3 way circuit for 2 switches to 1 led light (12 volt system)

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iverunamok

Joined Dec 31, 2020
2
I've got 2 Ulincos touch switches with 4 wires each... 2 for device(pos & neg) 2 for power source(pos & neg)I have 2 wires coming from the fuse box(pos and neg), and 2 wires from the light

I need to make sure I can turn on/off the light from both switches. HELP?

Thanks!Photo on 12-31-20 at 5.08 PM.jpgLIGHT.jpg
 

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Tonyr1084

Joined Sep 24, 2015
6,088
For a "3 way" switch arrangement one switch needs to be able to countermand the position of the other switch.

Typical 3 way:
1609517428500.png
At best, your switches - - - the first can provide power to the second, but if the second is off then the first can not turn the LED on. And if the first is off, the second one, at best, can turn the light on and off, but that depends on whether it's independently wired to the power source. You may have to add a couple relays to your project because that's the only way I can see it working.
 

sghioto

Joined Dec 31, 2017
2,373
It can be done using two relays as Tonyr1084 mentioned above or if you have the skills a microprocessor circuit.
Relay version:
The outputs from the touch switches are controlling relays which control the LED lamp.
EEE 3 way switch using relays.png
 
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MisterBill2

Joined Jan 23, 2018
9,038
Unfoortunately in the photo the fingers totally hide the useful information. There is no simple way for those devices to pprovide a 3 way switching function. The circuit shown will provide the desired function but it is neither simpleor cheap.
 

sghioto

Joined Dec 31, 2017
2,373
I would disagree. A couple of relays wouldn't cost much and that's about as simple as you can get electrically.
The only issue is the wiring required.
 

Tonyr1084

Joined Sep 24, 2015
6,088
Don't know for sure if this will work, but if you power the bulb from both switches, one switch to each leg of the light then the bulb, seeing 12V on both legs WILL NOT LIGHT. Changing the state of either switch WILL LIGHT the light. If both switches, and here's the part I don't know, if Device + becomes grounded when they are switched OFF then the bulb won't light. But it all hinges on whether the Device + goes positive (on) and negative (off). IF it works that way then yes, this will work. When 12 volts is present on both legs of the bulb there is no current flow, and the bulb remains off. If either of those legs goes to ground (negative) then there will be a current flow and the bulb will light. And if both legs are at ground then the bulb won't light. But ONLY if the switch functions this way.

Now, here's the caveat; if you're trying to power an LED bulb then this arrangement won't work. Not unless you put a full wave rectifier on the bulb. That way, no matter which way the current is going it is properly steered between the two leads of the bulb.
1609558220460.png
It's also possible the black and green wires are common inside the switch. Check for continuity between them with the switch in each position. You MIGHT just get lucky. If that's the case then you won't need to connect the green wire to anything. But ONLY if that's the case. I don't have the switch in hand to test so I can't say for sure.
 

sghioto

Joined Dec 31, 2017
2,373
One thing I noticed is the TS didn't mention what type of switch. There is a momentary, latching and latching with dimming. From the photo it appears to be a dimming type.
I can see the words stepless dimming through the paper at the top.
This will only work with my circuit if you don't use the dimmer function.
Probaby back to the drawing board.
 

MisterBill2

Joined Jan 23, 2018
9,038
I would disagree. A couple of relays wouldn't cost much and that's about as simple as you can get electrically.
The only issue is the wiring required.
If you look at the price, in an auto parts store, of the relays as shown in the drawing, they are over $10 USD each. Yes, there may be less expensive relays available but they are not packaged very conveniently for safe use in a car.
 

sghioto

Joined Dec 31, 2017
2,373
Yes, there may be less expensive relays available but they are not packaged very conveniently for safe use in a car.
That's assuming it will be installed in a vehicle. Either way I would suggest a pre-assembled relay module similar to the photo.
8 bucks on Amazon.
1609607760020.png
 
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sghioto

Joined Dec 31, 2017
2,373
This is the product in question, it just has a single switched output..
Yes we know that, it's the whole purpose of the original post and I'm pretty sure the TS's model includes dimming.
Now to get more involved here's my proposal to wire both touch switches keeping the dimming function.
This requires only one relay but two SPDT switches to complete.
EEE Ulincos 3 way with dimming.png
 

MisterBill2

Joined Jan 23, 2018
9,038
Including two mechanical switches rather defeats the purpose of including two touch switches.

That module shown in post #9 appears that it would work. I do presume that it is for a vehicle because of the 12 volt battery. I think it was a reasonable guess.
 

sghioto

Joined Dec 31, 2017
2,373
including two mechanical switches rather defeats the purpose of including two touch switches.
So does two touch switches. If you simply want to turn the lamp on or off from two locations use a couple of SPDT switches.
I only posted those schematics if the TS prefers or insist on using those particular touch switches. If that's the case then relays and switches are required.
 

Thread Starter

iverunamok

Joined Dec 31, 2020
2
WOW... new to this forum and I logged back on thinking it would take a couple of days for anyone to answer this post... Ya'll are AWESOME! Thank you sghioto, Tonyr1084, Dodgydave and MisterBill2 for your quality ideas and time spent on this puzzle.

I am in the middle of a van conversion, doing all my own electrics(software programer by trade) but this is my first crack at LIVE circuits

When posting, I was at the crux of the light switch board and terribly frustrated because I had researched the 3 way, but when I got the switches, the wiring was a different configuration than expected(4 wires) and most stuff on youtube is AC(which doesn't translate so well to my beginner understandings).

We ran into an issue that day with the build where we had to move faster than expected on getting the wall closed up, so I decided to save myself the headache and just use the switch I had planned for the 2nd switch to break up the lower and upper cabinet lighting instead.

To answer your questions, the reason I wanted these dimmable switches was for an entry light switch by the sliding door of the van to light up a dimmable LED by the entrance... and then the whole switch panel is able to be be accessed while in bed as well. The reason for the product itself was because of esthetics and expectations of a future renter of the van understanding what switches are what without labels. Also they were already installed in the wall. All rookie stuff ha

If doing it in the future I would likely try sghioto's solve... but again if wanting to keep it dimmable, so much research would have to have been involved. Maybe if I ever do a remodel of the van, I will try again!

Now I have the whole 4 feet of distance to have to move around in... not the biggest hurdle :)

Thanks again guys
 

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