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  • Author Author: ralphjy
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Vibration Sensor - First Look

ralphjy

Sensor hookup

I've been reading with interest all the clever solutions to interfacing the tiny connector on the end of the vibration sensor cable.  I had also ordered the recommended SMD mating connectors.  When I received the connectors, I pretty much decided that I couldn't easily make a robust adapter so I was just going to cut the existing connector off and attach a larger Grove connector because I have lots of cables and boards that use the Grove system.  I've recently been using a lot of boards with Grove and Qwiic (Stemma-QT) connectors - most recently on the Adafruit QT Py.  I had purchased a Sparkfun Qwiic adapter board https://www.sparkfun.com/products/14495  to allow me to interface breadboard jumper cables to Qwiic sensors.  It turns out that the Qwiic coinnector is a 4 pin version of the 3 pin connector on the vibration sensor cable and that cable will plug into the adapter as I've shown below.  Of course, you have to be careful to use the correct 3 pins and I had to make SCL the GND pin but otherwise it's a mechanically robust solution.

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I printed a holder for the adapter board to keep it stable (flat) when I attach jumpers or probes to it for testing.

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In actual use I'll probably use the other Qwiic connector (obscured by the housing) with an adapter cable to a Grove connector which I can plug directly into a Wio Terminal for data collection and processing.

 

I also attached the sensor body to the mounting plate that I had printed using double sided thermal adhesive tape (because it works well as double sided tape).  And I added strain relief for the cable.  Here the mounting plate is shown attached to the riser on the microphone stand.

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First test

Before diving in to data collection I thought it would be good to sanity check my setup with a scope.

We expect the sensor signal to be about VCC/2 (+1.65V) and swing +/- around that level.

Here is a scope capture of the response to a quick tap on base of the stand.

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The quiescent DC level is +1.7V which is good.  I'm a little concerned about the quiescent noise level.

Here is a closer look at the noise:

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I then tried tapping about 18 inches away from the stand on my wood desktop.

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It will be interesting to see if I can discern footsteps on my hardwood floors.  Time to start working on a program for data collection image.

 

 

Links to my other blogs for this challenge

Person Identification using Footstep Vibration Patterns

Vibration Sensor Setup

  • It will be interesting to see the sensitivity of this sensor. The noise you see might just be background vibration. It could be tricky to try and eliminate that.

     

    Dubbie

  • in reply to zst123

    The tape might have some small effect.  The dimension before compression is 0.2mm.

     

    I’m more concerned about whether I’ll get too much attenuation because I’m not doing a direct attach to the floor.  I guess I’ll see if I need to change my method after getting some data.

     

    The main requirement for me  is to be able to distinguish unique vibration patterns.  The absolute frequencies and amplitudes of the signals is not as important.

  • Cool to see that the Qwiic connectors fit nicely! I have never used those before. image Nice mounting you have there too, wish I had a 3D printer as well!

    So far, I mount my sensor using clear tape. I realized that I must stretch my tape with enough downward pressure so that the vibrations are fully felt by the sensor. Looks like you are using a foam-like adhesive tape. Do you think it will dampen the vibrations as well and affect the results?