I've had several freezers with "door open" alarms but they've been all
been f***ing useless. Door wide open when I'm rearranging stuff? Beep
beep bloody beep, yes, thank you, but it's obvious the door's open isn't
it? Door half an inch open because one of the drawers isn't quite
pushed home? Silence.

Thermometer-based alarms are useless because they routinely go off
during the automatic defrost cycle.

The problem with the makers' "door open" alarms are that they work on
the hinge side so they're spectacularly inaccurate. What's needed,
*obviously*, is a switch at the opening edge of the door. But it seems
to be beyond the wit of the manufacturers to understand that or to put
it into practice.

end rant

I did try making my own "door open" alarm many years ago, using a timer
operated by a microswitch stuck on the side of the cabinet with a lever
between the cabinet edge and the door seal. I can't remember why but it
wasn't very successful, probably not robust enough for a kitchen
environment.

I wonder if some sort of magnetic detector might work better - there
are, after all, magnets in the door seal. Or perhaps a low-profile
keyboard-type switch between the cabinet edge and the seal? Or any other
ideas?

--
Mike Barnes