Shock alarm circuit

admin April 7, 2010 22 Comments


Here is a simple shock sensitive alarm circuit that has many many applications fro home to automobiles.The main application of this circuit is to use it as an anti theft alarm in automobiles.A peizo electric sensor is used as the shock sensor which has to mounted on the door which you have to protect.

Here the IC1  LM 3558 is wired as an inverting Schmitt Trigger.The POT R1 sets the threshold voltage of the circuit.R1 is used as a feed back resistor.When not activated the out put from the piezo sensor will be low and so do the output of the IC.When the piezo sensor is activated its output voltage goes high and triggers the Schmitt trigger.This results the beeping of the buzzer.The buzzer remains beeping for some time even if the vibration is removed.this is because the increase in the inverting input has little effect when the IC is triggered and the state can’t be easily reversed.

Circuit diagram with Parts list .



  • A 3 v battery can be used as  power supply.
  • Fix the sensor firmly to the surface,where ever you place it.
  • It is always good to place the sensor near to the door knob.
  • Adjust R2 to obtain the required sensitivity.
  • Assemble the circuit on a good quality PCB or common board.
  • Use a IC holder for mounting the IC.
  • rose
    June 14, 2015

    sir,are all the components required for the circuit available in scrap cfl lamp? if not ,then what all components we need to buy.

  • Brandon Cooper
    April 29, 2013

    @Jishnu find a suitable relay you can then control a bigger buzzer or bell.

  • aldon
    August 20, 2012

    my circut is ready and working fine how to increase output can we use 9v battery

  • Jishnu sravani
    April 14, 2012

    is it fine to use 9V battery instead of 3V in this circuit??
    reply me soon
    thank you

  • Jishnu sravani
    April 14, 2012

    Hi can u please tell me how to get more sound from the buzzer?
    its important please reply me as soon as possible
    thank you

  • Eniyan
    March 13, 2012

    how can i get more sound in buzzer?

  • michael
    March 12, 2012

    gud day, is it possible for a normally open SPST swtch to replace dat shaded wheel?tnx

  • michael
    March 11, 2012

    gud afternun Mr.Seetharaman is it possible 4 dis circuit to use as a mototcycle theft alarm?
    waiting for ur responce….thank you

  • rajat dhumal
    January 23, 2012

    and make sure that u make use of an expert hand to handle the delicate circuit…or else u’ll be losing hefty bucks…

  • rajat dhumal
    January 23, 2012

    go for a ready made assembles circuit…this circuit is too sensitive and not serving for the purpose…

  • Mahdi
    December 16, 2011

    I want a circuit that I want you to electric shock in the lower body would exert

  • manoharan
    May 17, 2011

    Hi Mr.Seetharaman,phiezo sensor is produce emf. This is enable answer.Thank you very much.

  • Seetharaman
    May 17, 2011

    Hi manoharan if a phiezo sensor is stuck on to the door, on the boot, bonnet at suitable location inside. once any body tries to pressure or hit with hammer etc the sensor will produce emf out put. that is further taken care by the above electronics.

  • manoharan
    May 16, 2011

    How can activat piezo sensor.please answer.
    by manoharan

  • Seetharaman
    April 12, 2011

    Hi Elgardo Piezo buzzer is a programmed one will produce only one type of sound / music. sensor / sounder are like solid state loud speakers without any voice coil or cone paper etc.

  • Edgardo Diolola
    April 11, 2011

    Is this piezo sensor the same as the piezo buzzer?
    Thanks in advance.

  • seetharaman
    June 10, 2010

    Hi friends The shaded wheel is ceramic transducer, the impact sensor. It can be from a old telephone receiver or from any loudspeaker having HF ceramic tweeter. The ceramic tweeter can also be bought in the market as HF transducer with red and black wires connected.

  • June 9, 2010


  • marang thibanyana
    May 11, 2010

    this is nice except that ther is somethin i will need you to forward to my mail. whats that shaded wheel connected to the ic1 LM358 operation amplifier?

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