Simple way to reduce 24vdc to 12vdc?

[RJ]

Aesop's Tortoise is getting new LED strip lighting in the front salon and rear bedroom.

In the process of removing the old fluorescent lights, I discovered that they have a 24vdc hot lead, which will most likely fry the 12vdc strip LEDs.

Anybody have a simple way to reduce the voltage where the LEDs connect w/o having to trace the wiring back to the main switch panel?

TIA,

RJ

[Lostranger]

We bought 24v LED lights on eBay. So far we have one long strip, several short strips and a gooseneck over the bed. We'll be getting more as the interior comes together. Lots of inexpensive options. We use a 24v to 12v converter for powering a cable modem, wireless router and phone chargers. I only use the converter when I cannot find a 24v option.

I'll eventually have a separate 12v house system with a single solar panel charging one 8D AGM. That's because the APU I'm going to install to heat and cool the back half of the bus and charge batteries uses 12v. At that point, I'll be able to eliminate the step down converter. Every time you change electricity, you lose some. We're 90% off grid, so we want to minimize unnecessary losses.

We had to wait for some of our lights to travel from Asia, but the shipping time and costs were reasonable.

Jim H.

[Debo]

Hi RJ,

I have a smaller 24 volt to 12 volt converter that I use to power a few things on my bus. I know Samlex makes a couple of different ones. I just looked on Amazon and they have them, but it looks like the price has gone up since I bought mine. You may be able to fine one cheaper somewhere. Mine will do 30 amps and is 24 volt right up to where I mounted the converter, so no real rewiring is necessary. Word of caution though. There's a little fan in it that kicks on for cooling and it's not obnoxious, but you can hear it.

[gumpy]

You could hook two of those 12v lights in series and run off the 24v feed.

[luvrbus]

I bought LED strips that say they are 11 to 30 volts (24 per ft) did I buy strips that are going to burn out ? they do seem to be dimmer on the 12v,plus they don't seem to work good with dimmer switches I purchased for the strips 

[Tony LEE]

Heap of DC-DC power supplies available on EBay for a few dollars. All sorts of current rating from a few milliamps to 25 amps  and variable voltage outputs and they are cheap enough to use one for each fitting.

The only disadvantage is they may cause interference on some AM radios

[LuckyChow]

FWIW, I've been using the bulb shown below on 24V without issue.  They are rated 10 - 30 volts.  I have 3 of them in service for two years. 



Here's the link to them if anyone is interested:

https://www.superbrightleds.com/moreinfo/s-series-bulbs/1142-led-bulb--single-intensity-dual-contact-45-smd-led-tower/906/#/attributes/2

I'm using them in the light fixture shown below for outside lighting.

[TedCalvert]

RJ:

You have been such a help to so many people on these boards, including myself, that I would be honored to attempt to help you on this.  

There is a device called a 3-terminal regulator which is a transistor-looking device which will take DC voltage input within its range and output its rated voltage.  It should work for this.

Quote from RadioShack's online catalog:
"Power up with this voltage regulator. May require heatsink in some applications. Output voltage is set at +12VDC at 1A.
Type: 7812
Case style: TO-220
Maximum Input Voltage: 35VDC"

LM7812 is the industry standard part number; RatShak says sold out online.  Look at Mouser Electronics or All Electronics, possibly they are better quality.  I am a firm proponent of NOT using any handy metal as a current-carrying return conductor, i.e. "ground", in a motor vehicle; rather returning to a good pathway back to the negative side of the source: battery.  More on that if anyone cares, lol.

Gumpy: that would probably work.  Keyword: probably.  Not sure with the electronics contained within the led assemblies.

luvrbus:  If the led units you have are self-regulated within that range, they internally adjust for the incoming voltage, they will not dim.

Most all led lights have some internal electronics, if not they would self-destruct as they are a very low resistance and must have some sort of current limiting. Like neon indicators.  They always had a current-limiting resistor in series. Kinda like fluorescent tubes.  You must have a ballast to take the power you have and make it suitable for the tubes.  It just that the 'ballast', if you will, is now microscopic and built in to the led.

Hope this helps.

Ted.

[bevans6]

Given the ultra low current draw of most LED lights, and their extreme reliability, I would simply design the layout so I could wire them in series, as already suggested.  If you don't already have the lights in hand, I would see if I could find some with a wide input voltage range.  My last choice would be any kind of remote electronic device to adapt the voltage, if only for future ease of maintenance.

Brian

[Dave5Cs]

RJ this is what Bruce had me get to drop the voltage to 12v from 24 VDC. It is a simple converter and you can run a bunch of different 12 volt stuff off it. It will keep any voltage that is higher than it from burning down the Bus. I got the cheap LED strips and was told that if i hooked them up without this that if the charger came on when the lights were on and it was say 14.6 while charging or spiked it could potentially heat up and burn them out or other bad stuff. They work well and are solid state.

Also if you ever need 12 volt most 5's are post 55 in the driver panel. Mine was 55 54 53.
HTH Dave

http://www.ebay.com/itm/DC-DC-Converter-Regulator-24V-Step-Down-to-12V-20A-240W-/140654732253?pt=LH_DefaultDomain_0&hash=item20bface3dd

[gus]

Aesop's Tortoise is getting new LED strip lighting in the front salon and rear bedroom.

In the process of removing the old fluorescent lights, I discovered that they have a 24vdc hot lead, which will most likely fry the 12vdc strip LEDs.

Anybody have a simple way to reduce the voltage where the LEDs connect w/o having to trace the wiring back to the main switch panel?

TIA,

RJ

Check the specs closely, some LEDs have a wide voltage range.

[Gerry H]

Well I toasted all my 12V LED replacement bulbs when I ASSUMED my luggage bays were 12V since most of the exterior lighting was changed from 24 to 12v BUT I failed to check and smoked them all in one bay. That's 8 bulbs in the trash. Can you say STUPID - after me! I wouldn't push it voltage wise. I will be keeping 12V LED's on a 12V supply. It was glorious for maybe 5 seconds! FWIW Gerry H

[Lin]

I would agree with the previous posts in this order:

First and easiest, get LED bulbs that work on 24 volts.  There are lots of them.
Second choice, wire two 12's in series.
Third, get a 24v to 12v device small enough to use at individual locations/
Fourth, get a 24v to 12v power supply wired in remotely for everything.

[bs4104]

Remember when charging you voltage will go up.   
14.5 volts on 12V.   
29 volts on 24V. systems.
factor that in too.
Bruce

[Emcemv]

Haven't seen this mentioned yet for something simple like a string of LEDs if you look at the specs and find out what current they draw, you just need a resistor in series with them to drop the voltage to 12v. You can calculate the resistor value by R= voltage divided by current so if the LEDs draw 100ma (0.1 amp) and you need to drop 12 v the. The resistor needs to be 12/0.1 or 120 ohms. The power rating required would be 12v times the current or 1.2 watts so a 2 watt rated resistor is needed. This method won't work for complex electronic loads but should work fine for LEDs as long as there is no dimming controls involved.

Bruce