What is simplest possible circuit for letterbox flap "open" detector?
MM wrote:
I want to hear an alarm sound/see an LED flash when the postie posts
something through my letterbox.
I'd say use an alarm contact with its magnet as your trigger, e.g.
https://securitywarehouse.co.uk/catalog/-p-2544.html
Or put a post-it note on the door asking the postie to ring the doorbell
whenever they deliver something :-)
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