I've been working on a project for awhile now, and I ran into a problem a week ago I couldn't solve. I'm using an Arduino uno R3.
My project involves the use of 4 relays triggered by the digital pins. Write a HIGH value, relay clicks. Write a LOW value, relay unclicks. Rather simple.
One day, I come back to it to discover it can no longer click the relays. No changes were made to my code that worked previously. The relay light came on, but no click. Could it be that I sent HIGH to 4 at the same time? My theory is that I could've drawn too much power at the same time, weakening it in a way that causes it to not output as much as it did previously.
I tested a relay on a different board and it works perfectly fine.