Piezo Vibration sensor problem

Hi guys~

I have been working on arduino + piezo vibration sensor to detect the stress amount. Basically the sensor will attached to helmet and when the rider crashes and hits his/her head to the ground the sensor will detect the amount of vibration and sends information to the android application. And the application will compare the range of vibration, if it higher than the limit then the application starts calling 911, police or the riders' relatives. I have two types of piezo vibration sensors: Piezo Vibration Sensor - Small Vertical and Piezo Vibration Sensor - Large with Mass.

The problem with both sensors is that they are extremely sensitive. As you know analog inputs read from 0-1024 (0v-5v), however, since the sensor is too sensitive for a small touch it gets to the limit (1023)

Is it possible to make them less sensitive, so that I could set the range ex.: if the hit level is less than let's say 300 then do nothing. if the amount is higher than 500 then think it as an accident and call these numbers.

FYI, I also used diodes to convert negative voltage to positive.

Your help is much appreciated. Thank you!

Piezo sensitivity would be easy to control simply "loading" output. Put a resistor in parallel, resistors value would define sensitivity.

Indeed - piezo elements behave approximately as current sources, so the voltage pretty much can be whatever you want - the smaller the load resistor the lower the voltage. Try 1M, 100k, 10k and you'll get some indication of what sort of value is best for your application.

Hi guys thanks for the reply and sorry for my late response.

I was really working hard on my project.

I knew that using resistor would lower the sensitivity, but the main problem was exactly where should I use it. Cos I tried millions of options but whenever i tried to connect the other end to the ground the current was 0. It stopped working.

If you can, please guide me to build the circuit so I could use the power of resistor to lower the vibration sensor sensitivity.

I know for you it is so simple, but for me it is nightmare.

Thanks in advance

Alex

Resistor goes across the output from the piezo element - think of it as converting a current into a voltage.