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I've spend some time googling, but the ROI has been low.

I want to make my own ceiling lamp -- I probably remember just enough electronics from Uni to get into trouble, so I'm trying to find a good howto -- an outline of how to design and build a lamp (the electronics and lighting characteristics, not the mechanical bits) without too much trial and error.

As I look through an online catalog, I find myself questioning:

  1. How do I choose the light type -- spot, strip... what are the tradeoffs?
  2. How many lumens do I need?
  3. How do I know if a light is dimmable?
  4. How do I connect it to my household power supply (overhead light lines, not via a socket plut).
  5. What aren't I thinking of?

Can anyone point me to a good reference, howto, starting place?

  • Are you planning on using off the shelf, screw in LED light bulbs that run on mains voltage, or are you going to be using the actual LED electronic component that uses low voltage? In other words, how much are you "building"? – JPhi1618 Dec 30 '15 at 14:02
  • I'm up for both. I studied physics and had some EE labwork some 20 years ago, so I'm sure I can figure out the electronics with a bit of a primer -- but I'd be interested in knowing if it's worth the effort from someone more aware of the current state of things. I figure I'll be making more than one of these. – Spacemoose Dec 30 '15 at 14:13
  • Ok, I ask because answer to question #3 is either "read the package" or "design it to be dimmable". I would suggest using LED lights that are made for 12v DC. There are several types, and will save you a lot of design time because they have integrated drivers and will be cheaper to buy than you could make them for. – JPhi1618 Dec 30 '15 at 14:16
  • The high power LED's that most commercial lights use are different than the discreet LED’s used in training classes. They have many different voltages now where it used to be 1.7Vdc and the current draw requires a large DC supply. Many of the units need temperature compensation or monitoring because of the heat generated. I have built underwater flashlights and saved $ . But not sure if you could really save and be safe for a home lighting project. – Ed Beal Dec 30 '15 at 14:24
  • My priorities are beauty and suitability of purpose -- financial savings would have to be pretty significant to affect the decision. More concretely, I want to maximize energy efficiency and lighting characteristtics, and minimize the noticeability of the electronics. I'm enough of a nerd that making my own circuit appeals to me, as long as I still satisfy those criteria. I know what I want to do in terms of the lamp design, but I don't know ANYTHING about the lighting part of it, so I'm looking for a good not-so-dummies guide. – Spacemoose Dec 30 '15 at 14:36
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You've got five different design factors, all entangled.

  • The heatsink. That will be a ruling factor in your design.

  • The user controls, light switch, dimmer, HomeKit interface, WiFi antenna, and whatever else you care to dream up.

  • All the physical parts and aesthetics of the fixture.

  • The LED emitter itself.

  • The power supply (driver) which takes line power and makes constant current tailored for that emitter. Any dimming etc. comes in here also.

I have good news for you: the last two can be purchased "off the shelf" from a variety of vendors from Mouser Electronics to eBay. It's possible you could innovate in this area, but you don't have to.

The other three are physical crafts, not electronic ones. Well, except for the user controls, where you can go crazy with "Internet of things" type technologies if you wanna. There's a lot of potential fun in this area, remembering that color LEDs are available. (their CRI is not as good as decent white LEDs, keep that in mind, so if you're looking for an excellent daily light, you might want to either forget about color, or put two emitters in your light. Emitters are cheap.

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This is one of those things that's not particularly practical to DIY, though of course you CAN DIY it.

All LEDs (bare, DC) are "dimmable" - the trick with making an AC-connected LED-fixture dimmable is all in the power supply design. When you DIY that, you are biting off a considerable bit of advanced electronics, and you're probably also making yourself liable if the fixture causes a fire, since you presumably won't be spending huge gobs of cash to get it UL, CSA or whatever applies where you are Listed. So you need to make sure it does not, can not and will not be able to be blamed for a fire, or your insurance company will do exactly that and fail to pay.

For decent-quality LED lighting, most of the hard design is thermal design. Keeping the device in the safe operating region while providing adequate light out, and perhaps also trying to keep it somewhat safer than that to reduce the rate at which it "ages" and puts out less light over time. Optical design can be an additional consideration, depending what the light needs to do.

How many lumens and light type you need are not answerable questions - it depends on what the fixture is supposed to do.

You can (fairly easily) buy various bits of generally low-perfoming (sometimes cleverly made to look vaguely like better performing) LED lights from ebay and stick them together, but they will generally not perform anything like a well-built fixture. UL marks on the power supplies, if present, may or may not be counterfeit.

You can buy high quality high-power LEDs from reputable suppliers and custom-fabricate heat sinks and circuit boards (sometimes one and the same.) It's a non-trivial undertaking. Dive into something like this and see how you feel coming out the other side: http://www.cree.com/~/media/Files/Cree/LED-Components-and-Modules/XLamp/Data-and-Binning/ds-XPL.pdf

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