Doubt with Piezo sensor parallel resistor

Hi!

I'm trying to make a Midi controller for a Roland drum pad, some measurements with the piezo gave me voltages up to 6-10 Volts peak, but pressing it really hard. Reading some topics people usually talk about 50-90 volts with their sensors.

Using a 4,7MOhm resistor will increase the sensibility of my sensor? Or should I use a lower + reference (1.1V from the AT) to increase the resolution of the ADC?

Thanks in advance!

First thing you need to do is make sure you do not exceed the 5v limit on the input pin! Possibly use a 4.7v zener diode to limit the input.

Putting an R across the sensor will not increase its sensitivity. The sensitivity is a function of the design of the sensor.

Weedpharma

weedpharma: First thing you need to do is make sure you do not exceed the 5v limit on the input pin! Possibly use a 4.7v zener diode to limit the input.

Putting an R across the sensor will not increase its sensitivity. The sensitivity is a function of the design of the sensor.

1) Not a problem with common 1" piezo disks. They don't have the current capability to damage a pin. The input pin protection diodes clamp the voltage spikes.

2) A piezo is basically a capacitor. Without the resistor there could be DC on the piezo. A resistor to ground keeps the piezo at zero volt, so you can measure the actual pulse.

1Meg to ground could add to wiring/hum problems.

The voltage spike on a piezo could be positive or negative, depending on how the piezo has been dropped onto the brass disk in the factory. If you're serious about it, you should measure it.

I do this with the piezo resting on an O-ring the size of the piezo, and a DMM on the lowest voltage setting. I gently/slowly press the center of the piezo (face up) with the red wire of the DMM, while holding the black wire onto the brass. You either see a positive going voltage or negative going voltage when pressed, and the opposite when released. You should have a positive going spike when hitting your drum pad, so a piezo with a negative going voltage when pressed with the above method. Assuming you glue the piezo disk with the brass side to the drum pad. You have a 50/50 chance of getting the right piezo. Leo..