Shock alarm circuit

 Description.

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 .

shock-alarm-circuit.JPG

Notes. 

  • 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.
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19 Responses to “Shock alarm circuit”

  • Brandon Cooper says:

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

  • aldon says:

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

  • Jishnu sravani says:

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

  • Jishnu sravani says:

    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 says:

    how can i get more sound in buzzer?

  • michael says:

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

  • michael says:

    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 says:

    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 says:

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

  • Mahdi says:

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

  • manoharan says:

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

  • Seetharaman says:

    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 says:

    How can activat piezo sensor.please answer.
    by manoharan

  • Seetharaman says:

    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 says:

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

  • seetharaman says:

    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.

  • MORRIS says:

    PLEASE I NEED SOME MORE INFORMATION! WHAT IS THE SHADED WHEEL?

  • marang thibanyana says:

    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?