DIY LED lighting fixtures
 

Hi all,

Wanted to show off some pictures of a more or less recent project :)

I built some partition walls around an open family room a few months ago, to convert it to an office. In the process of building the walls, I mounted LED transformers (one 48W and one 20W) to two of the studs, ran low voltage wires through the walls and ceiling (the light switches are switching 12V), and custom built some LED lighting.

I used this sort of LED module:

Warm White LED Module 12V Waterproof 5050 SMD 4-LED/PCS Light 20pcs $20.95 Free Shipping @GoodLuckBuy.com

They contain four 5050 type SMD LEDs each, run about 0.7W and output on the order of 60 lumens a piece. A string of 20 of them is around 20 bucks at the link above - I haven't found any LED lights for a lower price per lumen.

I cut a strip of 1/4" plywood about 2 inches wide and about 1 1/2' long, then glued 10 modules each on them (Loctite PowerGrab is a great adhesive for this, by the way!).
Then I cut a strip of acrylic about 1 1/2" bigger on both dimensions than the plywood (I use a jigsaw, since I never can get a straight edge with scoring and breaking the acrylic. Sprayed both sides with Krylon frosted glass spray, drilled 3 holes through both acrylic and plywood, and bolted a 1" binding post through each hole with a matching bolt from the back of the plywood.
The plywood is then simply screwed to the ceiling and the acrylic mounted on the binding posts with the same screws. The results are two fixtures in my office that look like this:

http://img820.imageshack.us/img820/4...0210213hdr.jpg

Uploaded with ImageShack.us
Uploaded with ImageShack.us
Then I just finished another one for the other side of one of the partition walls, which now forms a rather dark hallway with an existing wall. For this one, I followed the same procedure but different dimensions and used 12 modules instead of 10, and also glued a piece of aluminum L-profile to each long side of the fixture for a more finished look. Fast exposure that shows the LEDs:

http://imageshack.us/a/img507/2457/2...0202903hdr.jpg


And the end of the hall along with it:

http://imageshack.us/a/img545/2012/2...2822hdr.th.jpg

So far, I'm pretty pleased with the results. Next I'll build three more of these that will hang from decorative chains in my kitchen to replace the three fluorescent fixtures at 75W a piece I have in there now :)

Those look really nice! Sounds like you came up with a great way for a good looking fixture that is also quite inexpensive.

Where did you get your transformers?

I just ordered some parts yesterday for my first LED project. I have a staircase that I want to light up at night. I'd like to mount my LEDs under the handrail and have them illuminate the stairs. I'm also going to get a little fancy and use some PIR (passive infrared) motion sensors on each end so there won't be a need for any switches. I still have no idea what LEDs I'm going to use though.

I've used this one for the office, and a similar (smaller) one for the hallway.

Led Wholesalers Waterproof Electronic LED Driver Transformer 48 Watt 120 Volt to 12v 4 Amp

If you just do a google shopping search for 48W LED transformer (or whatever the wattage you anticipate needing is ;), these pop up. They're fully electronic, so they have a high efficiency and low heat output, have built-in overcurrent and short circuit protection, and work well :)

If you could do a write up on how to build one of these with a few more pics, I'd really like to put it on the blog.

Gladly. Do you want me to just post it to this thread?

OK, so here's the step-by-step description of my process - YMMV, of course, and there's plenty of room to change and improve :)

Building these fixtures is relatively easy, and the materials come out to about 20 bucks a piece - less if, as I did, you still have a bit of spare plywood and acrylic sitting in your workshop ;)
This is also assuming that you've got 12V wiring and power supply for the LEDs ready. I placed transformers in the walls and rewired the light switches with low voltage wiring (a regular light switch works just as well with 12V as it does with 110).

Materials:

1/4" plywood (about 7 bucks for a 2'x4' sheet)
A strip of acrylic (about $25 for a 2'x4' sheet)
1/2" - 3/4" binding posts and matching bolts (roughly $5 for 10 or so)
Adhesive (~$5 depending on type)
Aluminum L-profile ($6 for a 4-foot piece)
LED modules (Warm White LED Module 12V Waterproof 5050 SMD 4-LED/PCS Light 20pcs $20.95 Free Shipping @GoodLuckBuy.com - $20 for 20 of them)

Before starting to build, it can be useful to make a few calculations for the fixture. How much light do you need? Based on that, what kind of transformer do you need?

Number of modules = number of 15W CFL bulbs * 7
Wattage = number of modules * 0.7

For example, a 15W CFL bulb output about 400-450 lumens. In warm white color temperature, the modules linked to output in the ballpark of 70 lumens a piece. That means for the same amount of light a single 15W CFL produces, you'll need 6 or 7 of the modules.
Each of the modules consumes on the order of 0.7W according to the LED's specs (I haven't measured it), which means for one fixture with 12 modules, the transformer has to handle at least 8.4W, or 700mA at 12V. I've got a 30W transformer in the wall, so I opted for three fixtures with 12 modules each for a total of 25W - it's a good idea to give the transformer a little headroom (on the order of 5-10%), because the power consumption is going to vary a little from module to module.

This is the transformer I used:
Ledwholesalers 30 Watt LED Power Suppply Driver Transformer 120 to 12 Volt DC Output, 3207 - Amazon.com

Now for the fixture:

First, I cut a piece of plywood (I used 1/4") to the size needed for the fixture. The LED modules are about 1.5" square, so anything bigger than that will work - the dimensions really depend on the shape for the fixture, and the arrangement of the LED modules.

http://img69.imageshack.us/img69/159...1231140039.jpg

This doesn't have to be pretty, as it'll be mostly hidden from view. Painting it the color of the wall before mounting the LEDs will make it nearly invisible. I imagine you could use any other substrate for this as well (like a second strip of acrylic), but the plywood is easy to work with and I had some spare strips.

Drill at least two holes big enough to fit the bolts for the binding posts. The amount and location depends on the desired look and size - the bigger the fixture, the more are needed to keep the cover solidly attached.

Next, I cut a strip of acrylic to size. This should be about 1" bigger in both dimensions than the plywood. To cut, I use a jigsaw because it gives me straighter cuts than scoring and breaking the acrylic - clamp down the acrylic with a board to use as a guide for the saw. Use a fine toothed saw blade and go slow to prevent the acrylic from chipping.

http://img560.imageshack.us/img560/3...1231140154.jpg

After cutting, clean both sides and spray with frosted glass spray. Two coats is usually enough to get a nice frosted surface. It's a good idea to do this outdoors - not only are the fumes from this stuff pretty gnarly, it also prevents some of the dust undoubtedly floating around in the workshop from settling on the wet spray and messing up the finish ;)

http://img4.imageshack.us/img4/5958/20121231140254.jpg

While the acrylic is drying, we can mount the LED modules. They come in a string and can be a pain to mount because you end up pulling the previous one out of position with every one you glue. I can highly recommend Loctite PowerGrab for a job like this - it's got really strong tack while still wet, so the modules are less likely to shift around until the glue is dry.

http://img15.imageshack.us/img15/323...1231140122.jpg

I squeeze a small amount of the adhesive on the back perimeter of the module and then just press it in place with my fingers. A few pounds of pressure are enough to make it stick well, and they won't move easily after that. Arrange all the modules on the plywood, making sure to not cover up the holes drilled for the binding posts and bolts.

http://img4.imageshack.us/img4/4867/20121231140408.jpg

After all the modules are in place, bolt a binding post through each of the holes. The cover will later attach to these.

http://img203.imageshack.us/img203/1...1231140543.jpg


http://img687.imageshack.us/img687/1...1231140655.jpg




Now I put the frosted acrylic on top of the binding posts in exactly the final position to mark the holes for drilling. Drill holes through the acrylic where the posts will go - start with a small drill bit, go slow, and use very, very little pressure, otherwise the acrylic will tend to crack. Then expand the holes with a bit matching the size of the bolts. Clamping down the acrylic is a good idea, as it tends to be pulled up the drill bit and slam into the drill once the bit goes through otherwise.


With that, the back end is complete. At this point, I already screwed it to the wall with a few drywall screws and wired it up.

Next, I took a piece of aluminum L-profile

http://img72.imageshack.us/img72/676...1231140750.jpg

and cut two pieces about an inch longer than the long sides of the fixture. File off the ends to
Put a small amount of adhesive into the inside corner of each L - just enough for a thin layer, so it doesn't ooze out the sides and become visible from the front - then press the frosted acrylic into it. At this point, I weighed it down and let the glue dry for a few hours.

http://img854.imageshack.us/img854/4...1231140941.jpg

http://img707.imageshack.us/img707/7...1231141113.jpg


Finally, attach the cover to the fixture by bolting it into the binding posts. Done :)

http://imageshack.us/a/img507/2457/2...2903hdr.th.jpg

In addition to the wall fixture, I've also got two ceiling fixtures built the same way (but without the aluminum profile along the sides) in my office:

http://imageshack.us/a/img820/491/20...0213hdr.th.jpg

Awesome write up, thanks!

I do have a few questions though:
The LED website says each module only uses .3W, but you say .7W. Why did you quote a higher number?
Also, the site you linked doesn't say that each module puts out 70 lumens. Where did you get this info?

As for the wattage, ir's because I think the seller's web site is wrong. The 5050 type LEDs are spec'ed at 0.19 watts (Warm White 5050 SMD LED | Component LEDs | Super Bright LEDs), which makes a little over 0.7W per module.
It's important to keep in mind though, that 5050 is just the size of the chip - different manufacturers mame 5050 LEDs with different characteristics. In this case, I figured it is better to err on tbe high side. My multimeter is broken, but I'll measure current through o e module when I get a new one.

For the luminous intensity I used the 6000mcd and 120 degree beam angle from the spec, converted using an online converter, and subtracted a few percent to err on the low side of the intensity ;)

OK, so I just connected a 1 Ohm resistor in series with one of the modules, then measured the voltage across the resistor as 0.08V.
Ohm's law says that

I = U/R

So that makes for 80mA of current through the module. The voltage across was only about 10V, which makes for about 0.8W for that module. This was for a cool white with ~10000K color temperature because that's what I had laying around ;)
The warm white have on the order of 3000K color temperature, and I anticipate them drawing a little, but not significantly less current. Looks like the specs aren't too far off - tolerances notwithstanding, it seems 0.7W is pretty close for the warm white LEDs.

I just measured the resistor as well, and it actually shows at 1.2 Ohm, which brings us to

I = 0.08/1.2

So around 66mA for one module, or 0.66W at 10V.

Thats what I figured, thanks for clearing it up. :)

Either people need to quit posting such good info or I need to quit reading them. My project lists keeps growing - how to you folks find the time to do all this stuff? :)

Great info. Thanks.

Haha - primarily weekends when I have them :P

The holidays have been a good opportunity to take on some of this stuff. Now that my heating system is in place, I can concentrate on moving more of the house to LED lighting - the kitchen is next!

I hear ya though - in addition to the lighting all over the house, I've still got crawlspace insulation, office shelving, and a fireplace renovation on my short list. Sometime over the next four years or so is also hydronic heating and new floors upstairs, staircase refinishing, a complete kitchen overhaul, and a patio renovation. Seems like once you own a place, the renovating and tinkering never stops...

Very nice project and write-up! Looks like I will do the same to light up my hallway and dining. Thanks for sharing this with us

Glad my tinkering is of use to others :)

Yes these lights looks very impressive. How expensive these lights are?

Economies of scale play a role here. Since you're unlikely to be able to buy a single strip of acrylic and plywood of the right size at a good price, building a single one is nearly as expensive as building 5 or 6 of them (not taking the price for th LEDs into account ;)

The writeup lists rough prices for the materials. All in all, it should be less than $20 for one fixture if you buy 24"x48" sheets of plywood and acrylic and just build as many fixtures as you can make out of that. That's also assuming you've got the power supply already taken care of - needing only one transformer for multiple lights keeps the cost down.

By the way, I've got some really cool new transformers:

http://img20.imageshack.us/img20/287...0107094034.jpg

I'm going to use one of these for my kitchen lighting - these go for on the order of $15 a piece. 75W, and they're small enough they could conceivably fit inside a light switch!
If it does fit, I won't have to make another hole in my drywall, and I'll always have easy access to the transformer in case one does go out over the years :)

Caution
 

I believe it against any electrical code I have ever seen to enclose junction boxes, transformers and splices inside of a wall. Just something to think about.

Interesting... What do you mean by enclosed in a wall? I mean, junction boxes and switches by definition have to be enclosed in a wall - what am I misunderstanding?

Junction boxes
 

Enclosed in wall means covered and inaccessible. A junction box with a screw cover can not be covered or enclosed as to be inaccessible by normal means. Covered with drywall. Anything that has a splice can not be inside of a wall without normal access. The cover or access point must be visible and indicate that it is an access point.

Ah, I think I get it. So if I had the transformer in the wall and only the wiring connections in a junction box with a screw plate, that would still not be enough since the transformer itself needs to be accessible and hence inside of a junction box with a screw plate accessible from the outside?

That means that any transformer that is too big to fit inside of a junction box is a no-go to begin with, am I understanding you correctly?

Junction Boxes
 

Yes, transformers in particular produce heat and can short circuit or start on fire. New electronic transformers are not as prone and the newest codes may have exemptions as such. Connection such a solder or wire nuts are what they don't want t be enclosed as well as they are prone to being loose and creating hot connections.

Things like door bell transformers are typically located in the attic mounted to an octagon box exposed in the open air.

I would check with your local code authorities as they will be the governing authority.

Yeah, I've got all the connections in junction boxes, but not the transformer itself. I guess I'll have to redo that part :)

Before I installed it, I was a little concerned with the current through 12V wiring, but taking into account that in the office I'm only running about 2.5A through the wires (14ga stranded) if all lights are on, I'm not too worried.
The kitchen is going to be closer to 4A total - I expect to use the existing 14ga solid core wires and just transform directly before or after the light switch, so that shouldn't pose a problem either.

I like how well the lights turned out, with your new transformer size it should fit in a deep switch box behind your light switch very nice. I agree with leave your normal house wiring in and transform at the switch box then 12 volts to switch and so on. I would think you could then also use ground from 110 side to switch. question about mounting leds, could you use the holes in the center and add stainless screws to hold them in place? What if you run a thin strip of aluminum under them between the leds and wood and if you are going to use the home wiring use the ground and mount to strip? this way the whole system is grounded all the way back to breaker box in case transformer fails or ect. maybe to much but I dont think it could hurt? Again very nice

Interestingly enough, the transformer itself doesn't have a ground wire, only hot and neutral. It's in a plastic housing, so I guess they deem it unnecessary - on post-transformer side, if you ever end up with current going through something touchable, it's only 12V, so grounding isn't as crucial.

In the kitchen, I'm going to use the existing Romex from the switch to the lights. The light switches themselves are going to be grounded if I transform after the switch - I guess I could hook the ground conductor from the lighting wires up to the incoming ground and ground the modules through that, but I don't think a module failure that would have 12V running through the module backplate is very likely.

You can conceivably use screws to hold the modules in place. In fact, you could directly screw them into drywall - they only get a little warm to the touch. I just decided on gluing because it was easier with the mounting method I used ;)

Unfortunately the transformer I posted a picture of isn't going to work - turns out it outputs 12V AC, which these modules don't work with. I've ordered a different one which should fit into a 6" switch box (it's 5.1"x2"x1.5"). I'll post about installation as soon as I get it (should be about a week).

Just a thought but instead of putting the transformer in the switch mount if you can on the back of the lighting mounts you make? like the one you put into the ceiling, I know in my area anyways as long as you can access the transformer or splices your good for code. Like any normal light fixture the wire splice is in the ceiling and covered with the light fixture and to access all you need to do is remove fixture. Mount transformer on backside of your plywood were wires from ceiling come out, you could even put in a junction box for the transformer and connections, that way you dont need a 6" box at a switch that will be 3 times bigger than needed and not look as good, also if you or someone else ever wants 110 back to that light source they just have to remove the transformer and install different light fixture.

I've thought about that, but then I'd need 3 or 4 transformers just for the kitchen. I figured it would be easier to just use one for all of the fixtures ;)

Im caught between building them or buying the bulbs. After you build and purchase the transformers the cost is high compaired to the bulbs that you could connect into any 110 fixture. I bought one of the really cheap led light bulb type on ebay just to see and it works fine, but still like the idea of building my own. Is there a reason you choose to build your own instead of purchasing them say safety or just for the the fact of building your own and design?

For several reasons in my case. Primarily, the location is a new partition wall with no existing fixtures, so I'd have to shell out for the bulbs and fixtures (and man, are decent looking light fixtures expensive!).
Also, I wanted something that would fit well into the spot visually and not protrude into the hallway much. It was just difficult to find a fixture with the shape I was looking for ;)
I also had most of the materials already available - Plywood, acrylic and the frosted glass spray were left over from previous projects, so that made it quite a bit cheaper, too. For the kitchen, I plan on building because again, I'll need new fixtures to replace the pretty ugly ones in there right now. I've still got enough acrylic, which should make the total cost for three similar fixtures for the kitchen about $80 or so, everything included.

Keep the updates and pictures comming like to see how it turns out and good luck.

Recycle an old fluorescent tube fixture
 

Here's another idea for enclosing the LED transformer and providing a heatsink for the LED's.

Recycle an old Fluorescent tube fixture, the long white steel box kind. Go to you local Habitat For Humanity Re-Store or equivalent appliance salvage place and find a suitable size fixture, they should be quite cheap. The fixtures are generally made of white painted sheet metal and are almost certainly a UL-approved design. An added bonus if it has a light diffusion cover that you like.

Remove the old fluorescent ballast, replace with the new LED transformer. Drill and mount your LED modules on the top cover. Reuse the light diffusion cover or make something better. Test, mount to the wall and Ta Da!

That should provide a solid, easy to mount structure for the light, meet code requirements and look clean and finished. Tell me if I missed something obvious.

FWIW,
Tim

Hi Opiesche,
I've been thinking about the whole transformer location problem (now you're in trouble) and found a way of reframing the problem. I'm assuming you want to have the light switched. Doorbells also use transformers and they are typically housed in attics, or in your about to be beautiful crawlspace. You can install a butt ugly electrical box up there or down there as long as you've got access to it and it is not covered up by anything. Like doorbell transformers you should wire it always on.

Again, like doorbells you don't need to have UL approved wiring practices for 12 volts. You could just run the fairly small guage wires through the ceiling or floor next to the wall to a local switch box used for the rest of the lighting. You could make a narrow cut in the drywall with a circular saw, or whatever and embed the wires in the drywall and plaster over it. No big overhaul neccessary. If you don't want to expand the existing box holding the existing lighting switches to add a switch then you could just replace one of the switches with a double pole switch. Run the wires that went to the original single pole switch to just one of the poles of the double pole switch that replaced it. Connect the 12 volt hot wire and light hot wire to the other pole of the new double pole switch.

You could do that for retrofitting all low voltage transformers you need to install. Then label them and keep them all located in one out of the way place. This kind of installation would work best for retrofitting installations where you don't want to rip and tear things apart. Also this would not work for lights attached to multiple three way switches. They don't make double pole three way and four way switches.

EDIT:
It may not be such a good idea to use one double pole switch running 120 and 12 volts together. If the switch ever became defective you would have the possibility that you'd get 120 ac running back to the transformer. If the rectifying diodes blew in a shorted state then you'd have 120v ac going into the secondary that would get boosted to 1200v on the primary. It's all a remote possibility but its definitely a possibility. That situation would definitely be lethal.

I just thought of one additional possible benefit of locating all led transformers in one central location in the attic or crawlspace. If one ever decided to have backup lighting for power outages then you could use this central location to hook up, as an example, a 12 volt battery. Even in a grid tied solar system, it would be convenient to have at least one or two solar panels that feed a dedicated backup power system. Those panels could be used to charge some conventional car batteries, instead of the hugely expensive deep cycle batteries used for whole house non-gridtied solar systems. (Those battery expenses are what keep me from entertaining the building of that kind of PV system.)

In this kind of simple backup system there would be no need for a complex automatic switching system. Instead just install switches at the input and output of the transformers. The switch in front of the transformers would simply disconnect it from AC power, a safety switch. The switch after the transformer would switch from the transformer output to the 12 volt dc input. The output of that switch would go to all the 12 volt circuits.

It goes without saying that this would be a lot of work so it would be better to get one fairly large 12 volt transformer to feed all neccessary 12 volt circuits. This would eliminate the bank of switches you would otherwise and would reduce the complexity enormously. Less stuff to go wrong. So, finally, locating all 12 volt transformers together could have big benefits down the line if you are the ambitious type. If enough people are interested maybe this topic should be put into its own thread.

This idea would also work for non-photo voltaic systems. It would give backup power when power goes out. You could scale it up for other uses, such as powering a minisplit, but it would come at the expense of simplicity and efficiency. That's because you would probably need an additional inverter and a bigger overall system to power it. At some point you have to decide where the dividing line is between beautifully simple and Rube Goldberg.

Thanks for the thoughts, Exeric! I've been considering putting the transformers into the crawl space - it should be easy enough to mount them directly under the wall the switch is in, drill a hole upwards, and run the wires through there! For retrofitting the hallways, I might do exactly that.

For the kitchen, I've put the transformer about 1 1/2 ft below the switch on the other side of the wall, into a junction box in the wall in a closet. The supply wire comes from the switch box, is spliced off down into the new box that houses the transformer, and 12v come back up into the switch. For the fixtures (one is finished) I'm just using the existing Romex wiring and extend it from the existing ceiling box to the fixture:

http://img521.imageshack.us/img521/6...3175018hdr.jpg

Of course from the ceiling box to the fixture needs to be wired properly - I need to run the 12V wire through the ceiling a short distance because the existing ceiling box isn't in the location I need it in. Darn builders, and their habit of not considering the outlandish modifications I might someday plan on!

For the kitchen fixtures I decided to go with self-adhesive LED strips instead of modules, because I wanted a higher density of LEDs (and higher output along with it). I picked one with 600 LEDs @ 2A for 5 meters (http://www.ebay.com/itm/220768031684...84.m1439.l2649), and ran three strips of a little less than 3 feet in length, for a total of about 350LEDs, so on the order of 1.2-1.3A (should around 15W or so).

The single fixture shown here throws about as much light as a single one of the original 75W fluorescent fixtures, maybe a little less - but since it's more directional downwards, the work space is nicely illuminated. I need two more of these (a little shorter) for a total of about 40W or so, replacing the three original fixtures at 225W combined. I don't understand why this sort of thing isn't done everywhere all the time in new construction.

Really nice job and well worth keeping in mind for a shameless copy. :)

When you say the light switches are on the 12V side of the transformers, you mean the transformers are running all the time?
Not very efficient, though. I'd just put up with 120V mains switching as it's properly 'off' when it's off.

Yes, the transformer is running. If I can get to it this weekend I'll try to measure the unloaded draw of the transformer. I anticipate near 0 though (just from experience with other electronic transformers) - the reason I'm switching the 12V side is that the transformer takes about a second or so between getting supply and outputting to the load. That's a bit annoying, so I decided to switch the transformed side instead ;)

I see your point and for sure, delay in lights coming on is very annoying.
I wouldn't trust an unseen electronic x-former as far as I could throw it - capacitors fail and blow out; they overheat smoulderingly and quietly in the hidden spaces they get stuffed into. Out of sight, out of mind, as the saying goes.
Otoh, a simple wound x-former has a lot going for it (assuming it's decently made) but it's less efficient. Having said that, there are millions of old bell x-formers that haven't burned down their owners' houses yet; although I know for sure that it has happened.

I have had great success with these:
New 12V 7W 50cm SMD 5050 Pure White 36 LED Strip Light Aluminum Alloy Shell | eBay

or, search: HRK 7.5W 5050LED

I originally bought a few to replace failing ccfl assemblies in flat-panel monitors. The assemblies do well, running off the same supply rail the ccfl high-voltage supply previously used to power the backlights. The replacement ccfl assemblies were on the order of half the price of a used monitor or more, the LED assemblies run around $10 a meter. With a lifespan approaching 10x the life of a fluorescent, they should never need replacement again. I can see plainly why the tv manufacturers are switching to LED.

These little buggers are awesome! They put out the same lumens as a 40 Watt incandescent, yet use only 7.5 Watts, and will last for decades. they are water resistant, and can be chopped into shorter sections if needed. Each 3 LED section can run separately off of 12 volts. They are available in lots of shades of white, depending on your needs or taste. Two of these strips laid next to each other at a right angle will give you 180 degrees of coverage at about the same intensity as a T5 fluorescent of the same length. I imagine in a few years you will be buying screw-in LED bulbs for the same price as compact fluorescents.