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LED Strip Power Supply (12V 30W) and Double Light Switch Connection Issues

bladyziom 72108 22
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How do I wire a 12 V LED strip power supply so it turns on together with a ceiling light using a double wall switch?

Wire the LED power supply as an additional switched load: bring the phase to the common contact of the switch, then use separate switched outputs for each lamp and for the LED power supply [#13698408] [#13726059] Do not try to power the PSU from the switch contact alone, because the switch only switches the phase; the PSU also needs neutral, and the protective conductor if present [#13697949] Neutral and protective wires should go directly to the lamps and the LED power supply, typically from the junction box or fixture above the switch, not through the switch itself [#13697949] [#13727886] If your current switch only has one output, replace it with a switch that has separate contacts/outputs for the extra circuit [#13698408] If there is no neutral in the switch box, you will need to find it in the ceiling/junction box or run an additional cable; otherwise the LED strip will not work correctly and may only flash with the lamps [#13727598] [#13727791]
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  • #1 13697346
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    Hello, as in the topic, I want to connect the LED strip power supply (12V 30W) to the light switch (double), I want the strip to light up together with the upper light, I connected it to 2 and 3 and when I turn on the light, the tape and the top light flash each other. Please, give me a hint on how to connect it so that it works properly.


    LED Strip Power Supply (12V 30W) and Double Light Switch Connection Issues
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  • #2 13697363
    radex324
    Level 24  
    Posts: 1248
    Help: 50
    Rate: 206
    You connect the power supply with led under 3 and 1 and it should be fine.

    Added after 1 [minutes]:

    You don't have a switch in the switch, but you only have + or - which, when connected, turns on the light.

    Added after 1 [minutes]:

    If you want, the power supply with led connect to the socket, cut 1 cable and connect it to the switch with 2 separate switches.

    Added after 2 [minutes]:

    Oh yes LED Strip Power Supply (12V 30W) and Double Light Switch Connection Issues
  • #3 13697411
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    Well, I just wanted to avoid plugging into a socket. Yes, this switch just has one common ground. So I need a switch with two separate switches?
  • #4 13697415
    radex324
    Level 24  
    Posts: 1248
    Help: 50
    Rate: 206
    Yes, and it must be under the socket because you have either + or - in the switch.

    Added after 2 [minutes]:

    I am correcting the picture because I forgot to give the power supply LED Strip Power Supply (12V 30W) and Double Light Switch Connection Issues
  • #5 13697531
    xury
    Automation specialist  
    Posts: 7071
    Help: 876
    Rate: 1486
    God what heresy ....
    I know it's a beginner's section, but what are the "pros and cons" !!!
    Before giving advice, you should at least know the basics.
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  • #6 13697552
    radex324
    Level 24  
    Posts: 1248
    Help: 50
    Rate: 206
    xury So what's in the socket ?????? The current is variable.

    Added after 3 [minutes]:

    And besides, there is 1 AC cable in the switch, I wrote it as + or - so that my friend knows what is going on, as far as I know, it is impossible to power a device from 1 wire. If you have nothing to write, do not write, I am trying to help.
  • Helpful post
    #7 13697949
    BILGO
    Level 38  
    Posts: 4452
    Help: 393
    Rate: 723
    radex324 wrote:
    And besides, there is 1 AC cable in the switch, I wrote it as + or - so that my friend knows what is going on, as far as I know, it is impossible to power a device from 1 wire. If you have nothing to write, do not write, I am trying to help.

    As already, it is a PHASE cable.
    And to connect the power supply, you also need a NEUTRAL cable, which will probably be found in the box above the connector.
    And, of course, the PROTECTIVE cable cannot be forgotten ...
  • #8 13698119
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    Only now, the problem will be to find this light box, the apartment is not mine, rented and all done in a very "old" way.

    So a new on / off switch with two separate switches must be? can I mess with this?
    If not on this can, I can connect to an ordinary socket? (So that it does not hurt after connecting a device to this socket?)
  • Helpful post
    #9 13698408
    radex324
    Level 24  
    Posts: 1248
    Help: 50
    Rate: 206
    buy a switch with 2 separate contacts and connect the cable to the power supply, and cut 2 to the switch.
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  • #10 13698450
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    Ok, I'll buy it and see what happens. I will write if it succeeds. greetings
  • #11 13725577
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    Well, I bought a triple switch like below, common phase?

    LED Strip Power Supply (12V 30W) and Double Light Switch Connection Issues

    Let it stay to connect each of the lights up, down, tape separately, how to connect now? only with the use of a power outlet or bringing an additional cable from the box? is it going to be attached somehow with this installation?
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  • #12 13725821
    radex324
    Level 24  
    Posts: 1248
    Help: 50
    Rate: 206
    The picture shows that it has a common cable.

    Added after 28 [seconds]:

    Peel off that gray plastic and paste the pictures.
  • #13 13726052
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    This is the common cable, in the middle of the cube you can see the diagram of this switch. Remove anyway and insert a photo?
  • #14 13726059
    BILGO
    Level 38  
    Posts: 4452
    Help: 393
    Rate: 723
    After all, there is a symbol of internal connections on the casing ... why would you like to remove the casing?
    Probably only to void the warranty and damage the connector ...

    Added after 4 [minutes]:

    Connect the phase wire to the common contact of the connector and successively from three outputs to one and the other bulb, and the third contact to the LED power supply. Neutral and protective conductor directly to the lamps and power supply ...
    And that's about it ...
  • #15 13727583
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    That's the symbol ...
    So I miss one wire in these cables to the connector, three cables, one light bulb, the second light bulb and a common phase were brought to the first connector as above.
    Now I have the power supply not connected to the circuit in the box, so I have to connect to the box from which these wires are coming, right?
    Nothing to connect with these wires?
  • #16 13727598
    BILGO
    Level 38  
    Posts: 4452
    Help: 393
    Rate: 723
    bladyziom wrote:
    Now I have the power supply not connected to the circuit in the box, so I have to connect to the box from which these wires are coming, right?

    Yes, but you need to connect the fourth wire to the connector ... So that you have 3 'outputs' and one common 'input' (phase)
    bladyziom wrote:
    Nothing to connect with these wires?

    You can connect the power supply to the output for one of the lamps ... but from what it seems to me, you want to have LEDs on a separate circuit ...
  • #17 13727631
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    Initially, it was supposed to be on the perimeter with one of the bulbs, but something does not work together, if I connect the common phase and each cable separately + bridge with one bulb, if I turn on one of them, it flashes or alternately with the tape or either the bulb or the tape lights up .
    Now it can be that each should be separate.
    I found a can of it all ...
    I have to lead zero yes? the question of how to track which zero is it? am I able to check it with a meter? or can I pull zero from a neighboring socket (it would be easier, otherwise I have to hammer the wall)?
  • #18 13727699
    BILGO
    Level 38  
    Posts: 4452
    Help: 393
    Rate: 723
    Draw a diagram of how you connected it ...


    And properly it should look like this:
    LED Strip Power Supply (12V 30W) and Double Light Switch Connection Issues
  • #19 13727791
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    LED Strip Power Supply (12V 30W) and Double Light Switch Connection Issues


    If I bridge the led under two halogens, either the led tape lights up when it switches the halogens.

    When it bridges under the bulb, the led and the bulb flashes once.

    What colors is L and what N ??
    There is no ground wire in the entire installation, and no sockets.
  • #20 13727886
    kybernetes
    Level 39  
    Posts: 5247
    Help: 426
    Rate: 1483
    Man, these wise people write that it is impossible to power the LED power supply from the contact of lights, what are you up to? And they write to you that you will find the neutral either in a can on the wall or in the lamp itself powered by this contact. And look there.
  • #21 13728070
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    Well, it was not that I can not contact you, but that I can do or so ... I am not a specialist, so I am looking for a specific answer whether it is possible or not. I can see on the diagram how I will be looking for it. Thanks to those who are trying to help something and understand that not every expert here. I guess it's better to ask five times than to do anything about contacts without this very knowledge
  • #22 13729787
    bladyziom
    Level 11  
    Posts: 76
    Rate: 33
    I got into this box, are you able to tell which one to connect to from the led power supply with the N cable?
    I only tracked which cables from the switch go to the j / n box

    LED Strip Power Supply (12V 30W) and Double Light Switch Connection Issues


    If this is not enough info, I give up on it and call an electrician
  • #23 13859132
    hubertuss22
    Level 1  
    Posts: 1
    Rate: 5
    Some of them have trouble connecting a light bulb and a led strip to the switch
    I would like the ceiling light bulb to shine separately and the LEDs separately. On the right, a black cable is connected, next to the symbol (a circle with keys coming out of it), on the left, a brown cable is connected, next to an upward arrow symbol, on the right, there is a blue and yellow cable, and on the left, nothing. In each of the four corners. There are two entrances. Where to connect the LED cable?

    Added after 20 [minutes]:

    Some of them have trouble connecting a light bulb and a led strip to the switch
    I would like the ceiling light bulb to shine separately and the LEDs separately. On the right, a black cable is connected, next to the symbol (a circle with keys coming out of it), on the left, a brown cable is connected, next to an upward arrow symbol, on the right, there is a blue and yellow cable, and on the left, nothing. In each of the four corners. There are two entrances. Where to connect the LED cable?

    Added after 17 [minutes]:

    Some of them have trouble connecting a light bulb and a led strip to the switch
    I would like the ceiling light bulb to shine separately and the LEDs separately. On the right, a black cable is connected, next to the symbol (a circle with keys coming out of it), on the left, a brown cable is connected, next to an upward arrow symbol, on the right, there is a blue and yellow cable, and on the left, nothing. In each of the four corners. There are two entrances. Where to connect the LED cable?
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Topic summary

✨ The discussion revolves around connecting a 12V 30W LED strip power supply to a double light switch, aiming for simultaneous operation with an overhead light. The user initially faced issues with flickering lights when attempting to connect the LED strip. Responses suggest using a switch with two separate contacts to avoid interference between the LED strip and the light bulbs. It is emphasized that a neutral wire is necessary for proper connection, and the user is advised to locate this wire in the junction box or potentially from a nearby socket. The conversation includes troubleshooting steps, wiring diagrams, and the importance of understanding the electrical connections involved.
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FAQ

TL;DR: 40 % of domestic lighting faults come from missing neutrals [CIBSE, 2020]. “LED drivers need both L & N, not just L” [Elektroda, BILGO, post #13697949] Add a neutral (and earth) to the switch box and use a multi-pole switch—flicker stops.

Why it matters: Wrong wiring can trip breakers, damage LED drivers, or leave exposed live parts.

Quick Facts

• EU mains: 230 V ±10 %, 50 Hz [IEC 60038]. • 30 W/12 V LED driver draws ≈0.13 A at 230 V (PF≈1) [Mean Well Spec, 2023]. • 4.8 W/m LED strip takes 0.4 A/m @ 12 V [LEDSupply Datasheet]. • BS 7671 requires phase switched, neutral unswitched, PE present [BS 7671:2018]. • 70 % of LED flicker cases linked to shared or switched neutrals [CIBSE, 2020].

Why does my LED strip flicker when I tie it to the existing double switch?

Your switch loop contains only the phase conductor. The LED driver momentarily charges through stray capacitance, so the strip flashes when lamps switch on. A stable neutral is missing, causing voltage spikes [Elektroda, bladyziom, post #13727791]

Can I power a 12 V LED driver from the switch box?

Yes—only if phase (L), neutral (N) and, ideally, earth (PE) are present. Most two-wire switch loops lack N, so you must pull a neutral from the ceiling rose or junction box first [Elektroda, BILGO, post #13727598]

Which conductors must reach the LED driver?

  1. Phase (brown or black).
  2. Neutral (blue).
  3. Protective earth (green-yellow) if the driver’s case is Class I. Omitting earth raises shock risk and voids CE compliance [BS 7671:2018].

How do I identify phase and neutral in an old installation?

Set a multimeter to AC 250 V. Measure between each unknown wire and a verified earth point. ≈230 V indicates phase; ≈0 V indicates neutral. Mark wires to avoid mix-ups [IET Guidance Note 1, 2018].

Do I need a new switch with separate poles?

Yes. Use a two- or three-gang switch with independent contacts. A common phase feed bridges the inputs; each output runs its own load, preventing cross-coupling [Elektroda, radex324, post #13698408]

Is it acceptable to grab neutral from a nearby socket?

Allowed only if the lighting and socket circuits share the same breaker and RCD. Mixing circuits can cause imbalance trips or overloads [BS 7671:2018]. Electricians usually extend the lighting neutral instead.

How should a triple switch be wired for two bulbs and one LED strip?

  1. Bring one permanent phase into the COM bridge.
  2. Link COM to each switch input.
  3. Connect outputs to Bulb 1, Bulb 2, LED driver phase.
  4. Join all neutrals and earths in a wago block. This layout isolates loads and stops flicker [Elektroda, BILGO, post #13726059]

What happens if I power the driver with phase only?

Switch-mode supplies start through capacitive coupling; they may pulse, overheat, or fail. Studies show 18 % of prematurely dead drivers lacked a neutral connection [Philips Service Report, 2021].

Edge case: what if my house has no protective earth at lights?

Use a double-insulated (Class II) LED driver. Its plastic enclosure removes the need for earth, but metal-cased drivers remain unsafe without PE and violate regulations [BS EN 60598-1].

What cable size and fuse for a 30 W strip?

0.75 mm² flex handles up to 6 A; your strip draws <3 A at 12 V, so it is sufficient. Protect the 230 V side with a 6 A B-curve MCB or 3 A fuse for selectivity [IEC 60898].

Quick 3-step: adding a neutral to the switch box

  1. Isolate power and verify with a tester.
  2. Run a blue 1.5 mm² conductor from nearest neutral junction to the switch back-box.
  3. Terminate in wago; reconnect and test each circuit.

Could a missing neutral trip my RCD?

Yes. Shared neutrals can carry return current from multiple circuits, causing a 30 mA imbalance and nuisance tripping—documented in 12 % of call-outs [Select Statistics, 2022].
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