I am building a speed-testing stand for electric wheelchairs with an arduino nano + rotary encoder. The wheelchair is put on cable caddies, which turn the rotary encoders via a belt.
The setup itself with measuring the speed works pretty well. However, due to the rubber wheels on the metal caddies, charge builds up and then there is a static discharge (you can see the flash), which freezes the arduino.
So far, I don't have any protective circuit for this. The arduino is connected to power with a USB-Powersupply. The rotary encoders get their power from the VCC+GND Pins of the arduino. The data pins of the encoders are connected to the arduino digital Pins 4 + 5 (defined as INPUT_PULLUP).
What is the best way to protect the circuit from these voltage spikes / static discharges? There isn't really a way to ground the cable caddies, because they are portable and set-up in sport-halls with plastic floor.
Any hints will be greatly appreciated!