Sensitive Intruder Alarm Circuit
Intruder Alarm Circuit
Description
Here is the circuit diagram of an ultra sensitive intruder alarm. The shadow of an intruder passing few meters nearby the circuit is enough to trigger the alarm.
Here IC2 uA 741 is wired as a sensitive comparator ,whose set point is set by R6 &R7. The voltage divide by LDR and R9 is given at non inverting pin of IC2. At standby mode these two voltages are set equal by adjusting R9. Now the output (pin6) of comparator will be high.Transistor Q1 will be off. The voltage at trigger pin of IC1 will be positive and there will be no alarm. When there is an intruder near the LDR the shadow causes its resistance to increase. Now the voltages at the inputs of comparator will be different and the out put of IC2 will be low. This makes Q1 on. This makes a negative going pulse to trigger the IC1 which is wired as a monostable multivibrator.The out put of IC1 will be amplified by Q2 (SL 100) to produce alarm.
Intruder Alarm Circuit Diagram with Parts List
Intruder Alarm Circuit Diagram
Notes
- To setup the alarm ,power up the circuit and adjust R9 so that LED D1 goes off.
- The LDR can be housed in a dark tube to increase sensitivity.
- The sensitivity is very important here. If you cannot adjust the required sensitivity properly, use one LOW resistance (~1K ) POT in series with R9 for fine adjustment.
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Thank You.
Hi Ashnuka you can use any low power general purpose pnp transistor
What are the replacements for BC157 other than mentioned below?I’ve searching it and it’s equivalents but no luck.Can i use any pnp?
i want video for making sensitive intruder alarm
please…Seetharaman, i need to know how to get the intruder alarm circuit block diagram and its discriptions…please help me sir.
Hi Seetharaman,thanks for your help.But i found ua741 and SL100 in here.Thank You again.
Hi Ashnuka 741 is a standard opamp and it is freely available. you can use TL071 also. for SL100, you can use 2N1711, 2N2219, 8050, BD137, CL100, BEL100N etc.
what are the equalant components for ua741 and SL100?
. .i’m an EcE student here I got my best project here in circuits today .. .and my professor are so happy that I have my project . remember the transistor based intercom . ..very simple but it was so great ..thank you
. .hi i’m me . .can you help me find what to replace sL100 and bc157 . . out of the market again …. can you give at least 10 replacement to each transistor …I don’t have much money to spent searching the net . .I’l come back tomorrow . .its about our project please help me. .i’m out ..I will be so thank full if i can find answers tomorrow,,
hi seetharaman! I just wanna ask something. I’ve tried you circuit but i have a big problem, cause when I connect the power supply to the circuit, the alarm was already triggered and the the potentiometer really does not vary the sensitivity of the LED… please help me to trouble shoot my circuit.. THANK YOU!
hi guys, what if i want to add-on a timer that act as switch to automatically ON the circuit when we needed? what should we put in there and how? hope u guys can help me.. tnx
hello seetharaman thanks 4 helping me.. i make this circuit and it works..tnx 4 the help..^^..take care alwys
Hi Popsy please go ahead using them.
helo mr. seetharaman..i’ll follow your suggest to me..thank you very much for helping me…^^
ah ok..tnx seetharaman..so its ok that I replace the MPS2222A to the SL 100 and also the Mps4126 to BC 157?? tc alwys MR. seetharaman..tnx^^
Hi Popsy SK100 is a medium power PNP transistor in T05 casing. BC 157 plastic low power PNP transistor and not an equivalent for SK100 2N2905 is OK.
helo Mr. Seetharaman,sir i dont get it..the Sk100?or did you mean the BC 157? thx^^
Hi Popsy MPS2222A can be used for SL100. MPS4126 can be used for SK100 provided the operating voltage is less than 20Volts.
seetheraman can i also replace the Mps2222A in SL 100 and the MPS4126 in SL100??they are general purpose right?tnx^^
tnx seetharaman
Hi Popsy you can use 2N1711 for SL100 and 2N2905 for BC157
hey guys,is there a replacement or a equivalent in the 2 transistors,the BC157 and SL 100..can you help me guys..tnx
whats the value of Q1?
Hi Batutuy The circuit is correct. When the light falls on the LDR it resistance will be low, hence IC output at Pin no6 will go high. Q1 emitter will go high LED will be in off ststus. When the shadow falls on LDR, its resistance will go high and Q1 will conduct and LED will glow with a negative going pulse to IC1 to produce alarm.
HEY GUYS I HOPE THIS CIRCUIT WOULDNT TRIGGER AT NIGHT?
the I think that the LDR and R9 must be at the inverting pin because the non inverting pin is fixed
wat is this k1 written below d buzzer n if i go to the shop to buy the buzzer ,what should i ask for?
circuit is here
we want diagrams
we are technical student please we want the real diagram of an amplifier we will be glad if our request is granted thanks
Great idea!
The only thing I’d be concerned about with a super sensitive alarm is it false triggering all of the time. When used in the right application, its a great circuit.