I am new to ALL of this so please bare with me.
I currently have 3.3vdc coming out of one digital pin (OUTPUT set to HIGH) into a relay then out and into another digital pin taking the current as input (INPUT set to LOW). When other (5V) circuit is energized the relay is closed and allows the 3.3v to travel from the output pin to the input pin, thus triggering an action in the firmware. I could probably use an optoisolator here as well, but for now it’s a simple 5V 1A SPST relay.
My questions are this…
- Do I need to ad anything to the 3.3v out/in circuit to slow the current flow?
- I am still confused on the PULLUP/PULLDOWN resistor thing. Assuming this configuration is acceptable, what do I need to specify for the INPUT pin, INPUT_PULLDOWN or just INPUT?
Thanks for your help!