On Jan 22, 2008 7:23 PM, John T. Blair <jblair1948@cox.net> wrote:
> At 06:00 PM 1/22/2008 -0600, Bob Nogueira wrote:
>
> >Recently it started reversing just before it reaches full close.
> >The "obstacle in the way reversing" is activated by one what looks
> >like a Hall effect sensor you would find in a car, a cup which turns
> >inside the head that has windows which turn with the drive shaft.
>
> Bob,
>
> I thought most obstical sensors were photoelectric beams. An LED either
> visable or IR would emit a light beam to a photo receiver. If the receiver
> does not get the light it opens the circuit so the opener doesn't work or
> reverses.
>
> I don't understand how/why they'd use a Hall effect sensor. Unless they
> are counting time between pulses. If the time is too long, it figures
> that something is stopping or slowing the opener (while it's closing) and
> it stops and reverses.
Garage door openers have two (some have more, these days) safety
system. One is the optical beam sensor. The other is force limiting.
If the door hits something, it's supposed to stop and reverse to full
open. The test for a door is to put a 2X flat on the floor, 2 inch
edge vertical. The door should hit it, and reverse. If it stays
shut, you need to adjust the sensor. On the units I've ever dealt
with, the control for that is a screw on the motor unit. They do
drift sometimes. The other thing that happens is that the chain gets
harder to move, and the amount of force needed to operate the door
goes up. You lubricated the chain lately? or has it been very cold?
--
David Scheidt
dmscheidt@gmail.com
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