I have a opto-isolated SPDT relay with the lamp I am controlling connected to the normally open [NO] contacts. That means when the Spark-relay combo has no power the lamp is OFF. To keep the NO contacts open (to keep the lamp OFF) the input signal must be HIGH. This I found surprising but apparently it is how most relays usually operate, is that correct?
My issue is this. When I power up the Spark-relay combo the lamp comes on for a short while because the default state of the D0 pin is LOW, until my app kicks in and raises the signal HIGH. I would prefer the lamp stays off until the program kicks in.
I’m familiar with pull-up and pull-down resistors for analog signals. Can I wire up D0 such that D0 is normally HIGH, at start up?