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Thread: 4.3 Buzzer

  1. #1
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    4.3 Buzzer

    Is the TDK buzzer a speaker or just a buzzer? Seems the one I got does not work, at no point can I get it to make a buzz/beep sound. Removed from board and apply 3v it simply clicks once.

    No big deal but it could be handy but I never used the beeper on the CyberQ I have (it has a dead LCD).

    Jerry

  2. #2
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    Requires external oscillator per the datasheet. This one must be damaged or the driver is damaged.

    If I look at the driver pins from the board with a scope, what should I see?

    Jerry

  3. #3
    TVWBB Honor Circle Bryan Mayland's Avatar
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    As you've seen, it makes no sound on its own. The HeaterMeter drives it with a 12V square wave at 4kHz to make the beeps and it needs the resistor to recover from every pulse. If you look at the waveform in an oscilloscope, you should see both pins of the buzzer at 12V (or whatever the input voltage is) and when it is beeping, you'll see the pin closest to the front of the board being pulled down to around 0V every 250uS/4KHz. The other pin will show a very slight dip every 250uS, just the 12V rail recovering from the small power draw.

    You can also check the Q2 BS170. The center pin is the gate and is the inverted output waveform at 3.3V 4KHz. The pin closest to the buzzer is connected to that bottom piezo pin and the furthest pin from the buzzer is connected to ground.
    I'm that HeaterMeter guy what ruins everybody's free time.

  4. #4
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    Thanks Bryan,

    Some way I must have damaged Q2. It has been replaced and the beeper now works, lucky I had one left from another PI project......
    I Probably broke the gate internally during assembly just guessing......

  5. #5
    TVWBB Honor Circle Bryan Mayland's Avatar
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    Sweet! Glad you got it worked out. I have definitely broken the gate on those BS170s before, usually from bending them by mistake once they were installed. It doesn't help that that lead needs to be bent to fit into the footprint but that's the case for all TO-92 parts.
    I'm that HeaterMeter guy what ruins everybody's free time.

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