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The Predictive Maintenance Tale - preview

Jan Cumps

For ' 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.

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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.

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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.

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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.

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

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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.

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

 

  • This is a great, very original idea! You covered with a single project all the chapters of the novel Slight smile

  • There's nothing new under the sun, so they say.

    Patent I filed in 1991 - uses a different piezo disc with elements on both sides but you don't need to do that - your sounder disc will do.

    On later designs we supported the disc sandwiched beteween to O rings around the periphery and contained in a metal pot.

    One issue with using this kind of disc is the very high Q resonance, which you can tame by using a low pass filter, or even a notch filter.

    The piezo material used in sounder discs is optimised for high output over a moderate temperature range.

    You get more stable (over time and temperature) results if you use different materials.

    We made many thousands of these devices which were used in the adaptive suspension system controller made for Rolls Royce cars and (for a sadly short time) some Ford cars.

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    www.freepatentsonline.com/5063782.pdf

    MK

  • in reply to michaelkellett

    There's a great quote on the side of the British Library from Stephen Fry: "Original ideas are fantastic.  The library's full of them."

    The EDSAC (and I guess earlier 1940s radar installations) used Mercury Delay Lines to "store" data.  In effect, they were just circulation tubes with the bits generated by vibrating a piezo disk at one end of a tube of mercury and a piezo disk at the other end to detect the vibration.

  • in reply to michaelkellett

    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 :)

  • in reply to Andrew J

    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.

  • in reply to Jan Cumps

    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.

  • The software is working too now:

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    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.