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    Imagine the Panic situation in the Midnight when an intruder tries to break into the house. This Alarm will help you with its loud Police siren to abort the attempt of intrusion. With a single clap, the circuit generates the alarm for three minutes and then goes off. This is sufficient to catch the attention of neighbours.

    The circuit is a sensitive Clap switch with timer action. IC1 is designed as a sensitive inverting amplifier to amplify the sound signals from the condenser mic. Variable resistor VR1 set the sensitivity of mic and resistor R1 and VR2 set the gain of the amplifier. If the sensitivity of mic and amplifier is suitably adjusted, the circuit can detect the sound from a distance of 5meters or more.

    Panic Alarm Circuit Diagram

    panic alarm circuit schematic

    When the mic detects clap sound, the ac signals pass through C1and IC1 amplifies the signal. This triggers T1 .When T1 conducts, the trigger pin of the Monostable Timer IC2 will be grounded and the timer triggers. With the given values of R5 and C2, output of IC2 remains high for three minutes. This high output provides power to the ROM IC UM3561. It generates the Police Siren since its pin6 remains unconnected. Resistor R8 determines the frequency of oscillation of IC3.The siren signals are amplified by T2 and the alarm tone can be heard through the speaker. Zener diode ZD gives 3.1 volt regulated supply to IC3.

    attentionThe author D Mohankumar is not an active member anymore. Please take into consideration that the presented information might not be correct.
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    56 Responses to "Panic Alarm Circuit"

    1. I just can’t tell u how much I have enjoyed this site !! Though I haven’t recieved any anserws to my questions,,,,yet. I have really looked forward to opening my e-mail to find NEW and different circuits to build and experiment with. I know zealch about electronics but find it alluring and fascinating. I have learned,,,even @ 54 yrs of age and I LIKE IT!!

    2. Dear sir, i want to use panic alarm for my project. But, here are so hard to find ic um3561 and T2 AC187. what the other component that can be replaced for both component? please reply this comment. thank

    3. We cannot substitute UM 3561. It is the siren generator IC.A simple buzzer can be connected at the output of IC555 is UM 3561 is not available. AC 187 can be substituted with BC547/548 eventhough the sound output will be low.You can use a high gain NPN transistor for it

    4. Thank for the information sir.Now, i can proceed my project.

    5. Dear sir, in my easy pc for panic alarm project, there have no pin ic for um3561, so that i have to use ic ne555. but,i dont know which pin to connect. can sir please tell me the pin need to be connected using ic ne555 by refer the ic um3561? thank you,sir

    6. You cannot substitute UM 3561 with 555 IC.Is it a simulation or real building

      • Dear sir,in my pcb board or real building i use ic um3561, but in the software of easy pc i am use the pin of ic ne555 because there have no ic um3561 in the software. i use ic ne555 because just want to connect the pin of the ic.

    7. Sir, i have problem for the circuit of panic alarm. the speaker has sound but not the alarm sound. when i take the reading,all the reading show low voltage..microphone also didnt activated the speaker and zener diode just give 0.55v only even the ic um3561 need 3.1v to be activated.i dont know what the problem. can sir send me a pcb sketching or other that are useful to make the panic alarm function?…thank for your kindness..

      • D.Mohankumar says: on October 17, 2010 at 6:11 pm

        check the output from IC 555. It should be around 10 volts.Red LED will blink when MIC works. Adjust VR1 for sensitivity.Remove 0.22 capacitor and check whether IC1 is working. or not.If it is OK, replace a good quality Mic.

    8. Sir, in the panic alarm circuit, should i add one connection on the pin 5 of ic um3561 to the positive line or just follow the actual circuit shown?

    9. Dear sir, i have testing my pcb for panic alarm circuit. Here, i am using the 3.3v led and when i on the power supply the led reading is 0.6v, the voltage of the microphone is 2.65v..is that the circuit function if the microphone show the voltage 2.65v? thank for the feedback from sir.

    10. dear sir,wrong info from me…actually not 3.3v led but the zener diode which is 3.3v..

    11. dear sir, my panic alarm in the pcb, when i on the mic the will led on, then the led off when i off the micro..but, still not give alarm sound to the speaker but just normal speaker sound out.. the vr1 like to burn when i turn on the power supply.what the problem that should i fix?

    12. Dear sir, i have another certain problem for my panic alarm circuit..here didnt sell the ac187 transistor so i have to use bc548.. when i testing, the speaker give police siren alarm when i on the supply. the microphone didnt give effect to the circuit. more than that, the bc548 which i use to replace the ac187 quick hot. what the solution and the problem for that circuit? thank

    13. 1. You can use BC 548 instead of AC187. But the output volume will be low.
      2. Timer IC 555 is used to give power to UM 3561. So at power on the timer will be triggered but after the delay time, siren will stop.This helps to know that the Alarm is working. If the 555 IC is triggering continuously, it is due to the triggering of T1.T1 gets triggering pulse from IC1.Adjust VR2 to get zero output from IC1 in the standby mode.
      3. Check the microphone for continuity. Solder it directly to the PCB with correct polarity.If you use wire for microphone, sensitivity will be greatly reduced.Adjust VR1 to get desired sensitivity.If the problem persists, replace 741 IC with CA 3140, more reliable OP Amp with same pin connection.
      4. To check the circuit behind C1, momentarily give 9 volt supply to R1.If the circuit is working, the problem is with Mic or C1.
      5. BC 548 is heating because the load( speaker ) is too high. Use a small 2 inch 8 ohms speaker.

    14. bc548 : pin no 1 collector, pin no 2 base and pin no 3 emitter
      ac187 : pin no 1 emitter, pin no 2 base and pin no 3 collector.
      when i use the bc548 to replace the ac187, should i use the pin of bc548 in my pcb or using ac187 pin in order to connect the circuit in easy pc software according the pin shown in the above?

    15. AC 187 is a high gain NPN transistor with same pin connections as BC 548. Pin 1 is collector, pin 2 base and pin 3 emitter. The pins are identified from the front side with number printed.

    16. after make correction, when i turn on the power, the alarm at the same time give police alarm sound.the both variable resistor didnt have effect the circuit. the alarm kept on and the microphone didnt work.
      i dont know what to do

    17. Sir, is that ac127 equivalent with ac187?

    18. Sir,when i on the power and the same time police siren alarm too active..so, this meant i have to wait the alarm stop after 3 minutes rite? is that meant when the delay time the ic2 which is ic555 output remain high, the component hot?just want to ensure the part i still wonder

    19. At power on sometimes the Monostable will self trigger. This has one advantage.We can confirm that the circuit is working. I will post a circuit of monostable without false triggering.Reduce the current of the power supply to 500 mA or less to avoid heating.

    20. Dear sir, at power on, the alarm too on.but,the alarm didnt stop on..i am use adaptor as the power supply.

    21. Dear sir,in order to avoid the false triggering,so i have to connect the pin 4 of ic555 with r1 and c1 rite. I have already put the all component to my pcb board. is that possible if i use a wire to connect the pin4 of ic555 with r1 and c1?

    22. Again, in this panic alarm circuit, how much the the false triggering time?

    23. Dear sir, may i know how to improve the condensor microphone?

    24. Use a high quality condenser MIC.Adjust VR1 for maximum sensitivity

    25. Thank for your kindness sir. Now, my circuit work. Thank for all

    26. Dear sir,what is the ac signal meant?

    27. Condenser MIC generates AC signals when its diaphragm vibrates due to sound pressure

    28. Thank for the comment sir.
      May i know what dc circuit of power supply suitable for this circuit?

    29. Dear sir, is that the mic and the ic ua741 is signal, ne555 receiver and um3561 transmitter in this panic alarm circuit?

    30. Sir, may i know what the block diagram of this panic alarm?

    31. Hey, i related very heavily towards this circuit for my AS coursework, however i used an op amp instead of transistors due to not having the transistors available for me to use.
      I also used a 55 to generate a oscillating light to go with the circuit to make the light trigger aswell as the siren when switched on.

      It works extremely well and the only problem i had was a slow time for capacitors charging before it functioned, however i resolved that.

      Thankyou, your circuit was very usefull.


      • Hi Bradley,

        I am currently using this schematic for my AS project this year do you know what suffix value C1 and C3 have. As in uF,pF or nF.

        Thanks for your help.

    32. Can I install output speaker with power amplifier 60W ?, I need a loud sound min. 100 dB max. 150 dB. It can make a thief will shock and run. Thanks.

      • Bradley says: on April 1, 2011 at 11:26 am

        You could install a 60W power amplifier, i have installed a 5W power amplifier to my circuit and that works to a high enough standard to be heard from atleast 200M away when it is inside a building and switched on, so 60W could be a little too loud. try a 20-30W power amplifier that should be enough for just a panic alarm. :)

    33. sir,may i ask u something about shutter guard project?in the circuit simulation,we can’t find ic um3561.can i replace that ic with ne555?any suggestion from u sir?thank you for your reply :)

    34. sir ,i am making a shadow alarm detector circuit..plz do tell me how can i connect piezo buzzer,um3561 and speakers.what is the use of piezo buzzer in the circuit..

    35. can we include gsm feature to alert the neighbours .

    36. But,sir can i used another IC to replace UM3561 becoz there ar local electronics in our country

    37. Plz is good 2 replace 741 with ca3130

    38. what is main use of this alaram tat is i need some applications about this alaram sir plz help me

    39. Thank you mr. mohankumar.. Your replies are very impressive.

    40. How to connect vr1. . Is it has any polarity.. and capacitors are whether in picofarad or micro farad.. Please reply me

      • VR1 is a potentiometer connected as a variable resistor. It has no polarity, but the direction of increasing resistance reverses, depending upon how it is wired. Capacitor values are in microfarads (uF).

    41. How to change siren generating time? And Can we use bc187 transistor instead of ac187?

    42. in panic alarm which sensor we r using says: on August 1, 2014 at 8:19 am

      which sensor is used in panic alarm

    43. apoorv devarbhavi says: on February 7, 2015 at 12:17 pm

      sir i want to do a simple but intresting project using opamp aplications .can u please suggest n guide me to do this!!!!i am a 4th sem e&c student

    44. Most if not all smoke alarms and CO detectors use a 3 pin noise maker. I want to use the noise maker in a completely different project for a hearing impaired person.
      Does anybody know how to use the 3 pins?
      Can anybody point me to a commercial noise maker with a similar pin-out? There is no number on the noise maker. I can’t tell if it some kind of piezo device.
      Remainder of detector will be recycled for hazardous materials.
      Any kind of help appreciated.

    45. Hello sir,
      In this circuit you have used an op amp with a single supply voltage.so when the circuit is on iam getting a DC offset of 3.3 volts …(I.e the voltage dropped across the positive terminal of ic 741).and iam getting a constant DC output voltage of 12 volts at collector of bc548…

      Sir,can u please explain me this fast.

    46. Sir,
      I thank u for this circuit .
      Please answer my previous question which I have posted above
      And also theres a change in the circuit ,the speaker should be connected to pin 5 of ic not directly to 12 volts.

    47. Can please any one reply to the above questions……its urgent .

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