Wireless Door Alarms Protect Your Stuff From Afar


[Webby] had a friend named [Steve], and as the story goes [Steve] had a few storage sheds on his property that were prone to break-ins.

While the doors were all fitted with a lock, wooden doors are only so strong, and are easy fodder for intruders bearing crowbars and the like. [Steve] was looking for a good way to know when people were poking their heads where they don’t belong, so he rigged up a set of simple alarms that let him know when it’s time to break out the shotgun.

On each of the shed doors, he installed a small IR proximity sensor wired up to a PIC12F675 microcontroller. The PIC is is connected to the “call” button a medium range wireless radio, so that whenever the IR sensor detects that the door is ajar, the PIC triggers an alert on the base unit.

The solution is simple, which we figure also makes it pretty reliable – nice job!

20 thoughts on “Wireless Door Alarms Protect Your Stuff From Afar

  1. Um yeah, that’s a fail install. dont mount anything to the door because once good hard kick and the radio goes flying and all the wires rip out.

    Plus if he has power out there, (cant be batteries unless he runs around replacing them daily) why not just install a regular OTS alarm with a loud as hell siren.

  2. First if the radio only signals when door is open the batteries never get wasted i assume.

    Second… im sure the PIC Micro is faster than the falling of the radio. If it gets hit hard enough it will surely trigger the IR sensor which would then trigger the radio in about 100ms im sure so falling and messing up will happen only after the signal is sent.

    Now while this is cool… if i was the guy and got away once ill know not to go through the door and simply pry open a new spot on the wall. Since its all wooden and stuff.

    Also piece of aluminum across the radio to secure it more would be a good idea just

    1. Exactly. Use a reed switch attached to the power and mounted on the door and frame, then solder the talk key so it is always pressed. That way, this could run for years all while being completely portable and without having to worry about battery changes. This project is way too complicated for what is trying to be achieved.

    2. If this guy has the land for sheds and such, chances are gunshots will not be reported much…. So, following your idea; put the PIC on the house side controlling a servo, connected to a (shot)gun full of ‘blanks’.

      door_open == gunshots

  3. If you follow the link to the more detailed description, you see that the unit is connected to IR proximity sensors on the outside, so it ought to detect the suspicious person and sound the alarm when the guy’s just standing out near the door. It’s not detecting intrusion, it’s detecting someone while they’re still outside the door. Probably also detects deer and other wildlife.

    Other people may want to change things if they implement it, but I say kudos for hacking this together with what was at hand, and thanks for sharing it and giving ideas.

    Also, to pick up on what others have suggested, I’d never ever risk building a booby trap with lethal force. But a bucket of paint, dye, or some harmless but very foul smelling concoction might make it easier for the police to track who it was who had entered the shed.

    1. FCC rules are meant so people can share the band.

      this project transmits for 1 minute once every 6 months (if that) and most likely at 3am, noone will care, not even the FCC, unless your trying to sell it…


      you can do WHATEVER you like with radios, long as there is no power! (tx sw)

      its like punching the guy holding a gun to your head, you may get sued for assault (in my country), but you get to keep your life and everything you own. also, suing you is admiting he was THE guy with the gun :P

  4. In California, sliding door entryways to pools are required to have an extremely loud alarm to prevent children from drowning. My parents needed to have one installed to pass inspection for renovations. It seems like an easier better option because the thief would hear the extremely loud alarm, and it would be audible from the house.

    I think this is the one they used: http://amzn.com/B003UVZG32

  5. aside from all the suggestions, some of which i agreen on,

    execelent hack! it shows the true meaning of “use these things i already own or can get cheap”!

    lol i think the sentry gun with blanks would be perfect!

    == if i tried to steal and alarm went off, then next time find out why and disarm or go around it.

    also alarm means contents of shed are worth protecting/stealing.

    == if the first time i tried stealing i was “shot at” by “someone” from a dark corner, i wouldnt come back! EVER!

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