Important changes to forums and questions
All forums and questions are now archived. To start a new conversation or read the latest updates go to forums.mbed.com.
11 years, 1 month ago.
Piezo pickup. Impedance matching
I want to use a piezo pickup to pick up some low frequency sound. The piezio has an output with very large spikes up to 50 volts and more. I want to use the analog in on the mbed. I'll have to scale and condition the piezo signal so that it wont burn the analog in. Any thoughts on how to do it ?
1 Answer
11 years, 1 month ago.
I would say it depends on the values of your specific piezo pickup. What already might be a good idea is a resistor to the AnalogIn and a 3.3V zener diode to ground, or regular one to the 3.3V supply. That will at least protect your mbed.
Before I forget, the LPC1768 doesn't like high impedances on its AnalogIn or high capacitances. IIRC the limit on that resistor would be around 7.5kOhm.