PIR misbehaviour?
Hi,
I'm currently developing a system using the PIR sensor 555 28027.
Lately I've found a strange behaviour of my sensor which I cannot explain and I would be very grateful if you could give me your opinion about it.
The PIR has been first tested in a very simple way: Connected to a 3.6V power supply, grounded and its signal output seen on an oscilloscope. Being this devices the only things present in a 2m x 3.5m x 4m room, windowless, without presence of heaters, A/C or any possible IR obvious source I could imagine. After the 10-60 sec warming up time of the PIR in a absolutely absence of people in the testing room, my output signal remains low as expected...but after a while, still in absolute absence of people or in my opinion a any IR source, my oscilloscope shows from 1 to 6 pulses as if some movement was detected...and then, randomly it will do it again. This fact ruins the measure because I'm not able to tell if really some movement was detected or if the signal was triggered by this misbehaviour.
I'll really appreciate your opinion.
Thanks.
I'm currently developing a system using the PIR sensor 555 28027.
Lately I've found a strange behaviour of my sensor which I cannot explain and I would be very grateful if you could give me your opinion about it.
The PIR has been first tested in a very simple way: Connected to a 3.6V power supply, grounded and its signal output seen on an oscilloscope. Being this devices the only things present in a 2m x 3.5m x 4m room, windowless, without presence of heaters, A/C or any possible IR obvious source I could imagine. After the 10-60 sec warming up time of the PIR in a absolutely absence of people in the testing room, my output signal remains low as expected...but after a while, still in absolute absence of people or in my opinion a any IR source, my oscilloscope shows from 1 to 6 pulses as if some movement was detected...and then, randomly it will do it again. This fact ruins the measure because I'm not able to tell if really some movement was detected or if the signal was triggered by this misbehaviour.
I'll really appreciate your opinion.
Thanks.
Comments
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- Stephen
Same test was held today with 2 different PIR: same result and false triggers are not sync. These False triggers produce, when the jumper is set on H, a High level from 2,5s to 4s what becomes not negligible compared with the output produced by the movement of a hand as it was an "impulsive input" (time of the output 3-4 seconds on high level).
@Franklin
Measures with a spectometer were held to analyze the EM spectrum behaviour with no relevant detections, so I guess people from another dimension are not my problem here. (!) Anyway I'd like to ask you why do you think providing the 100k resistor could solve the problem? What do you think the problem is about, that can be solved adding this resistor? Tomorrow I'll try it and I'll tell you if it worked, but I'd really appreciate if you could provide me the idea behind the solution.
Once again, Thanks for your comments, opinion and support.
Andresdrk
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- Stephen
But absolutely zero problems when running at 5v.
I thought I was the only one having false triggering difficulties, until now.
Currently to work around the problem, I test each sensor for a few days at 3.3v before using it.
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