Re: SPDT remote controlled switch?

["B Fuhrmann" <b-fuhrmann-usenet@xxxxxxxxxxxxxxxxxxxxxxxxx>]

Your present mechanical switch has three positions, no can do with a single
relay (not a typical one at least).
There are multiple ways to do it but you need two bits worth of information.
With the right wiring, two relays can do that and block out the one (out of
four combinations that you don't want).

I am assuming that the motors are wired with switched hot leads and a common
return.

The easiest to wire is one spdt relay that is wired like your switch for
direction and another that you only need a normally open (NO) contact on for
on/off that you wire in series with the direction control.
The two output bits become open/close and on/off and your motors can never
both be activated at the same time.

You can also do it with the two bits being off/open and off/close which is
the version that you are worried about triggering both open and close at the
same time.  You can do this with same two relays.
Relay one is off/open  power to common, NO to open motor, and NC to the
common of the off/close relay.
The NO contact of the off/close relay goes to the close motor.
If you energise both relays at the same time, the open relay connects to the
open motor and the close relay is disconnected from the power.

You have your choice of control styles.  Which one you use can depend on the
logic of your control system or your whim.

--
Bill Fuhrmann


"RickH" wrote ...
> Is there a SPDT PLC switch available?  One that will absolutely
> guarantee that both "throws" cannot become energized simultaneously.
> I have drapes that have separate forward/reverse motors, currently
> there is a simple hard-wired SPDT switch on the wall for open/off/
> close, "Open" energizes the forward motor and "Close" energizes the
> reverse motor.  Obviously energizing both motors simultaneously would
> quickly destroy the motors and the drapery pulls.  So I need a PLC
> switch with a true SPDT relay and 3 programmable "positions", IOW I
> dont want to cobble togeter 2 SPST switches and risk having both
> motors get energized simultaneously due to a communication glitch.
>
> How can I convert this arrangement to PLC so I can have a remote
> controlled drape?
>