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How can I swap a stock piezo buzzer for a louder 140db buzzer?

Discussion in 'General Electronics Discussion' started by Pretzelzzz, Oct 9, 2016.

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  1. Pretzelzzz


    Oct 9, 2016
    Hi all,

    I've bought a small proximity sensor kit and since the buzzer which came with it wasn't particularly loud for my purpose, I bought a 140db 'personal attack' alarm, that I hoped I could rip the buzzer from, and use instead of the original buzzer. Screenshot attached of the two buzzers side by side.

    However, when I interchange the buzzers, the 140db buzzer just makes a clicking sound when powered, or if the +/- is reversed, makes a low pitched buzz, neither of which is like the high pitched extremely loud buzz it is capable of if the personal attack alarm is demo'ed.

    At this point, I have very little electronics knowledge, but hoped there might be a simple answer (additional component I need to buy?) that would help me make use of the 140db buzzer instead of the stock buzzer.

    I've tried connecting the wires coming from the sensor control box either direct to the 140db buzzer, or to the battery terminals on the 140db 'personal attack' device, thus running the power through its pcb. (which I thought would originally work). The pin on the device (like a grenade) is obviously removed, so the device is always in 'on' mode, when power is enabled.

    What I do know, is that:
    -the original parking sensor kit, is 12volt.

    -the buzzer which originally came with the kit, may be 9-15v (95DB?), according to others which appear on Ebay with similar appearance.

    -the 140db buzzer uses 3x LR44 batteries, which is 4.5v combined.

    Any thoughts would be greatly appreciated - thank you :)

    (As a side note: I was also wondering if I could just use the stock horn inside the moped instead of a buzzer at all, but the horn does not sound when I connect the 12v kit to the horn. Anything I might be able to add to achieve this?)

    Attached Files:

  2. Alec_t


    Jul 7, 2015
    Welcome to EP!
    The problem is that the piezo disc you ripped from the attack alarm needs an oscillator circuit to drive it (i.e. the remainder of the alarm). The buzzer that came with the kit has the oscillator circuit built in. So it's not just a simple matter of swapping the buzzer for the piezo disc. To drive the alarm circuit you would need a 12V to 4.5V converter. To trigger the alarm from the sensor kit would require some knowledge of the circuitry of both.
    The stock horn is a high current device which the kit as is would be too feeble to power. Some interface circuit would be needed.
    hevans1944 and davenn like this.
  3. 73's de Edd

    73's de Edd

    Aug 21, 2015

    Sir Pretzelzzz . . . . . . .

    Considering that your photo is being that Minder branded unit, with its back cover off . We can see that the unit is relying upon a BLACK epoxy covered Chip On Board for the square wave electronics waveform and then is being amplified with the surface mount power transistor to its side.
    That transistor is driving an inductor or autotransformer to boost the voltage level on up and finally
    that output feed is presented to the piezo transducer via the red wire.
    A good portion of the volumetric efficiency of these piezo elements is being adjunctly associated with the resonating cavity that they use .
    Now if you are dissatisfied with the acoustical level of the present unit, first try it, using its full specified 4.5 VDC, as you are presently operating it at only 3VDC . . . . see my illustration on the cells of the unit. E.g . . .the far right cell.
    If that level is then still inadequate, I can see the further using a of 12VDC to feed the drive transistor and its load inductance, while leaving the waveform electronics at its present 4 .5VDC level.

    But I need to see the PCB's bottom . . .foil side . . . for the inductance aspect being utilized and to see where to make the magical micro snip.

    What say ye . . . . . . . .?


    Piezo Alarm Board.png

    73's de Edd


    Last edited: Oct 11, 2016
  4. Alec_t


    Jul 7, 2015
    Interesting that two of the battery cells face one way and the third faces the opposite way. That's an accident waiting to happen :eek:.
  5. Pretzelzzz


    Oct 9, 2016
    Thank you all for your replies. I'm heading to spain for a holiday (albeit stormy one!) so will reply on my return. I should mention though, that I wanted the 140db buzzer extracted from the device, and used in place of the ~90db buzzer that came with the sensor kit. OR convert the 12v power down to 4.5v somehow (resistor?) and use that to power the whole personal attack alarm, as is, instead of using the provided batteries. :) Have a great week :)
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