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  • General purpose circuit of the simple pressure sensor alarm is built around a couple of readily available cheap components. Working of this circuit is straight forward and self-explanatory. When the circuit is powered by a 9V compact battery, the active piezo-sounder at the output of IC1 starts beeping for a short time and then goes into idle state.

    Whenever, the pressure sensor element (Piezo-ceramic wafer) is gently tapped, mosfet T1 is fired by the electric pulse from the sensor through related components and IC1 is again enabled by T1. As a result, the piezo-sounder starts beeping for a short duration, set by the in-circuit values of R3 and C2. Piezo-sounder at the output of IC1 can be replaced with a low current 6 to 9 V electromagnetic/solid-state relay to control external loads. Likewise, values of components T1,R3 and C2 are not very critical.

    You can experiment with another values to “tune” the circuit as per your requirements. Pressure sensors (in piezo-wafer form) are widely available with reputed hobby electronics components dealers.

    Possible Applications of this pressure sensor circuit:
    Automatic Door Bell, Carpet Alarm, Hit Switch, Knock Bell, Garage Alarm, Doormat Sensor…

    Pressure Sensor Alarm Circuit Schematic

    pressure sensor alarm circuit schematic

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    16 Responses to "Pressure Sensor Alarm"

    1. am wondering if this cicue could be adapted to operate a triac, then a relay to turn on a 120ACv well pump. If so, how

      • T.K.Hareendran says: on October 17, 2010 at 4:00 pm

        Use a low-power SCR,like BT169, at the output of IC555 to drive a 6-9V dc electro-magnetic relay.Next,you can switch a heavy-duty relay through the 1 C/O contacts of the first relay.

      • Thank you, this what I thought, but like so many other things I THOUGHT and then applied that didn’t work,, thought I would check it out on this site first before burning more parts with trial.
        After I have applied this system,,, would you know of a touch sensitive “low voltage” circuit to apply to the previous low to high relay circuit’ I would like this touch circuit to operate by me touching the plumbing faucet and using me to complete the ground there-by activating the wellpump.

    2. Pentaconto says: on October 15, 2010 at 11:00 am


      And the schematic diagram of this circuit, where????

      Geetings from Barcelona (Spain)

    3. Sir , can we use the same piezo electric element that we use in buzzer as a señsor i.e. Piezowafer …
      Pls reply soon …

    4. Sir , can we use the same piezoelectric element that we use in buzzer as sensor

    5. Anantha says: on May 7, 2012 at 8:33 am

      Will it be possible to use a counter instead of a buzzer. If yes, do I need to interface it through something?

    6. does this circut work?

    7. the piezo buzzer is beeping even if no pressure is applied……wt could be the prblem?

    8. can i get the documentation of this?? plssss

    9. BUZZER IS BEEPING even if no pressure applied

    10. Buzzer is beeping if no pressure is applied…what will be the problem

    11. Abdelrahman says: on December 25, 2014 at 5:14 pm

      Can We replace T1 (MOSFT) with a bipolar transistor?

    12. Hanumant Vani says: on December 31, 2014 at 8:22 pm

      for this model i need 3 pressure sensors but it is costly in market. So suggest me alternative or which sensor should i use.? And you have circuit diagram of this pressure crt. ?

      • Jim Keith Jim Keith says: on January 1, 2015 at 4:48 pm

        @Hanumant, check out the Freescale MPX2300DT1. It is available from DigiKey for $5.38 each. Pressure to 300mmHg. Circuit is a resistance bridge that is powered via 6V. Interface requires a differential amplifier (op amp).

    13. Deepak Bhushan says: on April 1, 2015 at 8:24 pm

      sir I want to know about piezoelectric shoe charger. Please give circuit diagrams. Also I want to know how adc dc boost rechargable battery and piezo plate would be connected.
      Sir please help.

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