I have a mailbox alarm circuit that transmits a message to my receiver whenever the mailbox door is opened. The UNO circuit is powered up by the door opening and power is cut when the door closes. It works mostly, but, I believe a very fast open/close doesn't give enough time for the transmission to take place.
Is there any way to keep the circuit powered up beyond the door closing (relay? second power source?) to ensure it finishes? If I could hold a relay open for 30 seconds, that would work.
For obvious reasons, I don't want the power on 24/7.
Thanks for reading this. Circuit/code upon request.