DIY LED lighting fixtures

[mag7mm308]

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

[TimJFowler]

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

[Exeric]

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.

[Exeric]

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.

[Exeric]

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.

[opiesche]

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:



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.

[Incidental Damage]

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.

[opiesche]

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

[Incidental Damage]

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.

[jeff5may]

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.