200 in 1 kits
I once tried to build an alarm to see if anyone opened my bedroom cupboard. Not that there was anything naughty in there - I was probably about 10 or so - but had got the idea from some Enid Blyton book.

My limited electronics knowledge meant that I attached up a buzzer then made a contact from tin foil on the door that short circuited it. On purpose.

The system technically worked - the buzzer only went off if you opened the door - but the short circuit meant the battery ran flat in about a day. Didn't explode or anything interesting mind you. Shit anecdote sorry.

Ooh just remembered another one. I attached some Meccano to a model railway transformer. I was quite convinced it would be able to pick up messages from aliens and was frightened to enter my room and made my dad turn it off.
( rob, Thu 9 Aug 2012, 18:00, 6 replies)

I recall someone making a wank alarm similar to this in a previous QOTW.

( The Mock Turtle ™ --- Thinks you are a cunt, on, Thu 9 Aug 2012, 18:02, closed)

My plan was to make it work if someone came near my door
but I didn't really know how to do it - so this was my scaled back version. A thing that buzzed if you opened my cupboard. Whoopty-doo!
( rob, Thu 9 Aug 2012, 18:05, closed)

I remember trying to capture a wasp nest in a bag once.
That would have made an awesome warning buzzer.

(The experiment went exactly as any farce writer would have scripted. )
( Infidel , shit and wrong, Thu 9 Aug 2012, 18:24, closed)

Was it
"Five go to Smuggler's Top"? Sooty had a buzzer on his bedroom door.

IIRC.
(mmm savoury snacks, Fri 10 Aug 2012, 9:41, closed)

your second story
was much better than your first.

:)
(Dan dan dan They tik urh jerbs!!!, Fri 10 Aug 2012, 13:23, closed)

you should have wired it to the mains
the buzzer would never be lacking in power, and if your door had a metal trim any intruder would have been killed for trying to challenge your security measures before the buzzer even sounded.
( ferret -> twitter.com/syfyautocorrect <-, Fri 10 Aug 2012, 14:42, closed)