Hi brains trust,

Total Newbie, sorry moderator if posted to wrong forum.

Most RV's install White light and would love a take advantage of using amber lights as well. Amber helps with detracting bugs.

Attached is a schematic that shows how to convert a typical positive/negative 12v single color light into using dual colors if the light has both led's installed.

Question, I don't understand the schematic and would be grateful if someone could explain how to layout the diodes and solder the cables back, lastly, the cabling to the dpdt switch. If anyone is able to show on photos how this works, I'd appreciate the effort because this is over my head.

Products required
1 x DPDT switch
Diodes
and of course the Amber/White light

 

The dashed lines in your schematic represent a component which comes in a package like an IC. I redrew the schematic because you only need 2 diodes and a SPDT switch. Follow the current path from +VE to -VE to understand how it works. Only use OEM automotive parts as lights from China are often illegal and dangerous. The diodes aren't really needed because the switch allows one current path at a time but they do provide extra protection against reverse currents in a fault scenario.

 

You don't need any diodes and use a SPDT switch with the center position OFF.

 

thanks for your help

 

The advantage of using the diode bridge is that it only needs two wires, so you could control multiple light fixtures from one switch without having to pull an extra wire.

 

I don't see the need for a bridge or any diodes in this application. The DPDT switch in the original schematic reverses the polarity of the DC supply requiring the bridge but why?

 

I have an RV that has only two wires embedded into the wall and back to the standard switch, I can't pull another wire through for the amber.

I need a solution to switch from white to amber light without pulling a third wire. I've only got a small amount of room behind the light which would be perfect for diodes due to the size.

 

Does your light fixture have both LEDs installed with a common negative? If so it might be feasible to use the RV chassis as the ground connection eliminating a return wire.

If no chassis ground connection then using two fixtures in this arrangement only requires 2 wires. Which is the original circuit shown in post #1.
The switch reverses the polarity of the voltage applied to the fixture and the diodes steer the current to the appropriate LED. Only drawback is the voltage drop through the diodes which is appx 1.5 volts.

 

I don't see the need for a bridge or any diodes in this application. The DPDT switch in the original schematic reverses the polarity of the DC supply requiring the bridge but why?

Please understand that many LEDs have a very limited reverse voltage tolerance. Often that maximum reverse voltage is about five volts. So I suggest never reversing the polarity to select which color gets used.

 

That's the purpose of the series diodes.

 

You don't need any diodes and use a SPDT switch with the center position OFF.
View attachment 306436

Assuming there are 3 wires between the switch and the lights. The purpose of this circuit is to make it work with existing wiring, which has two wires.

 

Assuming there are 3 wires between the switch and the lights. The purpose of this circuit is to make it work with existing wiring, which has two wires.

He didn't mention that there were only two wires available until post #7 and I presented two possible solutions in post #8.

 

He didn't mention that there were only two wires available until post #7 and I presented two possible solutions in post #8.

I thought it was obvious from the circuit, why else would all of those diodes be used?

 

If anyone is able to show on photos how this works, I'd appreciate the effort because this is over my head.

Is this diagram clear enough?

 

Is this diagram clear enough?
View attachment 307712

After the switch, the two lines going to the LEDs can be either + and - or - and +.

The diodes take the - from either line and route it to common. The plus from one line goes to the white, the plus from the other line goes to the amber. The common goes to the - side of both.

 

Does your light fixture have both LEDs installed with a common negative? If so it might be feasible to use the RV chassis as the ground connection eliminating a return wire.

If no chassis ground connection then using two fixtures in this arrangement only requires 2 wires. Which is the original circuit shown in post #1.
The switch reverses the polarity of the voltage applied to the fixture and the diodes steer the current to the appropriate LED. Only drawback is the voltage drop through the diodes which is appx 1.5 volts.

Didn't think of this, I'll take look.

 

Is this diagram clear enough?
View attachment 307712

Thanks, I'll try this today.

 

Is this diagram clear enough?
View attachment 307712

This is working, thank you very much.

I just needed to jump the +Pos and -Neg for it to work. I've run a test and all is well now.

 

Assuming there are 3 wires between the switch and the lights. The purpose of this circuit is to make it work with existing wiring, which has two wires.

It can not happen in a simple manner. Can be done, not with diodes, though

 

It can not happen in a simple manner. Can be done, not with diodes, though

I'm not understanding what you are trying to say, can you provide some context and maybe a drawing