how to limit 90v from Piezo Film Sensor to 3/3.3v

Discussion in 'General Electronics Chat' started by dogfuel, Jul 20, 2010.

  1. dogfuel

    Thread Starter Member

    Apr 13, 2009
    I'm using a Piezo Film Sensor
    [​IMG] MiniSense 100

    to detect vibration and am connecting to an input pin designed for up to 3.3v. This sensor can generate up to 90v (have not been able to measure anything near this).

    Playing around, I discovered that a 470ohm resistor in parallel with the sensor keeps the voltage manageable. While this seems to work for my application, what can I do to ensure that the voltage never exceeds 3.3v? do I need to worry about this?

    Thanks for humoring me on what may be a question with an obvious answer to some of you.
  2. BMorse

    Senior Member

    Sep 26, 2009
    use a couple of 3.3 volt zeners to clamp the output voltage....

    Here is an example of a circuit connected to an Opamp, and the 2 5.1 volt zeners keep the output from going above 5 volts, you can use the same setup there with the diodes, just use some 3.3 volt ones instead of the 5.1 volt diodes...


    B. Morse