I have a pre-built relay module and it apparently takes around 70 mA to activate the coil. However, the relay is a low-level-trigger which requires making a connection from "IN" to GND (or GPIO LOW) to activate the coil.
In my previous builds I have been using a ULN2003 Darlington array which worked perfectly as a buffer for normal relays to protect the GPIO pins on an Arduino(MEGA and Nano), but, as the relays are pre-built and require low level triggering, I wanted to know what current I could be draining from the relays' "IN" pin and whether it would be too much for an Arduino's GPIO pin directly? If this is even a concern in the first place? (They're meant to be safe, but I am having doubts).
Also, if the current drain is too high, what would be the best way to go about this? Could I just wing it and use VCC as the on/off mechanism instead (with the "IN" pin on the relay module permanently grounded)?
- I've not had chance to test the mA being drained (the last relay I ordered was DOA).
- There are four relays so far, and each could be on or off at any one time (0 mA - ~280 mA potential).
- The Arduino GPIO pins can't sink much (~20 mA each I think, safely), and as the other pins are already being used at their recommended levels there's little room for much else without some kind of buffer.