| PipeDown 2005-08-23, 6:21 pm |
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"Percival P. Cassidy" <Nobody@NotMyISP.net> wrote in message
news:N4KOe.87$Yh6.22@fe04.lga...
> Here's one for the electrical/electronics gurus.
>
> Our new Wayne-Dalton iDrive garage door opener operates its associated
> light fitting via an IR beam: the opener proper installs right above the
> door, while the light fitting can be mounted to any convenient outlet
> within "view" of the opener.
>
> The light operated correctly when it was first installed, but then would
> sometimes switch on but not be able to be switched off except by killing
> the power to that circuit -- and even then the light would sometimes
> switch on and stay on as soon as power was restored.
>
> I called Wayne-Dalton Customer Service. The rep. asked whether we had
> fluorescent lights in the garage. I replied that we did but that the
> problem existed even when the fluorescents (CF) were turned off. The rep.
> then said, "We have found that fluorescent lights can interfere with
> infra-red sensors even when the lights are turned off." I told her I
> couldn't see how that could be, but there was no point in arguing, because
> she was only reciting her official spiel.
>
> They are going to send a new light unit and a new motor-control board
> (mine is an older revision, it appears), but . . .
>
> Please tell me that there's no way a switched-off fluorescent can
> interfere with IR circuits.
>
> Perce
Electrically speaking the CF bulb is inert when switched off because it has
no standby mode, it is just off.
But... stretching my imagination, can the IR light from the beam interact
with the phosphors of the bulb and reemit light that interferes? Unlikely
but seems plausable. The phoshhor should absorb UV and emit visible, I
don't know of its performance in the IR band.
Most IR beams are not ON/OFF but have pulses encoded in them so that they
are not easily fooled by passive IR sources.
Try to find the Radio Shack Infrared sensor card (276-1099). It has a patch
of phosphor on it that glows red in the presence of an IR beam. It is
useful to see where the beam goes.
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