What are the best point to source power?
I'm attaching a targeting laser and a switched air-pump to my system.
I know about the pin for the M7 signal, but my SSR has an activity/status light and needs both Vcc and Vgnd as well as the control line. Likewise, while the targeting laser is very low power and switched by an external switch, it needs a stable Vcc and Vgnd.
What is the best point on the board to draw these from?
One concern is to make sure that the M7 signal is coupled to the right relative ground (do we have a common earth level across the whole system?)
Yes you should be able to use the power from the laser supply. The M7 signal goes from the MCU to an opto coupler which is getting its power from the laser supply (hot side). The MCU side is decoupled via opto couplers so don't use any pins on the cold side.
Thanks! I had been using the +5V on the (optional) Alternative Limit Input (bottom right on the board layout diagram) but I wasn't sure if that was safe.