Property Instrusion

My father in law has had problems with vandals destroying holiday decorations in his front yard. He wants my help with setting up some sort of intrusion detection system. Something that would sound an alarm to scare away vandals when if they cross onto his property. We thought about putting up a few of those infrared beams.

He'd need to get two sets of these - one to go across the front of the yard and another one across the side of the yard. The rest of the property is proteced with fences. How would I interface these with a siren? Do you guys have any other ideas of how to protect the property? Thanks!
assuming weather permits, hook up a couple of sprinklers, and activate them when motion is detected.
Good idea E. Assuming those IR beams have normally open contacts you could activate a siren driven with a DC wall wart. Something like the "Moose" sirens (Worthington's Catalog #MPMPI-11, $14). They can be driven with 8-15 volts DC so you can use any wall wart you have laying around providing it can handle the current. It's also very loud (rated at 115 dB).

A couple of things to watch is the current capability of both the IR beam output contacts and of course the wall wart as already mentioned.

If the IR beams have normally closed contacts you would have to activate a separate double throw relay. Show us a link to the IR beams you are thinking about and we'll help you out. ;)
Here's a link - Hopng you guys can tell me how to wire everything. I'm handy, but not an electronics guru. Diagrams would be great if possible.

e: Sprinklers might be good, but not to defend the Christmas decorations during Chicago winter. Thanks! Looking forward to more responses.
Oh yeah... About the siren... How do I control how long it stays on? If the person breaks the beam for only 1/2 second, would the siren only stay on for that long? Would I need to install some type of timer to go longer?
Yea, there are a ton of ways to do this. An ELK Timer-Delay unit comes to mind. Maybe supply some concrete specifications and a price range you want to spend. Is AC power available also?
The setup needs to be weatherproof (Chicago climate). Attached is a sketch of the yard. The idea is to set off some sort of alarm when someone enters the property - to scare them away. The area that wouyld be protected by the beams are the dotted red lines. He'd want to be able to turn the "system" off during the day and on at bedtime. The distance from tree to tree is about 25 feet.

Price...??? Cheaper is better. Around $200 (or less) would be good. Do-able? I realize that the beams I posted a link to are nearly that much by themselves. They are first ones I found. Maybe there's something else out there for less. I'm not even sure if IR beams are the solution, since they only trip when someone passes through and not continuously when someone's "inside". Perhaps motion senosors attached to the trees are a better solution. Any thoughts?

<edit>Oh yeah... AC power. I don't think there is currently any in the area. If necessary, he could probably run an outlet into the yard. But, whatever is easier is better.</edit>


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You could put up a fake camera, and make sure the camera is noticeable. I vaguely recall seeing them for $20-$30, might be a good first attempt.

Found it: Here is one:

No one wants to be caught on camera... if they see this it might solve your problem. A cheap first attempt if nothing else.
Too bad an automatic sprinkler is out. If you set up something that makes a bunch of noise, the kids might even get a kick out of setting it off--"ding dong ditch" on steroids.

Wouldn't it be better to use outside motion sensors and ring a chime in the house? Then add a few inconspicuous, 500 watt floodlights. When the chime rings, you wonder over to a window and turn night into day....
IMO I would have the motion sensors / beams set off floodlights too. You make a good point that the kids might like to set off the alarm. There's less fun in setting off lights.

If I wanted the beam (link above) to turn on floodlights, what would I need? How about if I wanted it to send an X10 command?
THIS schematic shows how to wire up the IR unit with a power flash to send an X-10 signal through the power lines. Use the "7279" option which is the Elk Timer Delay Relay unit so you can set the on time from one second to one hour. You will also need a lamp module to turn on the lights.

Just use plastic zip lock bags and tape to weather proof the modules.

Any fellow Cocooners see anything wrong with this setup (I'm a little tired right now and may not be thinking this through clearly ;) )???

Hey, you can also use this to send an X-10 signal to a chime or lamp inside the home so you know when this is happening and can shoot the little bastards that are wrecking your decorations (or would that ruin the Christmas spirit?) :eek:
The easiest way to protect both areas and to be notified of intrusion is to use a driveway monitoring system. They are made for the outdoors, usually transmit wirelessly back to the receiver, and you can get a receiver that allows X-10 components to be attached so you can use a siren or lights. There are many on the market and the price should be in the range of what you want.
Could I use a set of those IR beams from a garage door? Seems like they'd be a lot cheaper than those Optex ones. Maybe they're not meant for outdoor use? Any other reason not to?
If you don't already have a WGL wireless receiver on-site, I'd be tempted to add a TM751 receiver to the center of the yard and use two eagle-eye motion sensors on the trees. Put a bit of black tape over the LED so they aren't obvious when they trigger an indoor chime. If you turn the floodlights on manually (by remote, from inside the house, of course) then you can avoid false environmental triggers turning the lights on and off throughout the night.

I don't know how effective the Rex10 option would be. A loud but invisible dog in a wide-open yard would probably just get the neighbors mad at you.