Vibration/Shock Sensor

[Pensive]

Hi guys

Any ideas on a good shock sensor solution? I have arcade buttons and wish to detect how hard one has been struck, by matching up a shock sensor reading with the button strike I should be able to determine strike velocity fairly well.

Any cheap solutions?

Rgds

Jon

 

[pictographer]

Piezoelectric diaphragms would work.

 

[Pensive]

Just one of those, wired into an analog port? Surely that's too easy

This example uses 2, with a pull down resistor

http://bridell.com/how-to-use-a-piezo-element-as-an-arduino-sensor/

Can I get away with one or should i follow the tutorial? My electronics is my weak point....sorry

 

[pictographer]

I've been playing with one on my desk, but I'm just a beginner myself. You can read something wiring it directly to an analog input, but I don't know if that is safe (for the Teensy) or gives you enough sensitivity. If you need to distinguish banging on one spot from banging on another, you'll probably need multiple piezos unless you combine the shock reading with an ordinary button reading.

Regarding the circuit, I imagine all the cool kids whip up some op-amp circuit complete with over-voltage protection diodes and a multi-turn trim pot so each sensor can be tuned to report the same range. I'd only go for the op-amp if the Teensy's analog in isn't sensitive enough or it was time to learn about op-amps. ;-)

At Maker Faire some years ago Paul created a force sensing mat so kids could change the pattern on a big LED array by jumping and stomping. Maybe he blogged about it somewhere...

 

[stevech]

I've used a low cost ball-in-tube sensor. This is a passive device. A tiny cylinder perhaps 1/3 inch long. Inside is an etched gold ball rolling on an etched interior of the cylinder.
Several vendors. I got some samples from signalquest.com. Here's one of many they make
https://signalquest.com/product/components/sq-sen-200/

I connected its two leads to an I/O pin on my microprocessor, to create an interrupt on contact closure. The microprocessor ISR increases a count on each interrupt (stopping at 255). A non-ISR code driven by the recurring timer clock interrupt decrements the same counter. If the counter is > x, there is significant vibration/movement.

I put this on a vault door. It reliably reported both hammer-strikes on the door handle and opening or closing the hinged door.

In the lab, I put the sensor on a table top, in a hunk of plumbers putty. Tapping a #2 pencil's eraser lightly trigger counts.
It would do well also as a car-in-motion detector - simple.

There a lots of forms of ball-in-tube sensor. Some mount for V or H sensitivity. Some have a hump in the middle. Some are made so that half of the cylinder is not a conductor, so it becomes a tilt sensor - as might be on a garage door sensor affixed to the door with an adhesive and connecting to a low cost wireless radio.

SignalQuest is high quality. You can find cheap ones on eBay and china importers' web sites. I think SparkFun has one too.