# LDT0-082K piezofilm

I'm trying to have this sensor detect semi-hard impacts from the other side of a 1/2" plywood, would it cause the voltage to spike too high? I'm concerned because datasheet says it might reach high voltages on hard impact, and about the negative current exceeding the pro micro maximum rating. Should I be using voltage divider and rectifier?

Thank you!

check it first with an oscilloscope... then you can either bias it using resistor dividers or you can put a zener to clip to the top. Depends on what's important.

A small piezo has the voltage, but generally doesn’t have the current to damage a pin.
Depending on the force on the piezo ofcourse.

You should add a >= 1Megohm resistor across the piezo, to give the pin a well defined LOW.
The piezo will generate positive pulses, clamped to “VCC+0.65volt” by a pin protection dode.
The negative pulses will be clamped to -0.65volt by the other pin protection diode.

If you don’t trust the buildin pin protection (hard impacts), then add two external schottky diodes.
One from pin to VCC (cathode/ring to VCC), and one from pin to ground (cathode/ring to pin).

Leo…

Edit: Forget about zeners. A zener won’t protect when the Arduino is off.
Because max positive input voltage is “VCC+0.5volt”, and when the Arduino is off, VCC is 0volt.
A zener also doesn’t protect agains negative spikes, because the internal pin protection has a lower threshold than the zener.

I'm not too familiar with designing circuits, perhaps something like this? Imgur: The magic of the Internet

Wawa:
A small piezo has the voltage, but generally doesn't have the current to damage a pin.
Depending on the force on the piezo ofcourse.

You should add a >= 1Megohm resistor across the piezo, to give the pin a well defined LOW.
The piezo will generate positive pulses, clamped to "VCC+0.65volt" by a pin protection dode.
The negative pulses will be clamped to -0.65volt by the other pin protection diode.

If you don't trust the buildin pin protection (hard impacts), then add two external schottky diodes.
One from pin to VCC (cathode/ring to VCC), and one from pin to ground (cathode/ring to pin).

Leo..

Edit: Forget about zeners. A zener won't protect when the Arduino is off.
Because max positive input voltage is "VCC+0.5volt", and when the Arduino is off, VCC is 0volt.
A zener also doesn't protect agains negative spikes, because the internal pin protection has a lower threshold than the zener.

No, the piezo/resistor goes between pin and ground, not between pin and VCC as you have drawn it.

Try to re-draw ONE piezo circuit.
The conventional way with VCC on top, ground at the bottom, and the Arduino input pin on the right.
No need to draw two. The other circuit will be axactly the same.
Leo..