(2017 Jun 19, 09:09 PM)dan Wrote: It depends on the relay board design but there is usually a jumper between VCC and JD-VCC. The jumper gets removed and the power from the external power supply connects to GND (negative from the PS) and JD-VCC (positive from PS) The +5V line from the pi connects to VCC on the relay board, the GND from the Pi is NOT connected. This is for a low level trigger relay board.
I have tested this with a SainSmart low-level trigger (active low) 8 channel relay board and it works as expected with the Active-low relay option checked in SIP's Options > Station handling
Yes it depends on the board. I am using the 16 channel board (active low) with an infinity cascade expansion module. The +5V line from the pi does NOT connect to VCC on the relay board, but the GND from the Pi is connected. When I connected the +5V, all the relays incorrectly turned on without a signal. The 16 channel relay board gets it power from only the external power supply but the ground (the negative) from the external supply and the ground from the pi are tied together for reference.