RV 12 volt lighting questions

Thread Starter

DouglasPHill

Joined Feb 28, 2021
3
I am just beginning a conversion of a school bus to an RV. (well just beginning the electrical part)
As far as the recessed lighting, the plan is 3 or 4 circuits of 3 lcd lights each. I would like to control
all circuits with a set of 3 way switches, one at the front of the bus and the other by the bed in the back.

From this mornings research it looks like I need multi-pole switches, and in my case multi-pole 3 way switches.
Good idea? Bad idea? that type of switch doesn't exist? Is there a better way to do what I want?

Thank you for all suggestions. - Doug
 

Yaakov

Joined Jan 27, 2019
2,341
Generally speaking, 3-way lighting circuits are very simple. You could use standard 120V switches designed for 3-way wiring and do it in the conventional way. Alternatively, you could do something with a product like the Shelly 1 smart switch box which allows control over WiFi as well as with mechanical switches. Will you have a WiFi network?

Conventional 3-way switching requires only a SPDT (Single Pole Double Throw) switch and 3 wires between the two ends.
 

Thread Starter

DouglasPHill

Joined Feb 28, 2021
3
Generally speaking, 3-way lighting circuits are very simple. You could use standard 120V switches designed for 3-way wiring and do it in the conventional way. Alternatively, you could do something with a product like the Shelly 1 smart switch box which allows control over WiFi as well as with mechanical switches. Will you have a WiFi network?

Conventional 3-way switching requires only a SPDT (Single Pole Double Throw) switch and 3 wires between the two ends.
Thanks Yaakov, Yes planning on wifi, also my post wasn't clear, I would like to use one set of 3way switches to control all 4 circuits.
 

Yaakov

Joined Jan 27, 2019
2,341
If you don’t find it to be overly complex, I would suggest investigate the Shelly 1 devices and something like Node Red which could be the basis for all sorts of nice automation and control. The Shelly 1 has two be advantages: it can be powered by 12V, and it provides a very flexible facility to connect a switch as an additional control.

As far as the conventional route, the switches stay the same, they simply control the supply to the lights so wiring them in parallel on the switch leg of the 3-way circuit doesn’t change the switch requirements.
 

Yaakov

Joined Jan 27, 2019
2,341
Re-reading your original post I see you mention “3 or 4 circuits”, if that’s because of current requirements, I would still do a conventional SPDT switch and use relays to operate the different circuits. There’s no reason to complicate the switch which adds a lot of wiring.
 

LesJones

Joined Jan 8, 2017
3,065
The normal way to do what you want would be to use a SPDT switch at each end. Are you saying that you are trying to find a single switch assembly with 4 switches in the same unit ? If I was doing something that I would consider runing the power cable close to each group of lights and doing the actual switching using a relay of mosfet close to each group of lights. You could then use some thin multi core cable (Such as alarm cable.) between the switches and the switching unit for each lighting group. If you included an XOR gate in each switching unit you could even do what you want using SPST switches.

Les.
 

Thread Starter

DouglasPHill

Joined Feb 28, 2021
3
LesJones and Yaakov, thank you so much for the info. Just talked to daughter and she said she doesn't mind 3 separate circuits, without 3 way switches, front of cabin lights, middle, and back. But, she wonders if there could be a panic button that would turn on all lights. ty
 

Yaakov

Joined Jan 27, 2019
2,341
LesJones and Yaakov, thank you so much for the info. Just talked to daughter and she said she doesn't mind 3 separate circuits, without 3 way switches, front of cabin lights, middle, and back. But, she wonders if there could be a panic button that would turn on all lights. ty
I would suggest the following:

A conventional 3-way switching circuit using SPDT switches, a "hot side", a "switch leg", and "travelers" which provides power to 12V relays connected to as many light circuits as you need.

When the 3-way circuit is on, the relays are energized and provide power to the lights. This is simple, reliable, and cheap.

If you want to control them separately, you can put three switches to actuate the relays, one for each, and a single switch (could be the 3-way, above) that powers them all. In this case you could turn on and off each circuit AS LONG AS THE "MASTER" was off. One the master (3-way) was on, the single switches would have no effect until it was turned off, then it would revert to the state of the switches.

This is why I really like the home automation route. It's more complex but it's completely flexible.
 

LesJones

Joined Jan 8, 2017
3,065
You could have the master switch to actuate the relay via three diodes (Or 4 if there were 4 groups. the master switch would only need to be a SPST switch. You could also have a number of master switches connected in parallel so all the lights could be turned on from a number of different points on the bus,

Les.
 
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