Have used this controller many times before and use 12v dc to power brd. Just recieved new controller and your basic 2 channel SPDT relay carrier with 12v relays model # 2487.
Everything works fine with usb connected to computer 12v powering brd and relays.
When i disconnect from computer the relay board rattles like a short.
If i use a 9v battery to power board it works fine not connected to computer.
I thought you can use up to 16 v to power board and i have used 12v many times before.
Any info would be great