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PIR Sensor Hacking

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SockThief:
G'day Brains Trust

have a new project im thinking about getting around to doing! But Im stuck at the first hurdle, and a few google hits later, with no answer, its off here to see what you guys reckon.

What I need to do is non-destructively hack a PIR sensor to constantly trigger as if motion is detected, without any motion taking place... the sensor is built into a weatherproof camera, hacking into the box to play with the sensor is out, as it will destroy the seal (as I live in Sweden - I need to ensure the best seal against the elements as possible), Im hoping that there is a simple solution to fool the sensor, maybe some al-foil over the sensor, but not sure at the moment.

On the one hand, the sensor wants to detect as much motion as possible, in the sense of a security monitor, but not suffer too many false triggers. In my case, im thinking the camera is not too picky on the false positives, as the worst that will happen is some recording of a pet, so hopefully the tolerance is a little nicer, though I haven't bought the camera yet, as I don't want to spend the cash if it won't do the job, and so I'm not sure yet...

any ideas?

Rerouter:
high intensity IR led pointed at it flashing via a 555 timer, they scan for a change in the IR image rather than specific motion with most of the,,

SockThief:
hrmm now that is an interesting thought.... the PIR sensor im looking at has a rather large FOV and sensing up to 15m, so an IR LED piggy backed on might just do the trick

im mystefied at myself that I didn't think of that...!

SockThief:
With rerouters suggestion at hand, ive done some more googling, and it appears (at least in some models) that IR appearing and then disappearing wont trigger a PIR sensor, however an IR source moving would... could always bounce it off a rotating mirror!

hrmm more thinking required...

muvideo:
Consider also that the IR range of interest for the PIR (5-15um) is far from the usual
IR led range (0.8-1.1u). This could be a problem, you can also try a small incandescent
bulb lamp instead of the led.

Fabio.

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