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IR Motion sensors - Tripped by red laser?

pseudolobster

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I work in a secure facility, and in order to get by certain doors you need to swipe your ID badge... to *leave* by these doors though, a motion sensor on the other side of the door will trip and it will unlock without you having to swipe...

I decided to point my 200mW red laser at one to see what would happen, and sure enough it tripped the thing and let me through without swiping my badge... which, of course, I thought was the single most amusing thing in the world... but it got me thinking... these motion sensors don't trip if you're really bundled up in clothes that match the room temperature, so I've always guessed they're run-of-the-mill IR motion sensors, which use a ccd camera of some sort to measure temperature changes in its field of vision.

I can't figure out how a red laser is setting it off, unless it's heating up part of the sensor and the change in temperature is what's tripping it...

Any thoughts?
 

Murudai

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That's funny, so easy to hack into secure facilities.

Though, in places where I use my swipe card to access buildings there is a swipe card thingy on either side. So, no use for me :(
 

MarioMaster

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IR motion sensors usually operate in the very deep IR spectrum (heat) so unless you use your laser to start something on fire in front of the sensor i don't think it would work ;D
 

pseudolobster

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MarioMaster said:
IR motion sensors usually operate in the very deep IR spectrum (heat) so unless you use your laser to start something on fire in front of the sensor i don't think it would work ;D
That was my theory too... which was totally shot to hell by the fact that it *does* work.
 

Murudai

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How about those sliding doors at say, supermarkets? Do those use IR sensors? Maybe someone should try pointing their laser at them!

(I ain't trying it, being in Australia and all... I want to keep my lasers!)
 

Switch

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Murudai said:
How about those sliding doors at say, supermarkets? Do those use IR sensors? Maybe someone should try pointing their laser at them!

(I ain't trying it, being in Australia and all... I want to keep my lasers!)
That was the first thing I thought too.....UNFORTUNATELY they use radar :'( :'( :'( I saw that if you used a low powered laser on the motion sensors it keeps them from setting off.I don't know why that works either.But it would've been hilarious to set your NIR laser on a tripod across the street fixed on the door sensor so it would jam :D too bad....

Btw, what kind of heat sensor do those have? I'm guessing it's not a microbolometer so I can mod them into a thermal imaging camera :-/
 

diachi

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It may be an IR laser with a sensor, and the sensor will pick up red and near IR laser light ?
 

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Diachi said:
It may be an IR laser with a sensor, and the sensor will pick up red and near IR laser light ?
No dude, they detect deep IR.8 to 14um probably.I guess whatever sensor it is just senses a change in heat.Maybe a low res microbolometer kinda like an optical mouse ccd camera? :-/
 

diachi

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Now I'm confused ;D There is a counter in the library near my house that gets triggered when you walk past it, I wonder what that uses :-? It has a reflector across from it :-? I'll need to buy a cheap red pointer and see what effect it has on it .

Diachi
 

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Use the green on it! ;D But be careful for cameras. :-/
 




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