2021 Jun 22, 07:49 PM
(2021 Jun 22, 06:30 PM)astrogerard Wrote: It is a good practice to power the relays from another source. At first I would test the setup without connecting the power to the relays and only watch the behavior of the led's on the board.
So if you only connect GND next to IN1 to GN on the Pi and VCC next to IN8 to +5V on the Pi then you should be able to see led activity.
Be aware that the led will turn on when IN1..IN8 is pulled low. In SIP there is a setting called "active low" which should be set.
When everything works you can connect the extra power source to the relay part of the board (GND and JD_VCC with jumper removed)
Hope this helps,
--Gerard
**edit** Just to be clear (and safe), do not connect both GND on the relay board together. Both VCC and GND are completely isolated from each other. The Pi is not powering the relay coils, the external psu does this.
Let me update my own message. There is no need to connect GND next to IN1 to the Pi. Only VCC is enough. It is better to not connect GND to the Pi
I just checked some boards I have and these have both GNDs hard connected on the board so to totally isolate the Pi and de shift registers from the relays do not connect GND to the Pi.