“Those of you who like to play Ping Pong know that a serve in which ball touches a net before hitting the opponent’s side of the table is a faulty serve (or a “let” in the official speak). You also know that sometimes the ball touches the net so lightly that it is hard to say whether it did or did not.
The idea is to build a faulty serve alarm by attaching a vibration sensor to the side of the net, and creating a small device that beeps every time a ball (or something else) hits the net and makes it vibrate.
To make this practical and less annoying the device should:
Beep and flash an LED when net is disturbed
It should only beep once and pause for a reasonable time (at least until the net is not vibrating anymore)
Beep only after a certain level of vibration is detected (thus avoiding false beeping on small vibrations caused by the ball bouncing off the table)
I found this to be a perfect candidate for an Attiny85 based device.”