Raspberry Pi Forums

I am trying to create a table tennis statistics controller and I need to detect when a ball bounces on the table. My first idea was to use one piezo sensor in each side of the table, but the setup was not sensible enough. I also looked to use a camera, but it was more work than I first though. I wonder if there is a good sensor that could be used in this situation.

In the second phase, I would like find the approximate position where the ball has bounced. At first, I thought that I could do this with 3 piezo sensors and triangulation, but my tests were not successful.

Microphone glued to the table.

Thanks for the suggestion. I have a few doubts before I try this path and your help is appreciated.

- How can I differentiate a ball bounce from someone speaking while playing?
- Do you have any code that can help me with this implementation?

Thanks

What didn't work with the piezo sensors?

One possible solution could be gluing accelerometers to the table, and seeing if they detect any changes (some even come with hardware monitoring for tapping).

raspbbeginner wrote:- How can I differentiate a ball bounce from someone speaking while playing?

You could consider filtering the sound signal so that you only see the characteristic sound of a ping-pong ball bouncing. Of course it will be filtered by the table already and it still might not be distinguishable from background noise.

For more advanced methods you might want to look into wavelets. That should let you detect not only the sound but also its envelope. But I hope your maths is good. The other possibility is to train a neural network. There's probably libraries available for both of those possibilities.

What problems did you have with triangulation? I've got a project in the back of my head that uses the same method.

This is Avery tricky project to detected the ball. Using sound detection , you will have to
diffirnsate between the bat hitting the ball, and the ball hitting the table.
Look into using a very fast sweeping beam detection, just very near the top of the table
This might also give you the ball touch position.

I’d be willing to bet real money that the sound of the ball hitting the table will be trivial to detect.
You just need to couple the mic to the table solidly (glue).
Try it - put your ear to the table, and have some drop a ping-pong ball on it, and compare that loudness to someone talking.

Back to the table tennis ball project.. If a video camera was over the table top, giving full view
of the compleat table, Then as suggested by others , microphones fitted under the table
using this to send a signal ( wire or wire less) to let the camera take snap/shot .This would
record ball touch and position.

All Pi In The Sky?

boyoh wrote:Back to the table tennis ball project.. If a video camera was over the table top, giving full view
of the compleat table, Then as suggested by others , microphones fitted under the table
using this to send a signal ( wire or wire less) to let the camera take snap/shot .This would
record ball touch and position.

All Pi In The Sky?

Maybe vibration sensors/switches in the table to detect the ball and send a signal to the camera?
Like this one:
http://www.amazon.co.uk/Adafruit-Medium ... B01BMRCM3W