I purchased 2 "Mechanical Relay Board, 8 gang, 10A 220VAC, 24VAC 30ma coil" relay banks that I am trying to control from a raspberry Pi. To do this I've built out 2 595 shift registers and I'm using an external power source, not the power from the pi.
Testing on LED's everything is ok but for the life of me I cannot get the relays to activate. I figured that maybe the input was too small, not enough mA to activate it.
I'm supplying 12v DV from a 12v 1A transformer to power the relay bank and I tried to activate the relays using 5v from USB, 5v from 9v battery running through a 5v regulator, 9v directly from battery and also 12v directly (from the transformer used to power it).
Nothing. I notice that when I test the voltage across the input power terminals, it reads very low (0.10v) but when I unplug the adapter from the relay bank, it reads 12v. So when the power is plugged in to the relay bank, I'm imagining that the bank is causing a fault in the transformer? I noticed that when I had the 9v battery plugged in to the bank as the power source it got really hot.
What am I doing wrong? I changed the jumpers to both positions and tried the same tests on both setups.