
I vary d vR1&VR2 but d relay keps suplyin when d voltag is high&low.d crct jst wok lik a stab in dlay.pls hlp
Hello, since i’m working on a circuit for shutting off my diving light when my battery’s get too low, i’d like to integrate this circuit into it. However is it possible to leave everything right of Transistor T2 out of it? And could you please tell me if i could directly use this transistor in series with the base of a BUZ11 MOS-FET, wich I am now using to switch my load. Thanks in advance.
Hi Hiren Use standard straight or dotted PCB and wireup yourself. For testing you require a variable auto transformer of 0 to 270volt.
Use the supply to the load to be protected through RLA1 contact
PLZ HOW CAN MAKE THIS ? REPLY PLZ………
Hi, pls i need details of how the transistors and the Zener diodes work. Pls kindly see me through in my email. Thanks
Hi Adamu The load should be connected through the potential free contacts of the Relay RLA1 (NO contact- Normally open contact). The relay will switch off/on the load.
U have done a good job. Pls, where do i connect d load n how does d circuit work, detail pls. Give me d write up. My email is isahadamu25@yahoo.com. Thanks.
i am still awaiting your response in my email, i need you to see me through this. i need details on how the circuit works since i have found this project very interesting and finally approved my supervisor. thanks very much
Hi Rilwan the NO contact of the ralay RL1 is used for controlling the load. I will be in touch with you soon through your email id
you are doing a very nice job, i want you to please tell me where my loads are to be connected. and i need more details on how every component works. thanks very much. my email is rillex55million@yahoo.com
SL100 can be substituted with 2N2218, 2N2219 or 2N1711 switching transistors reliably. If you are in India then you can use BEL100N, CL100 also. The above circuit is very reliable one. I have used it in auto phase change over circuit in house. i will be sending the circuit to “Circuits today” soon.
i need someone who has experimented with substitute for sl100 transistor to give me his/her sub.thanks
Hi everybody,I want to know the tripping circuit for high voltage tester circuit.
Plz i want to build this project, with tyhe circuit diagram of automatic voltage stabilizer and the works pls send me the details to my email address.which is snowboy3k@yahoo.co.uk. thanks.
Plz i want to build this project, with tyhe circuit diagram of automatic voltage stabilizer and the works pls send me the details to my email address.which is snowboy3k0@yahoo.co.uk. thanks.
Am working on one of your circuit(street light) as a project.I need your help on written area(materials).Thanks
where is vr-2, and the 555′s delay should be 10 seconds, not 10 milliSeconds!
How can we make an automatic voltage stabilizer out of it ?
hai sir iam a final year EEE student.i want to do a project on high voltage and low voltage cutoff with time delay(a model based on the circuit).you please give me the information regarding to the operation,you please send the information to my mail.
Thanks for this good cct.
it’s good for our inst. that work in bad local Elec. Voltage
can u please tell me or mail me the circuit diagram of the stabilizer at saqi240@hotmail.com
Mohamed Anany
I am pretty confident that D4 and D5 should be 400 milli Watts and not 400 Watts. 400mW is suggested as it is a commonly manufactured value and therefore normally cheaper.
that was an error in the circuit diagram
D4 and D5 are 400 milli watts. I have corrected the circuit diagram.
Have a look.
thanks to Mohammed and twits4twats for pointing out.
Hello,
Well thank you alot for your response, and i have another question, can i use a lower power diod than the (400w 5.6v D4 & D5 & D10)?, if you have an answer please post it or send me an email, again thank you for your fast response.
best regards
Mohamed
Hello,
First it is a good circuit, but i want to ask about a replacement for the (SL100) transistor, because i have searched alot for that transistor but i didn’t find it. Please if you have an answer for this send me an email.
Thanks
best regards
Mohamed
you can try BD 139, BC 107 or simply any medium power npn transistor
Hello,
I found your circuit simple and interesting.
could you suggest the necessary change I need to do if I want to protect a 6V, 4.5 AH Lead Acid battery from overcharging and over discharging.
To get a steady charging voltage of 7.3V for charging the battery, I will be using a 12V, 500 milliAmp Adapter, Send it through IC 7808 followed by diode 1N7004 in series. That will give me 7.3V.
Thereafter I need a overcharge protection circuit.
Similarly I need to protect the battery from over discharging.
only 30% discharging will be good for me. it will give me a good life.
will you be able to guide me.
thanks
kind regards
shubhro