1 Topic by jdunne525

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This project creates a different type of “microphone” that isn’t triggered by sound, but instead by vibration (or a physical shock) such as a net moving after something hit it (golf ball, baseball, disc golf disc, or whatever you want as long as you can attach this device and it causes a movement).  This new “microphone” goes into a standard microphone jack on any computer and can be used with Kinovea’s audio trigger feature to trigger a video recording. 

The upside to this is that we can trigger Kinovea in a much more reliable way that doesn’t give nuisance trips by other noise in the room as the audio trigger tends to do.  (It can of course still have a nuisance trip if somebody hits the net, but that's a whole different issue)

No special software (besides Kinovea) is needed.  This is purely a mechanical replacement for a standard microphone.

Take a look at what I made here:
https://github.com/jdunne525/KinoveaVib … ree/master

2 Reply by joan

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This sounds great! The link doesn't work maybe the repository is on private?

3 Reply by jdunne525

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Ah, thanks for pointing that out.  I've corrected it now.

4 Reply by joan

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Very cool. Reading your original post I thought this was like a contact microphone but in your case it can just hang on a net and get triggered by distant movement, quite interesting.

How sensitive is it? If we put it on a high jump mat for example, would it trigger from the jumper falling on the other side of the mat? Or if it is attached to a net like in your picture and someone else passes by quickly, does it trigger from the small wind?
Maybe it could also be used to detect water surface breaking in diving.

Actually this makes me think there could be a function where the trigger is used to increment a counter instead of starting capture.

5 Reply by jdunne525 (edited by jdunne525 2025-01-11 20:10:52)

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It's hard to describe how sensitive it is.  Calling it a vibration sensor is a bit misleading.  I'd call it more like a shock sensor.  It certainly won't trigger by minute vibrations.  Say I put it on my desk.  I have to hit my desk somewhat hard to get the sensor to bounce enough to get it to trigger.  It doesn't trigger by air currents blowing around unless you blow pretty hard and get it to wiggle back and forth.  The sensor has a metal pin in it that makes the mechanical connection and it takes a bit of force to get it to dislodge.  If I give it a gentle tap with my finger it breaks the connection.  I would imagine it would probably work for a high jump mat, assuming the mat has some movement where you're placing it. 

Detecting water surface breaking from a dive sounds a bit more tricky.  That might work, but I think you would need to place it on a float that would bounce back and forth quite a bit when a wave hit it.  I think a narrower float would be better to get more movement.  Better still mount the sensor on a pole sticking up from the float so it wobbles back and forth more and amplifies the movement.

I found a YouTube video with a demonstration of the sensor that should help give an idea of sensitivity.  (This has a module with some electronics built around it, but the sensor is the same).
https://youtube.com/clip/UgkxhHQdHwc--q … 2iTqhLJ9hz