Interfacing circuit for Piezoelectric vibration sensor to detect shock

Thread Starter

Sudip Mandal 2

Joined Mar 29, 2017
24
I want to detect the mechanical shock of a machine. To measure the vibrational shock I am using Minisense 100 Piezoelectric vibration sensor. I have done the feasibility test using it and it is giving output as expected. I have observed on the oscilloscope output frequency for all type vibrational intensity and I came in conclusion that I want to sense only range between 50Hz to 100 Hz. For this frequency range, I want to create a 3.3V digital logic to interface with a microcontroller digital pin.

I have designed a bandpass filter using LM358AN and a comparator. My circuit in below GIF.jpg
I didn't get any output from it. Please let me know what's wrong in this circuit?
 

Audioguru again

Joined Oct 21, 2019
542
Why is the input resistor to ground the extremely low resistance of only 3.3k when the video shows 3.3M (1000 times more)? But a lousy old LM358 opamp will not work properly with 3.3M. With a 3.3V supply its output high is only about +1.9V.

Also, the very simple bandpass filter has a droopy response with gradual slopes. The lowpass cuts most of its frequencies and the highpass also cuts most of its frequencies. Even mid frequencies of the bandpass are reduced a lot.
 
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