No guarantee, but if I were designing the circuitry, the lead that
carries power would also serve as the signal -- with nothing
interrupting the beam, current flows; when something interrupts the
beam, the current stops and my control logic watches for current
flow. This also either stops the motor or raises the door if the
wires to the sensors fail.
HTH,
Donald.
> Date: Sun, 23 Mar 2003 17:33:27 -0500
> From: Steven Trovato <trovato@computer.net>
>
> Hi all. Does anyone know how a garage door safety reversing system works,
> from an circuitry perspective? I'm talking about the beam transmitted
> across the opening. There are two screw terminals on the opener for these
> components. The IR transmitter and receiver components each have two
> wires. One from each goes to each screw terminal. One is obviously
> supplying power and the other is obviously a common ground. There is no
> separate "signal" wire to indicate that the beam is obstructed or
> clear. This must be superimposed over the existing two wires
> somehow. Anyone know how? The particular unit in question is a Sears
> (Chamberlain), but I'm sure others are similar. Thanks.
>
> -Steve Trovato
> trovato@computer.net
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