I have an already existing circuit between the mains wall supply and a window shutter (see image), it has a gewiss rocker switch for opening and closing the shutter when you press and hold one of the two-buttons. I want to add another switch that will be operated remotely/automatically. I plan to add this using the pink wiring on the diagram below.

My question is: is this a legitimate circuit? In terms of, what happens if both switches are closed at the same time #1 for alternate directions, and #2 for the same direction (say UP)? Or any other faults you can see?

two relay circuit

  • \$\begingroup\$ What is a "gewiss switch"? If it's a brand name or model then surely it should be capitalised. \$\endgroup\$ – Transistor Dec 28 '18 at 21:37
  • \$\begingroup\$ sorry I was just trying to be specific titansolutionsgroup.co.uk/products/… \$\endgroup\$ – Blundell Dec 28 '18 at 21:38
  • \$\begingroup\$ It is likely important that UP and DOWN are never simultaneously energised, so you should use break before make NC/NO relays. You can have the NO contacts just as you have shown, but you should use the NC contacts to break the opposite circuit. This will ensure the relays cannot contradict eachother or the buttons. \$\endgroup\$ – K H Dec 29 '18 at 2:02

I would use two SPDT relays inserted after the existing switch, like so:


simulate this circuit – Schematic created using CircuitLab

Hmmm - that takes care of conflicts between switch and remote commands, but might need something to prevent a conflict if both relays are operated at the same time.


simulate this circuit

Now, when RLY3 is operated, it removes power from RLY2's contacts - so a remote "Up" command will over-ride a remote "Down" command.

That still has a possible conflict between a local "Down" and remote "Up" commands, but I can't think of an easy cure at present - no doubt someone else will have a better solution.

  • \$\begingroup\$ good idea, so that would mean the remote would have preference if it was wanting to control it. I am wondering about the "conflicts", i'm fine if the circuit doesn't work - but I don't want anything to explode or trip the building. What would a conflict look like? \$\endgroup\$ – Blundell Dec 28 '18 at 22:17
  • \$\begingroup\$ If you operate both relays at the same time, you would send both "Up" and "Down" power to the motor - this might be Not Good. If whatever controls the relays will prevent this - no problem. I'll add another drawing to fix this. \$\endgroup\$ – Peter Bennett Dec 28 '18 at 22:23

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.