I was trying to get my 2-channel, 5v SainSmart relay board (http://www.sainsmart.com/arduino-pro-mini.html
) working with my Pi. I'm a bit of a novice at some of this, so I blithely followed the first online tutorial I found on the subject. The advice was to make the following connections on the main 4-pin header:
Pi -> SainSmart
5v -> VCC
GPIO -> IN1
GND -> GND
...all the while leaving the JD-VCC/VCC jumper in place. Well, it worked, sort of. Every once in a while though the Pi would become unstable, reboot, or otherwise behave erratically. I began to suspect that something unsavory was going on. I came upon this thread, and I even understood parts of it.
After watching updowndown's youtube video, things started making a bit more sense. So I promptly removed the JD-VCC/VCC jumper, and changed the wiring thusly:
(and on the 4-pin header):
And...no luck. The LED indicator on the relay lit up properly, but the relay would not energize. I tried both relay modules on the board, and neither worked. I'm left wondering which of the following options would be the best:
1. Power the JD-VCC part with a separate 5v source (not from the Pi). I'm not sure if this will help, since I'm not sure whether the problem is that the Pi can't supply the necessary 5v power to JD-VCC, or if the 3.3v is inadequate on the VCC.
2. Jump the LED's to see if that gives enough breathing room.
3. Buy another $5 SSR that is known to work just fine with the Pi (I've had good luck with the cheapo Foteks).