DIY | 12v Large LED Cabin Light




Introduction: DIY | 12v Large LED Cabin Light

About: I'm a Nerd and a garage inventor. My dad used to say, "There he to 'The Lair' to invent something. Try not to burn the house down, OK?" I am a Graphic Designer & Illustrator from the South. I love…
$42 DIY | 12V LED Cabin Light (with wall-washer style night light)
12" Wide x 36" Long x 2 3/4" tall | 72 Watts @ 100% | I use a PWM Dimmer for a power range of 3W to 71W
for use in Houseboats, RVs, Garages, Laundry Rooms, Workshops, Artist's Drawing Areas

One of these is installed above each of these locations: my drafting table, my electronics workbench, and on my friend's houseboat.

If you've had a chance to check out the article I wrote on how to build a small cabin/bunk LED light fixture ( then you will recognize this baby.  This is a larger LED fixture designed to be used in the main cabin of an R.V. or house boat.  It also works great as a work, garage or laundry room light. It is only 2 3/4" thick, 12" wide and 36" long. 

It was made from:

1x reel of Warm White LED strip lights (300 count, SMD5050, non-waterproof) (Ebay for $16) -> ~71W Power Required per reel
4 feet 14 gauge wire ($3)
2x Push button On/OFF switches from RadioShack ($5)
1 plastic lens from a fluorescent lighting fixture ($9)
12"x36" piece of plywood (scrap)
12 brass screws (on-hand screws)
1x4 oak board cut to give four sidewalls with a groove down the outside of the long sides for LED lights (scrap lumber)
walnut stain (on-hand stain)
1 thin sheet of steel to use inside as a heatsink for the LED strips - Optional ($9)
electrical tape (HQ only - on-hand)

Total cost:  $42

I have this installed and working on a friend's house boat presently.  It uses one 12-volt marine deep cycle battery for its power needs (see descriptions in photos).  This battery is then charged via solar charger & panel (20W) during the daytime.

The unique feature this unit has is the two-light option: one power button for the downward-facing cabin light and another for the side-facing night lights. The entire fixture is connected to a dimmer, then a fuse, and then to the battery (see diagram).

How much power does it really take to run the LED lights? This light consumes ~71W (@12v) running at 100% or as little as 3W when dimmed really low with a still usable brightness. The light emitted is pleasant, not harsh due to the warm white style chosen. Additionally, the color is consistent across the power range with little, if any, deviation in light quality. So, at 25% the light is as pleasant as at 100%.  This isn't necessarily true of some LED bulb products I've purchased in the past, but using these strip lights with the hardware shown in the diagram I have been very satisfied. It's almost crazy to think that I can make my own fixtures with my own choice & quantity of LED's (including RGB with remote) and come out with better quality light with only 12V as the source power. I have used some 120V home products and have not enjoyed them as much as this one.

What is different in the construction? The build is essentially the same as the small bunk light, so I won't repeat all those steps. Click HERE to read the other well-documented article. The only major variation is that I designed a channel along the long length of the outside so that I can embed a strip of lights to act as wall-washers for the ceiling (see photos). These lights are optional. They also use their own power switch to give the end-user flexibility.

Contest & Build notes:  It would have been easier to use a laser cutting system on this to get pieces trimmed perfectly--especially the steel sheeting we used for a heat sink and the acrylic lens cover. Also using metal or premium woods for this fixture could have made for a more elegant look and feel, but the results were very nice indeed.  The finished oak matched the new flooring and counter tops very well in the cabin.  If you want to build something similar, you can most likely use the materials and tools you have available.  If you do have access to a nicer materials and equipment then push this further and please share your results for everyone!

►Q's?  If you have any questions about building this light (or other projects I've made) or what steps I took to do so, please ask. I am more than happy to share and to help you get your project up and running. Please don't beat your head against the wall for very long!

Thanks for reading and if you build anything inspired by this project, please post your photos.  Don't forget to include your family members or friends when you build a project like this.  Share the fun & the work!
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    6 years ago

    I like your suggestion of using an old PC power supply, but both of my old PC power cords say they output 19v. Won't that overheat 12v LEDs?

    Ken (I'm a novice with LED strips.)


    Reply 6 years ago

    Hey Ken! It's nice to hear from you.

    Yep. 19V will ruin it. And in a hurry too.

    Are you talking about a wall-wart power supply or a laptop power supply?

    If so, that may not work as most of them output more than 12v. Not only that, but over time those puppies heat up and some can cause fires or burn out altogether after they age. Quality control on some of those units is not always as good as it needs to be. Typical output voltages for DELL and HP models are usually 18v, 19v, 24v and some are in the 30's.

    If you really have to use one of those, get a voltage step-down/reduction module from eBay to put in front of your led strips. This will allow you to finely adjust the voltage for your project to 12V. Oh yeah, get one that supports your wattage needs.

    This is what I do:

    *I just use a standard ATX PC PSU (power supply). The standard old boxy style. By using a standardized ATX model, the wiring conforms to widely available online diagrams and it is easy to label and use the wires.

    ATX units also output power on at least three levels:

    +12v (yellow wires)

    +3.3v (orange wires)

    +5v (red wires)

    This is the better option for LEDs as those are dirt cheap, sturdy, standardized and easily mountable. They can be had from any old junker PC that most people are throwing away for free. Not only all this, but they can handle large loads at 12v.

    There are some decent instructables that show you how to wire up an ATX supply so that it has an on/off switch and an indicator light. Some are great for reading to see how you want to make your power unit.

    If you go to ebay or amazon and buy a small inline LED voltage meter for under $6, you can have that on one of the 12v outputs to show that you are indeed sending out 12v. It's a nice diagnostics feature.

    Here are some search links on how to do this. You can make it as complicated or as easy as you want really. But let me point you in a good direction:


    I personally leave the power cables intact and extending from the ATX PSU unit. I snip off the motherboard connector and group them from there and solder them to various plugs or connectors that are necessary to the project. Some heat shrink tubing and/or plastic-weave wire sleeving adds a very nice touch and can prevent trouble later on during an install.

    **You can always google or search YouTube for visual tutorials for ATX lab or bench Power supply projects or ATX regulated power supply projects.

    Good points to remember:

    + Just make sure the wattage support for your ATX PSU is a good bit higher than what you are planning to draw with your lighting rig. A good rule of thumb that I have always followed is that I want 1/3 higher wattage rating (or higher if I can afford it) on the PSU than what I am going to load onto it with lights. This helps it not get too hot and also gives room for growth later.

    + Don't run a PSU at full load - 100% max rating of it's wattage. It needs headroom.

    + Be sure to use fuses in your LED circuit. Some people have left them off and that's not a good idea.

    + Always use grounded AC electrical cables for the source power.

    + Do install a power switch and an indicator LED.

    You can search Google Images for "ATX power connector pin-out" for more info on what wires do what.

    I hope this helps! If you need more help, please send me a msg and I will contact you shortly.


    9 years ago on Introduction

    Very, very nice! You said your friend's solar panel was 20W. What size deep-cycle battery do you recommend, considering that I'm a night owl?