DIY Burglar alarm

68

By scarytaff

DIY Burglar alarm

I came home from the shops on a Saturday morning, a few months back, and my wife greeted me with the words, 'Your workshop has been broken into and everything is gone.' I was gutted! I'd been burgled! It was a bit like closing the stable door after the horse had bolted, but I decided that I'd have to make a DIY Burglar alarm.


Police

I raced down to the bottom of the garden and the door to my lane was hanging on a hinge and my workshop door wide open. All of my tools had been stolen. My bench saw, planer, hand drills, router, polishers, sander, electric saws, tree lopper, chain saw, even my gardening knife. All gone. When the police came they didn't hold out much hope of catching the thieves or of recovering any of the tools because, they said, the thieves would have already fenced them. But they did give me a very loud and piercing 120decibel alarm to fit to the door, and they warned me that the thieves would be back, after I'd bought new tools.


Police alarm

Police alarm
See all 5 photos
Police alarm

Suggestions

Of course my mates down the club had the answers: electrify the door knob: rig up an axe so that when they open the door, the axe chops them up: fit a twelve bore cartridge in the vice so that it fires when the door is opened: lay a pressure mat so when they step on it an arrow is released from a crossbow. All good ideas, if a trifle over the top.

The solution

I settled for the alarm the police had given me and a back-up alarm of my own device. The police alarm fits on the door at the top and a short link from it fits over a hook on the door frame. When the door is opened, the link pulls out a pin and the alarm goes off. All very well, I thought but if the thieves spot the link, they can just unhook it as I do when I enter the workshop. So I built a back-up, DIY burglar alarm, just in case.

First I rigged up a bank of three high wattage spot lights to shine on the door as it's opened, run from the mains power. Then I connected a 12volt car horn to the lights, driven by a mains/12volt transformer. Using a refrigerator's internal switch, the one that brings the fridge light on when you open the door, I connected that to the door frame and ran the cable to the lights/car horn. So that I can get into the workshop without deafening myself, I fitted a switch just inside the door enabling me to open the door a crack and turn it off. When the door is opened by anyone not in the know, the fridge switch pops out and brings on the lights and car horn and the opening door pulls out the link on the police alarm, causing panic and confusion among the baddies.

Hidden switch

The fridge switch
The fridge switch

Result

Well, I'm happy to say that last night the thieves returned, and my DIY Burglar alarm worked a treat. This morning, the alarms were blaring away, the lights shining brilliantly, and nothing had been taken. I just hope their heads are still ringing.

circuitry

Wiring up
Wiring up

Diagram

circuit
circuit
Transformer and Horn
Transformer and Horn

Comments

burglar security 2 years ago

scarytaff,

Wow, what a story! I'm sorry you lost all your tools, I know that a good tool collection can be the work of a lifetime!

But at least it now gives all your friends and relatives a nice and easy gift list for birthdays etc...(gotta find that silver lining!)

It must have been extremely satisfying to thwart their attempts when they came back, it made your page all the more interesting to read, thanks.

scarytaff profile image

scarytaff Hub Author 2 years ago

Thanks for the comments, it's very satisfying knowing that I beat them on their second attempt. Cheers.

Travis Salas 11 months ago

I enjoy my visits as there is always a good read here. Keep up the good work!

scarytaff profile image

scarytaff Hub Author 11 months ago

Thanks for stopping and reading, Travis.

Neil 2 weeks ago

Hello, I am planning on making a home-made alarm for my shed, and this is how I ended up on here! Some good no-nonsense advice - thanks. I like the idea of the fridge switch. I had been looking at magnetic door switches. Neil

scarytaff profile image

scarytaff Hub Author 13 days ago

Good luck, Neil. At least you'll know that if the little so and so's break in, they'll get the scare of their lives.

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