DC Lighting & Voltage conversion

[Liquid Asset]

We are in the process of redecorating the interior. While doing this, all the lighting is getting replaced. We have used some puck lights for the AC voltage and they also can accept DC Bulbs. I want to use these, but they bulbs avaliable are only avaliable in 12V and 24V. The Puck lights use G4 buls and I need to step down the voltage on 3 seperate locations.

Is there a way to step this voltage down? I dont have a lot of space, and a Newmar votage transformer woudl be hard to fit. Not only that, they are awful expensive. Is there a less expensive and smaller transformer? I can reduce the voltage to 12 or 24 volt. It does not matter. Is there any way with resistors to reduce the voltage? Even if I had to put a resistor in front of each light, that would be ok.

If I can do this with resistors, how do I determine what resistor to use?

 

[Brian Degulis]

Hi Pat I asked that same question a while back. I needed to drop the voltage on some panel lights from 32V to 12V and asked how to figure out the resistor size. I never got an answer and ended up going trial and error to figure it out. There is an electronic supply place on 12th st in Sarasota it's kind of a hobby shop for electronic components. The guy that runs it is friendly and smart and has the stuff I'm sure if you brought him a buld he could help you. Another thought would be to wire 3 12V bulbs in series. Wired like that the 3 bulbs would require 36V so 32V would be just a little dimmer but it would work.

If you need the name of the place just PM me I have it at work.

Brian

 

[Liquid Asset]

Brian,
I heard Sarasota Electronics on 12th Street closed? I just called my buddy and he told me what resistor size I needed.

The issue that he is explanign to me is that I need to make sure that I encase the resistor in someting because it will get too hot. Any Ideas what I can encase the resistor in?

 

[Brian Degulis]

Well that's a bumer if they closed I liked that place. Mine got warm not hot I think I would just try it first I think if you route it so as to seperate it from other wires it will be fine.

Brian

 

[TedZ]

To the best of my knowlege i have answered this question every time it has been asked.

Use this calculator. http://ourworld.compuserve.com/homepages/Bill_Bowden/r2.htm

Google "voltage dividers" for an education. Supply must be DC. Resistors have to accomodate the power of the light. This should not be much of a problem with big resistors.

If the supply is AC you must use a transformer and then rectify it to make a half decent DC. Can be lousy DC (i.e. lots of ripple) and still light a light bulb.
Rectify it with a decent sized diode. Once recitified voltages are lethal pre voltage divider. Be careful or buy a wall wart and cut the plug and connectors off it and wire it in.

Ted

 

[krush]

You also may be able to get a voltage regulator chip or something if you can find with that can handle the wattage.

 

[Liquid Asset]

thanks for the help. I need a 10 Watt 10 ohm resistor to drop the voltage to 24 Volts. Hope this can help anyone in the future.

 

[TedZ]

I would love to walk away from this thread, but...

You imply you have an AC source. I assume you are going to put the resistor you talk about in series with the bulb.

Resistors in AC circuits are not common unless you are talking about toasters (stoves, burners etc.). You are going to generate a lot of heat and you are not going to get DC if that is what your light is looking for. You realize i'm sure that 10 ohms is essentially zero ohms, i.e. a short. If the bulb is highly resitive when operating fine but if you wouldn't hook the AC directly to the bulb using a 10 ohm resistor in series doesn't change anything (practically speaking).

If you want to help folks and we are all appreciative of that, hook it up and tell us how it works out and exactly what the details are.

Thanks.

Ted

 

[Liquid Asset]

I do not want to use all AC lighting. I want some lights to be DC. The DC lighting is the votage that I need to step down to 24VDC. I apologize if that was not clear.

 

[Sonny]

Sounds to me like you have 120VAC at the light fixture and really want 24VDC. If this is the case it would be a lot simpler to take the other end of the wire off of the 120VAC panel and move it to the 24VDC panel. Only do this if the wire is of the correct size. Use a wire guage calculator to determine this.

 

[SKYCHENEY]

I think some of you are making this more difficult than it is. Hatteras usually ran line voltage to some fixtures and low voltage to others in the same room. This provided lights from either source depending on if you were plugged in to shore power/generator or not. What Liquid Asset wants to do is to just run his new 24v lights off of a 32v feed. The 120v lights in the same room are a totally separate system.

 

[stormchaser]

Maybe I read it wrong but I think he has both AC and DC lighting. He's replacing the DC lighing but the lights he wants dont have bulbs available of the correct voltage and he needs to step it down to 24v...the AC lighing is not what he's asking about. Maybe I misunderstood?

Oh...tip...if you want a GOOD 120v (or 240v) to 12v converter...and don't need a huge amount of wattage available...you a computer (PC) power supply. All of the "stuff" in a PC runs off DC of 12v, 5v, or 3.3v. Each power supply will have several 12v outputs (for connecting to drives) and can be sized up to about 70amps of 12v DC power and it is GOOD power. I'm a computer geek by trade and have used PC power supplies many times on boats.

 

[REBrueckner]

"I need a 10 Watt 10 ohm resistor to drop the voltage to 24 Volts. Hope this can help anyone in the future."

I hope everyone realizes this applies to a specific size (wattage) bulb and a specific voltage supply value. It is not a generic solution.