You however are NOT driving it at the recommended level which is Input voltage = 3V. THese are probably driven at resonance in a classic Colpitts oscillator equivalent circuit. You however are driving it at 12Vdc and later 14.4Vdc +/-? I have noticed piezo devices with the built-in oscillator driven by DC can be rated as low as 2~9Vdc. would the voltage transients quickly destroy the piezo? Generally, are current limiting resistors and flyback diodes needed for piezo drivers, and if so how does one calculate the value of the resistor?įinally, as an aside, would the piezo survive in an automotive environment (my current problems occur on the bench with a regulated supply), e.g. Is running this through 12V going to destroy the piezo? The data sheet lists the piezo at 3.3VP-P, but says it can tolerate up 30V with no DC bias. I did see much higher current spikes than expected when using ~100nF values. I tried modelling the circuit but this is difficult to do accurately when the capacitance of the piezo is unknown. Is there a way to determine the impedance of the piezo? It does not appear to be listed in the data sheet. The issues I am seeing are dying transistors, piezo volume dropping during longer tones, and the piezo failing to work for a while after playing, and then working again after "resting" for a while.Īny ideas why the transistors are dying? It doesn't appear to be getting too hot. The voltage driving the piezo is 12V, and the gate voltage is 3.3V.Įdit: Added potential simulation with Olin's suggested clamping diodes: The PS12 piezo has a 1K Ohm resistor in parallel just like the data sheet recommends. The PWM output of my microcontroller (PIC18) is connected directly to the gate of the transistor with a 100K Ohm pull-down also attached to the gate. I am driving a 4Khz ( TDK PS1240P02BT) piezo buzzer with a BSS138K N-channel logic-level enhancement FET. In my circuit I am seeing strange behavior from my piezo.
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