Is there a threshold detector/infrared beam alarm?

Now that the summer weather has arrived, I like leaving the patio doors open, but I also want to work on the computer upstairs. What I'm looking for is an alarm of some kind that would sound if an intruder crossed the threshold into the house. It would probably have an infrared beam or possibly be ultrasonic. It would need to be portable, e.g. attachment via sucker or clamp, so that it could be removed easily.
Anything like this in the sheds?
MM
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I take it you don't already have an intruder alarm installed then. :-) A web search for Stand Alone PIR detectors might give you a few good hits to follow.
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On Tue, 19 Jul 2005 13:05:07 GMT, "BigWallop"

Yes, I do. How will that help if family members are moving in and out of the kitchen (but not into the garden)? They may be gone for 30 minutes, and then the alarm will sound when they come back. However, in the meantime an *intruder* might cross the threshold. It is he (maybe a she) I want to be warned about.

MM
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Then have a detector installed on the patio door that only detects the small area around the said door. You should be able to set the alarm system to give a chime or internal sounder only on just that detector in part set zones.
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MM wrote:

Natives not friendly by you then? :-)
I would have thought the farthest away from the doors would be best, giving you time to intercept(my thats a nice word)the would be intruder.
A webcam and software is all's thats needed, the software has a function whereby it throws the image up on the PC screen when movement is detected in the field of view and also giving you a pic of the would be intruder.
The software... http://www.webcamxp.com /
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I could not be watching the screen constantly. I might want to read. Plus, if I'm programming I don't want to be continually switching to another monitor to check. A simple alarm from a loud klaxon or bell, and then I can go downstairs and start to parley.
MM
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On 21 Jul,

My motion detector software will set off an awful noise when motion is detected, as well as emailing a picture of the 'burglar' to an outside address, and putting a video on a website. It's very versatile.
--
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You can get stand-alone battery powered PIR alarms which can be set to chime or to sound a full alarm when triggered.
If you have a house alarm with a PIR sensor in that room, it might be able to be programmed to have a chime function which you can enable/disable when required. (I do this with a Comfort alarm system, in slightly different circumstances.)
--
Andrew Gabriel

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On 19 Jul 2005 13:17:02 GMT, snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote:

My alarm system has a movement detector in the kitchen, but it will not distinguish between legal and illegal movement. I don't want to be continually remembering to disable the alarm when I'm downstairs, then renabling it when I disappear back up to my computer room. In this very hot weather I open the french windows at 8 am and close them at 10 pm, then trust to luck. The likelihood that anyone in this remote part of Britain will come wandering in is quite low, but that's probably what the Clutter family thought, too.
MM
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On Tue, 19 Jul 2005 14:01:39 +0100, MM wrote:

Not that I have noticed, Tandy used to have a box that did what youw ant. Try googling on "break beam alarm"?
--
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Dave Liquorice wrote:

If a PIR detector is acceptable, Lidl will have them in from Monday, 3.99
3 - Infrared movement sensor with krypton light bulb (15 hours burn time). Light and acoustic alarm activated when motion detected. 60 angle of detection within a range of 6 metres. Requires 4 x UM 2 batteries (not included). http://www.lidl.co.uk/gb/index.nsf/pages/c.o.oow.20050725.p.Detectors_Movement_Sensors
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No idea about the sheds, but an electrical wholesaler will probably have something along those lines as a shop door bell.
Colin Bignell
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Not portable, but we have something like that wired in across the drive. Put in by previous owners.
It has beam of some sort. IR I guess, which bounces of reflector and back to the sensor. Breaking the beam sounds a buzzer
--
Chris French


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If you can solder, there's a Vellerman kit from Maplin that looks ideal. IR Beam break detector. It's classified as 1, so the simplest to build.
Both units (TX&RX) take 9 volts so could be battery or wall wart powered.
LL64 - 9.99
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On Tue, 19 Jul 2005 23:48:16 +0100, "Dave Plowman (News)"

Ah, now that's interesting. I ~can~ solder, but I've only ever done it with 'proper' solder. Not sure how I'd get on with the lead-free stuff.
MM
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As far as I know, the old electronic lead multi-core is still available.
--
*I yell because I care

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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