PWM detection instead of capacitance detection for future iterations

[s0210310]

Hi,
Big fan of the project! I was also thinking of developing a system, but this is great. While researching the issue of detecting guard hits (talking epee specifically), the question has been posed multiple times, without a good answer besides capacitive sensing, which has its obvious drawbacks.

According to this thread, https://forum.arduino.cc/t/wireless-fencing-scoring-system-detecting-a-pwm-signal-without-common-ground/686963 the patent for true wireless systems uses PWM detection to discriminate against grounded hits. Now, the issue is that without a common ground, floating detector pins will give a lot of false negatives.

But, doing further investigation (reply nr 8 here https://www.avrfreaks.net/forum/communication-wout-common-ground) 100kHz and up signal could be detected reliably.
I believe with some care it's possible to use Arduino as a signal generator to drive 100kHz PWM signal to grounded surfaces and detect it with the depressed point. I'll try and experiment with this to confirm I can detect PWM without a common ground.

Your thoughts?

[Yohannfra]

Hi,
As you can see at the end of the Arduino forum thread I talked with Luis320 in pm and from what I remember of our messages he could not get his pwm solution to work reliably enough for epee and for sabre it was too slow (from what he said).

If by experimenting you can find a way to make it work reliably it can be 100% better than capacitive sensing !

You said 'the patent for true wireless systems' does it means the pwm solution is patented and we can't use it at all ?

For you information last year I talked with @maxhaton and he tried to make it work using radio wave (see here) so this could also be a solution.

[Yohannfra]

Right now I'm sticking with capacitive sensing, I'm experimenting with the internal capacitive sensor of an STM32L152 but it would be interesting to compare all the solutions.