The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Mon, 15 Aug 2022 08:42:30 GMT

For balearicdynamics' Tales for Makers Amusement Park, I'm making a predictive maintenance design for the rides and Ferris wheels. They have to be kept safe and in good condition.

The project is a little piezo buzzer. In this little forum post , I show that these can generate high voltages that can damage microcontroller inputs.

The artwork in this story is an ode to Benoît Sokal. Comic Artist and Designer of the Syberia game.

A piezo transducer can act as speaker or sensor. I'm using it as a sensor. Piezo can generate high voltages - an element is used to generate the spark in piezoelectric stove igniters. Although these high voltages aren't generated when measuring usual mechanical vibrations, a protection circuit is advised. Even a medium tap on the sensor generates 10s of volts.

image source: product page of the kit I bought on Conrad

There are breakout kits from several companies for Arduino and Raspberry Pi, that come with a piezo element and a protection circuit. They all seem to deploy the same protection circuit:

The diode is a 5.1V Zener Diode. But let's see what happens if I hit a test probe on the board where sensor sits on:

It's a "plastic on cardboard" action. I can easily generate 24 V peaks with the protection circuit in place. Not good for a 5V UNO. Most likely unhealthy for 3.3 V Arduino MKR or Raspberry Pi. If this would be mounted on metal, and a metal part would be used to hit, I'd expect the peaks to go higher. There's almost no energy - it's all voltage and for a short time. But it's voltage that often does the damage.

https://youtu.be/8hjoYlijXrU

also check out this related post: Piezo disk as Vibration Sensor: input buffer and filter

Additional Syberia art from this walktrough, from PlayStation store.

The Predictive Maintenance Tale - preview

Jan Cumps — Sun, 31 Jul 2022 19:02:34 GMT

For balearicdynamics' Tales for Makers Amusement Park, I'm making a predictive maintenance design for the rides and Ferris wheels. They have to be kept safe and in good condition.

The project is an Arduino MKR Accelerometer that will send vibration info to the Arduino Cloud. The amusement park staff uses this to spot trends and changes in the gearboxes, motors and axles of the rides.

I'm late with my project, due to moving (and losing some components while doing that). This little forum post is a preview of the hardware that monitors the vibrations.

The artwork in this story is an ode to Benoît Sokal. Comic Artist and Designer of the Syberia game.

Not long ago, I reviewed an industrial piezo vibration sensor for a road test. But for experiments, you can also use a simple piezo buzzer. That's what I'm doing for this tale.

They are normally used as buzzer in instruments and doorbells. But they are good vibration sensors. Attention though: these piezo elements can generate high voltages. They are the same things that are used in cigarette and stove lighters to ignite the gas. An input protection circuit is needed.

This circuit should be good enough for an Arduino UNO, keeping the signal close to the power rail. But I'm using an Arduino MKR WiFi 1010 - and that can't have 5V a the analogue input. The circuit also doesn't deal with (smaller) negative component of the signal generated by the piezo element. A fast recovery diode will deal with the negative, and I've put an OpAmp in place to buffer (and later attenuate) the signal. This is more an excuse to validate my lab instruments after the move than an economical protection and attenuation design.

This is where I am with the hardware part at the moment.

This is the same shaker that I used for the industrial piezo sensor for the road test

I made better progress with the software. I've made a fast ADC design (with DMA support on the Arduino) and a function to calculate acceleration. The knowledge from the road test came in handy. I also have the Arduino Cloud part working, where I can collect the acceleration telemetry and show on a dashboard.

The real blog, with hardware, firmware and cloud setup will follow. Hopefully within the deadline ...

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The Predictive Maintenance Tale - piezo element voltages

The Predictive Maintenance Tale - preview