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RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Fri, 09 Dec 2022 13:55:33 GMT

Here a flow where both the industrial sensor and the piezo disk with michaelkellett 's front end are fed into a DAQ.

To check if the phase difference was related to the DAQ, I switched both channels.
It's not related to the DAQ. It's either caused by the front end (Michael's for the disk, inside the sensor housing for the industrial sensor).
Or by the positions of the two sensors. The industrial one sits on top of the vibration hotspot. The Piezo disk a few centimetres away.

Setup:

And a statistical view, of the piezo disk with Michael's front end only:

The acceleration calculation value isn't correct, because I haven't specified/calibrated the disk & front-end voltage vs acceleration.
You can see that the FFT graph finds the correct resonance frequency at 40 Hz.

The Predictive Maintenance Tale - piezo element voltages

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

For [mention:2136c4649d3b47f78653b7e97ac61f69:e9ed411860ed4f2ba0265705b8793d05]' 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.

[View:https://youtu.be/8hjoYlijXrU:640:360]

also check out this related post: [mention:60d0993c12fb4efcbb312da4acb7ef05:f7d226abd59f475c9d224a79e3f0ec07]

Additional Syberia art from this walktrough, from PlayStation store.

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Fri, 09 Dec 2022 13:04:53 GMT

I've been putting it to the test. Creating high energy peaks by dropping things right on the piezo.
The circuit behaves well, containing the signal within the +- Vcc:

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Thu, 08 Dec 2022 21:25:23 GMT

Better action video of michaelkellett 's charge amp/filter front end:

https://youtu.be/hOXoEsePX1s

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Wed, 21 Sep 2022 18:00:35 GMT

Action video:

www.youtube.com/.../_FsigN2DZkQ

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Wed, 21 Sep 2022 17:50:21 GMT

I've built michaelkellett's circuit.

I'm off on holidays. But I just had enough time to briefly test the circuit. Video is uploading...

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Sat, 17 Sep 2022 13:35:10 GMT

The PCBs arrived in Belgium.

Total cost of OSHPark, including production and shipping from the US: 4.93 €

Import fee from Belgian government: 19.16 €

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Fri, 02 Sep 2022 15:16:07 GMT

The goodies arrived (except the decoupling caps. I had them at home).

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Fri, 26 Aug 2022 08:48:58 GMT

BOM:

Vendor	Vendor #	type	qty	package	mf	mf code	description	url
farnell	3416403	C	1	1206	TDK	CGA5F2C0G1H333J085AA	SMD Multilayer Ceramic Capacitor, 0.033 µF, 50 V, 1206 [3216 Metric], ± 5%, C0G / NP0, CGA	https://be.farnell.com/tdk/cga5f2c0g1h333j085aa/cap-aec-q200-0-033uf-50v-mlcc/dp/3416403?st=33nf%201206
farnell	1907339	C	2	1206	TDK	C3216X7R2E104K160AA	SMD Multilayer Ceramic Capacitor, 0.1 µF, 250 V, 1206 [3216 Metric], ± 10%, X7R, C	https://be.farnell.com/tdk/c3216x7r2e104k160aa/cap-0-1-f-250v-10-x7r-1206/dp/1907339?st=c3216x7r2e104k160aa
farnell	2918843	D	1	SOT-23	ROHM	BAV99HMT116	Small Signal Diode, Dual Series, 80 V, 125 mA, 1.25 V, 4 ns, 4 A	https://be.farnell.com/rohm/bav99hmt116/diode-small-signal-0-125a-80v/dp/2918843?st=bav99hm
farnell	2447523	R	1	1206	MULTICOMP PRO	MCWR12X4701FTL	SMD Chip Resistor, 4.7 kohm, ± 1%, 250 mW, 1206 [3216 Metric], Thick Film, General Purpose	https://be.farnell.com/multicomp/mcwr12x4701ftl/res-4k7-1-0-25w-1206-thick-film/dp/2447523?st=4k7%201206
farnell	2447478	R	1	1206	MULTICOMP PRO	MCWR12X1004FTL	SMD Chip Resistor, 1 Mohm, ± 1%, 250 mW, 1206 [3216 Metric], Thick Film, General Purpose	https://be.farnell.com/multicomp/mcwr12x1004ftl/res-1m-1-0-25w-thick-film/dp/2447478?st=1m%20%201206
farnell	2849874	U	1	SOIC	STMICROELECTRONICS	TL071CDT	Operational Amplifier, 1 Amplifier, 4 MHz, 16 V/µs, 6V to 36V, SOIC, 8 Pins	https://be.farnell.com/stmicroelectronics/tl071cdt/so-08-15-jede-single-j-fet-op/dp/2849874?st=tl071

I selected components that are in stock, available on cut tape.
Actual quantity ordered: 10, 50, 100, 100, 100, 5.
Minimum is 10, 5, 5, 10, 10, 5. In that case the sum is approx. 8.5€ excl. VAT and shipping.

RE: The Predictive Maintenance Tale - piezo element voltages

scottiebabe — Mon, 22 Aug 2022 14:43:43 GMT

As MK notes in their recommendations for selecting the integration capacitor, MLCC can also exhibit the piezo-electric effect and become sensors too. So if your sensor board is really going to rattle around, it's something to consider. Although when I tried it now on my o-scope with a 10uF 16V, I didn't see much.

Just food for thought.

RE: The Predictive Maintenance Tale - piezo element voltages

michaelkellett — Mon, 22 Aug 2022 13:28:09 GMT

Here's a way of using a single supply. You need one big decoupling cap but its very hard to see any way round that. If you give the sensor a really big thump the voltage across C3 will chang so you need to pick the time constant of C3 and R3//R4 carefully.

A better performance can be obtained with an active voltage divider but thats more parts.

A really nice op amp for this would be the TI OPA375 but they are currently hard to get.

The MCP601 suggested by /members/scottiebabe would work but isn't rail to rail input so is kind of near its limit with a 3.3V supply (OK with 5V). It is noisey but this probably won't matter too much.

The NCV20166 from Onsemi looks good on paper and Farnell have stock (3528474).

I've never used them.

RE: The Predictive Maintenance Tale - piezo element voltages

michaelkellett — Mon, 22 Aug 2022 08:32:56 GMT

Absolutely fine re name.

/members/scottiebabe makes a good suggestion re. single supply op amps.

The tricky part is getting the biasing right. I'll give it some thought and post something later today if I can.

RE: The Predictive Maintenance Tale - piezo element voltages

scottiebabe — Sat, 20 Aug 2022 19:17:57 GMT

Nice little TIA circuit! If you are going to make a PCB, you may want to try making a single-supply version too.

There are lots of low-cost CMOS op-amps, ex: MCP601 nothing special about it all other than that you can still get them in DIP.

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Sat, 20 Aug 2022 16:26:12 GMT

michaelkellett, is it OK to have your name on schematic and pcb?

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Sat, 20 Aug 2022 14:31:59 GMT

KiCad schematic

edit: the charge capacitor is to be adapted to the capacity of the piezo element (see Michael's post above, and his paper). My element has 35 nF capacity. When I use a 33 nF value in the simulator, I get a response that's close to 0dB. With a 22 nF, it bops up to +4 dB

33 nF (match the input element)

22 nF:

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Fri, 19 Aug 2022 19:50:11 GMT

In volts:

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Fri, 19 Aug 2022 18:51:00 GMT

Simulation results. I saw on your website that you used an LT071, so I downloaded the model from TI, and drew an opamp symbol for it.
changes:

BAV99HM are no longer advised for new designs, suppliers suggest HY variant.
35 nF capacity for the piezo

It has been some time since I used LTSpice, the muscle memory was gone, but I got it working:

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Fri, 19 Aug 2022 17:43:37 GMT

I installed a fresh LTSpice, updated my KiCad. I'll get going now.

In the meantime, I received a second piezo element. It was on backorder since begin July. This one is 34.5 nF.

Both the original one (10 nF) and this one are measured after calibrating the LCR meter.

RE: The Predictive Maintenance Tale - piezo element voltages

Jan Cumps — Mon, 15 Aug 2022 09:39:36 GMT

[quote userid="121623" url="~/challenges-projects/project14/tales4makers/f/forum/51513/the-predictive-maintenance-tale---piezo-element-voltages/199871#199871"]I've guessed your source capacity at 25nF[/quote]

It's 10 nF. I'm going to check your circuit. Thank you!

RE: The Predictive Maintenance Tale - piezo element voltages

michaelkellett — Mon, 15 Aug 2022 09:25:37 GMT

Hello Jan,

Not very suprsied by the result or the badness of some of the Arduino and Pi support stuff - it's attracted a lot of very low end suppliers.

There is a very old charge amp/filter fronmt end ciruit on my website and I've adapted it for your sounder sensor.

I've guessed your source capacity at 25nF.

This circuit gives real and fast protection and band pass filtering and the ability to drive an ADC properly.

I've modelled it with dual supplies but you can use and RRIO type CMOS amplifier with a single supply to match the ADC. (with suitable biasing of course)

Putting the protection diodes on the summing node of the charge amp means that there is no voltage (almost) across them in normal operation so they don't screw up the LF response (which the zener across the sensor can.)

C1 and V1 represent the sensor

R1 sets a HF rolloff (dependent on the source capacity as well (yes the source capacity))

C2 sets the charge gain (if C1 = C2 the output is the same as the open circuit outpuy of the sensor would have been))

Because R1 is between the sensor and the protection diodes they will clamp the maximum input to the amplifer effectively.

The blue trace is the voltage on the summing node.

RE: The Predictive Maintenance Tale - preview

Jan Cumps — Mon, 01 Aug 2022 19:36:12 GMT

The software is working too now:

It's an abstract figure - not calibrated to the m/s^2 UOM. But it's a real conversion of the sampled data set (512 samples, taken from A0) to RMS. A sample burst is taken every 2 seconds. Arduino cloud is updated if the value changes beyond a threshold.

The Predictive Maintenance Tale - preview

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

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 ...

RE: The Predictive Maintenance Tale - preview

Andrew J — Mon, 01 Aug 2022 15:16:24 GMT

Nice one. The "timing" of the delay line on EDSAC was accomplished by making the tube EXACTLY 5' 11" long (imperial measurement of course.) This was difficult enough without temperature expansion coming into play! They ended up putting them in boxes they called coffins to try and control that. They didn't need to measure the mercury level though of course but it does seem that the piezo crystals are versatile.

RE: The Predictive Maintenance Tale - preview

Jan Cumps — Mon, 01 Aug 2022 14:37:03 GMT

Related, but with the same piezo disk playing both vibrator and sensor, this road test I did in 2015 (incidentally also while I was moving): Ultrasonic Sensing RoadTest.

It's a liquid level (and make) detector. The test setup generates a wave at the bottom of a liquid container. It reflects where the liquid stops and the air starts. The piezo detects the echo. Time of flight of that signal is measured.

RE: The Predictive Maintenance Tale - preview

Jan Cumps — Mon, 01 Aug 2022 14:20:28 GMT

I will check the patent. This is interesting.

For the Tales project, I deliberately selected the simplest piezo and the simplest protection. To make it an easy task for candidate makers.
The opamp is a little tangent - I had the circuit on my bench so I just put it in between :)