I have succesfully connected an MCP23017 to my Arduino Mega and got it to blink a LED using a 330 Ohm resistor. Now I am trying to drive the relay's on a Velleman K6714-16
I connected the output pin through a 330 ohm resistor to an input pin on the Velleman K6714-16 and connected the ground pin of the Velleman card to the common ground. For some reason this works for about 5 blinks and then the MCP23017 is blown up. If I use an Arduino digital output pin instead of an MCP23017 pin everything works fine.
I think I do something wrong with the wiring.