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SPDT remote controlled switch?

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?

Reply to
RickH
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I use two PLC modules (X10 Appliance modules or "Universal" modules?) to control two double throw or single throw relays. One relay switches power ON and OFF and the other relay selects the motor or motor winding (drape direction). Even if both relays energize, only one motor (or motor winding) will be powered. The problem is, you will need some logic control to determine which direction the drapes should be energized in.

Reply to
D&SW

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.

Reply to
B Fuhrmann

Thanks to both responders,

This is exactly the situation, I think I'll look for a pulse-toggled latching relay for the motor selection side and a momentary or simple on/off relay for the power. The purpose of the center-off is to stop the drapes at mid position. The drapery track already has micro switches that turn off the appropate motor at the outer and inner limits based on cord position (as the pull cords age and stretch these switches are easily repositioned).

The PLC market seems to have some big holes in basic switching offerings, they go right from SPST to devices with all kinds of bells and whistles, before they've created a basic set of foundation products for switching. A while back I needed a momentary contact PLC switch and could not find that either. I'd like to one day also get a DPDT switch but dont suppose that will be easy either.

Basic switches (other than SPST) sound like a product opportunity for someone wanting to license Insteon in their products (hint hint).

Reply to
RickH

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