Goal: To create a board that sits in a fridge and monitors when the door is closed. When it is closed, it must determine whether the light goes out correctly and does not come on. If it does come on then the fridge is obviously consuming more electricity than it needs to so an alarm must sound to alert the owner.
Help: Where can I start?
drill a hole in the door and insert a piece of glass
Erik
How about just deducing everything from the activity of the compressor?
Or measure the current consumption and figure out if the fridge draws too much when the compressor isn't running - which would be the current for the lamp.
Or locate the power wires for the lamp and check if current flows through them.
ah, this is dead simple.
open the door and quickly grab the lamp, if it is warmer than the fridge ambient it was on.
no need for a Rube Goldberg solution
Couldn't you just wire a buzzer along with the light? Or put a camera in the fridge if you wanted to observe what happens after the door closes?
If the light comes on the door switch has failed.
If I wanted to evaluate my fridge's power consumption I'd use a Kill-A-Watt type device.