Re: Garage door opener sensors - how do they work?

From: EL (nospam_at_here.com)
Date: 06/08/04 

Date: Tue, 8 Jun 2004 13:16:09 -0400

Bob,

Thanks for the info but I've actually checked that already!

The "force sensor" isn't actually a force sensor at all, rather it detects changes in the motor's RPM (there's a photointerrupter
sensor on the motor shaft) and senses the load that way. Therefore to measure force, the motor must be turning. In the case of
my unit, it doesn't activate the motor at all - it immediately goes to "flashing lights" mode as soon as you press the button.

Eric

"Bob Shuman" <reshuman@removethis.lucent.com> wrote in message news:ca4r0r$g01@netnews.proxy.lucent.com...
> In addition to the photo sensor, there are also usually two "sensitivity"
> limit adjustments for maximum force to both open and close the door. Check
> your owners manual and learn which of these controls the down force limit.
> You should verify that the door springs, rollers, etc. are all operating as
> designed and there is no binding or a mechanical problem. You can do this
> by removing the door emergency release latch and operating the door normally
> by hand. It should go down and up fairly easily and stop at around mid-door
> on its own if the springs are calibrated properly. If this all looks OK,
> re-engage the eclectic opener on the door and experiment with increasing the
> down limit sensitivity to see if this is the problem.
>
> Based on the photo detector lights being illuminated, I'd suspect the door
> close force limit is the problem and it might be as simple as greasing the
> drive and track to reduce the friction and get it back to where the limit
> was previously set. (This is set for safety just in case something or
> someone is under the door while it is closing.)
>
> Good luck!
>
> Bob
>
> "EL" <nospam@here.com> wrote in message
> news:40c5ea48$0$88717$9a6e19ea@news.newshosting.com...
> > I've got a garage door opener that's about 3 years old, made by
> Chamberlain. Brand name is "Access Master" but they also sell
> > them under a bunch of other names including Sears Craftsman and
> Liftmaster.
> >
> > Symptom is that when you try to close the door, it won't move and the
> overhead light flashes 10 times. Door can be made to close
> > by holding the button down on the hardwired controller.
> >
> > My research indicates that this is caused by the unit not getting an "ok"
> signal from the photo sensors, yet the lights on both
> > sensors are on (steady, not flickering). So I figure it's got to either
> be the sensors or the logic board in the unit.
> >
> > Problem is, to diagnose which it is, I gotta have at least a vague idea
> how the sensors work and I don't. "Transmitter" and
> > "receiver" both connect to the head unit in parallel so I have a hard time
> figuring what signal's going where and how, is it AC or
> > DC, etc.
> >
> > Anyone got any idea how these things work? A schematic would be ideal,
> but any info at all is appreciated.
> >
> > Eric Law
> > Jupiter, FL
> >
> >
>
>

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