Need help with a Relay for Moteino M0

[bsj8377]

Hello all,
I just got two Moteino M0 with RFM69's for a wireless project. The reason I picked the Moteino M0 was because it had a DAC on it and that is needed for this application. One other thing I need is to add a relay to one of the digital outputs...however, I'm a little confused on what the Moteino M0 can support? I searched around and found something about low power and high power mode, but even in high power mode it said that each output could only support 7mA. I can't find any relays that only require such small current?

So my questions are:

1. Is 7mA the max, and does that have to be set somewhere?
2. What is the recommended way to add a relay to the Moteino M0 boards?

Any help is appreciated...thanks!

Brian

[Felix]

Hi Brian!
You would never want to drive a relay directly from a MCU pin.
Instead you would want to use some kind of transistor to drive the coil of the relay. Ideally you could use an optoisolator if your supply rails in the low power side (the microcontroller side) needs to be kept "clean" from switching noise and other harmonics that might be coupled back from the "dirty" relay side.
When I hear you're dealing with the DAC that might be the best approach. But don't fix something until it's broken is my approach, try the transistor first then use the optocoupler if it becomes necessary.
Here's a stackexchange thread that discusses this and a solution.

[bsj8377]

Thanks Felix!