Unfortunately, there is one male that insists on marking our front door. Every. Freaking. Night. There are few smells in the world more pungent than that left by a territorial cat. My boyfriend was at the end of his rope and wanted to trap the cat to turn over to animal control - a solution that didn't sit well to me as I know that amounts to a death sentence. So, to the drawing board where I came up with my pressure switch triggered Sonic Critter Deterrent. It went off 4-5 times the first night, and we haven't seen or smelled the cat since.
Step 1: The Supplies
Door alarm (got mine at the local dollar store): $1.00
2 pieces of cardboard or box (I found this box that the post office left at the office last year to introduce their program, it is a size we never use): Free
Aluminum foil: Pennies
Weather stripping (this was left-over from fixing a laundry room door): Free if scrap, A buck or so if purchased
A small amount of wire will be needed, your soldering gun, some spray adhesive, a bit of copper or aluminum tape
Step 2: The Alarm
Instead, I snipped & stripped the other wire, then soldered a piece of scrap wire to each side in order to extend them. I ended up with two longish wires coming from the side of the alarm. I wrapped the connections in electrical tape to ensure they didn't touch and short the connect before my new switch.
Step 3: The Switch
I used spray glue to attach a piece of foil to the inside top & bottom, then put a length of the weather stripping along each side. The rubber stripping was narrow enough to not interfere in the operation of my pressure switch, but resilient enough to push the top and bottom apart as soon as there is no longer any weight on the box.
I then stripped the free ends of the wires I had previously soldered to the alarm, and taped the bare ends to the foil inside the box with aluminum tape, one on the top, one on the bottom. At this point, if you switch your alarm on and push your box together, you should hear a non-too-pleasing screech from the device. You are ready to deploy it to scare away things that go psssst in the night.
Step 4: The Finish & Options
For around $2 total, and less than ten minutes time, one of my favorite creations - because it is simple, practical, cheap & effective.
This switch could easily be adapted to other uses:
It could trigger a doorbell or a camera
It could trigger a multitude of scary devices for Halloween (light up a pumpkin, make creaky noises, drop a hairy spider on their head....)
It could trigger many pleasant things for Christmas (play a medley of carols, drop some mistletoe, have a Santa that "Ho, Ho, Hos"
It could trigger a recording of big dogs barking, making burglars & solicitors both think twice :-)