I want to hear an alarm sound/see an LED flash when the postie posts something through my letterbox. The letterbox has a flap on the inside to keep draughts down. I want to attach 2 contacts to the flap and body such that as soon as the flap opens and the contacts are broken, said alarm/LED are triggered.
I'm worse than a novice in electronics, although I've painstakingly soldered Velleman kits and similar before. I don't know the first thing about circuit design, but I know enough to know what a resistor is and what the coloured rings represent. Also, capacitors, transistors and, above all, DIL chips such as the CMOS 4000 series.
I've reviewed several circuits on the internet, but they all seem overkill for what I need. The problem, it seems, is getting the thing to trigger when the circuit is OPENED.
Thanks.
MM