I'm using Numato 16 GPIO board to switch relays on 8 Channel Relay Module. Until no 220V load is connected to the relay all works fine and I can switch on/off relay using Serial port command to GPIO as many times as I want. But once I connect actual device (in my case pump) through the relay - relay switches on (or off) the device and GPIO board stops communicating through COM port. After reconnecting GPIO USB cable it works again one time. Is my micro bieng stung by arcs radiating? Do I need some sort of snubber?
Previously I had GPIO Board feeding from USB, but was experiencing exactly same problem. Thought maybe it's not getting enough power from USB so rewired to use external 5V supply as it is now.
I wonder maybe somebody had similar problem or has an idea what can be done to solve it?