What can be used to stop back flow of current?

HappyHippyDad · Feb 12, 2019

My friend has a garage door that when opens turns on a floodlight.

He know wants it to turn on another light in the garage as well as the floodlight.

The problem is this garage light is already on a plate switch, if the garage light was simply connected to the control panel then the plate switch would then operate the flood light as well, this needs to be avoided. (see pic below)

Does anyone have a simple solution? Is there anyway to allow the line current only to flow from the panel and stop the back flow of current to the panel from the plate switch?

Strima · Feb 12, 2019

Contactor.

telectrix · Feb 12, 2019

use a relay. energise with the plate switch, use 1 piair of contacts N/O to switch gaage light. at same time use a pair of N/C to isolate floodlight from switch.

HappyHippyDad · Feb 12, 2019

Strima said:
Contactor.

I was just about to add, can I use a contactor or relay! However, having just dealt with domestic electrics I am unsure how these work or would be connected into the circuit. If anyone could expand a little that would be great, thanks.

telectrix · Feb 12, 2019

230V coil relay. energise with switch.pick a set of contacts.feed to common, N/Oto garage light, N/C tobreak switch feed to flood.

HappyHippyDad · Feb 12, 2019

I think a diagram may be needed..... RICHARD!!

snowhead · Feb 12, 2019

If the plate switch isn't being used as 2 way you can use that.

Connect the light to Common,
Feed from the control panel to L1
Permanent feed to L2

HappyHippyDad · Feb 12, 2019

snowhead said:
If the plate switch isn't being used as 2 way you can use that.

Connect the light to Common,
Feed from the control panel to L1
Permanent feed to L2

Snowhead! That is so simple yet effective. Many thanks

Ps.. It is being used as 2 way (I was just lazy in my drawing), however he never uses the other switch so I can just eliminate it.

Lucien Nunes · Feb 12, 2019

NOOOOO! Not this again! Is this the same door or another one?
If the light supply and door opener supply are on different circuits you can't do this as it ties the two circuits together. Even if on the same circuit, the door opener cannot be isolated using its means of isolation; the neutral remains connected and the line is disconnected only by a functional switch. You must use a relay.