I have a KNACRO DC 5V 2 Channel 30A Relay Module that I'm trying to control using an Arduino. I believe the code is fine, I have checked it with a multimeter and it's sending the signal as expected. However, the relays are not activating. The minimum signal current is 3mA which I'm successfully meeting. How should I be wiring the relay module to the Arduino?
Those are 12 Volt relays and will not work on 5 volts. They need
a separate 12V power supply.
Did you follow the guidelines here?
http://www.knacro.com/dc-24v-1-channel-30a-relay-module-optocoupler-isolation-high-low-level-trigger/
DC+ and DC- are not supposed to be connected to the processor. You can have a common ground (but don't need it, since VREF provides the ground return for the control signals). But these are not 5V relays. They are 12V relays. Look at the writing on top of the relays. DC+/DC- must be connected to an auxiliary 12V power supply.
Thanks for providing adequate information. Too often the patient must sit in the chair while various dentists pull teeth. 