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What's the context here? Are you somehow reducing power to standard 120/240v LED lightbulbs (how)? LED light strips? Custom designs using raw LED modules? iirc

What's the context here? Are you somehow reducing power to standard 120/240v LED lightbulbs (how)? LED light strips? Custom designs using raw LED modules? iirc (and I may not be remembering correctly), heat is what causes the degradation. Cutting power makes the LED run cooler. For personal use at home it's important to buy high quality lightbulbs for this reason. Cheap ones will cut costs on cooling and fail prematurely or experience degradation if they don't fail. Better quality bulbs will last longer with less degradation. It can be hard to evaluate what's good; lots of companies will sell you cheap crap at inflated prices. Ikea uses solid metal bases on many of their bulbs which helps with heat (they use good CRI emitters too). I suspect weight might be a good heuristic to evaluate quality. Also avoid the high power ~1600 lumen ones, it's common for them to fail early even for the higher end ones, they just make too much heat to dissipate in the standard bulb form factor. Afaik Ikea eventually discontinued their 1600lm product, probably for this reason.

convolvatron 4y ago
sorry yes, bespoke fixtures with commodity modules (mostly bridgelux - cheap and nice phosphors). as an aside, when are we going to get a usable DC power and control standard for lighting?
- kjs3 4y ago
  USB? -48v? And there's a whole ecosystem of 12v stuff under the RV umbrella. Seems like what's lacking isn't a standard (or rather the basis for a standard), but a market leader to say "we're gonna back this". But you've got way more insight than I do and I'm undoubtedly underestimating the effort.
- the_pwner224 4y ago
  Cool! Is this a commercial product that we can buy? I worked on a similar system a while ago for personal use. 300 watts of BLX COBs. Prototypes were good but they ran very hot (105 degrees) with the cooling system I had on them. Improving cooling and refining the design past the crude prototype would have made it too expensive to be practical for me, or for the market if I chose to sell it. I'm probably going to be building a new house in a few years, it'd be nice if I could run 48v wiring throughout the house with standardized connectors and control modules. The age of 120/240v with screw socket bases needs to end. But I doubt the industry will have standardized on a DC system by then. I wonder if there are any actively cooled fixtures on the market for standard lightbulbs. The common recessed in-ceiling fixtures are not great for thermals, the closed top blocks natural convection and traps hot air. A slow (silent) fan should do a lot to help with bulb longevity. I might end up doing a custom design for my house if there's nothing on the market.
  - convolvatron 4y ago
    not really. we used to sell them, but its a bit fussy. people had quite legitimate concerns about what to do when the modules went. margins are good, but not as high as fine art, and the labor is about the same for us. since our primary activity is metal sculpture....we really don't have to deal with cooling issues. 10-20 pounds of metal, even steel, makes a _really good_ heat sink, even if it is isn't optimized for maximum convection. and now your light elements are little 3cm circles a couple mm high, and you can tuck them wherever you want. it wouldn't be too hard to make you own standard. the constant current drivers often have pretty wide input ranges, especially if you can stick with simple bucks. the part where I really kinda fell down was connectors oddly enough. 3 pins, moderate current, few cycles, low cost, high contact reliabilty. anyone with better connector-fu than me have a suggestion?
    - the_pwner224 4y ago
      Just saw this other comment here. https://news.ycombinator.com/item?id=35013509 https://news.ycombinator.com/item?id=35013509 USB-C might work. USB PD supports 5a at up to 20v, looks like there's also a higher power 50v 5a spec coming up. But if you're using custom PCBs on both ends you don't really care about the PD specification, as long as you're using good quality cables you can treat the connector/cable as a dumb wire that supports sending 5 amps down a few pins. The data lines may also be useful for sending back data from the emitter module, if you had any need for that. Desktop computers use the Molex Mini-Fit Jr connector for ATX and PCIe power connectors. 6-pin PCIe power cables should be easy to source on the market, you wouldn't need to get custom cables manufactured. Those can carry ~150w. Might also be possible to cheaply source cables with just a 2 or 4 pin connector?
    - aidenn0 4y ago
      3 single Anderson Powerpole connectors (they are designed to slide together, and a drop of CA glue can make the connection permanent). Available up to 45A

convolvatron 4y ago

sorry yes, bespoke fixtures with commodity modules (mostly bridgelux - cheap and nice phosphors). as an aside, when are we going to get a usable DC power and control standard for lighting?

kjs3 4y ago
USB? -48v? And there's a whole ecosystem of 12v stuff under the RV umbrella. Seems like what's lacking isn't a standard (or rather the basis for a standard), but a market leader to say "we're gonna back this". But you've got way more insight than I do and I'm undoubtedly underestimating the effort.
the_pwner224 4y ago
Cool! Is this a commercial product that we can buy? I worked on a similar system a while ago for personal use. 300 watts of BLX COBs. Prototypes were good but they ran very hot (105 degrees) with the cooling system I had on them. Improving cooling and refining the design past the crude prototype would have made it too expensive to be practical for me, or for the market if I chose to sell it. I'm probably going to be building a new house in a few years, it'd be nice if I could run 48v wiring throughout the house with standardized connectors and control modules. The age of 120/240v with screw socket bases needs to end. But I doubt the industry will have standardized on a DC system by then. I wonder if there are any actively cooled fixtures on the market for standard lightbulbs. The common recessed in-ceiling fixtures are not great for thermals, the closed top blocks natural convection and traps hot air. A slow (silent) fan should do a lot to help with bulb longevity. I might end up doing a custom design for my house if there's nothing on the market.
- convolvatron 4y ago
  not really. we used to sell them, but its a bit fussy. people had quite legitimate concerns about what to do when the modules went. margins are good, but not as high as fine art, and the labor is about the same for us. since our primary activity is metal sculpture....we really don't have to deal with cooling issues. 10-20 pounds of metal, even steel, makes a _really good_ heat sink, even if it is isn't optimized for maximum convection. and now your light elements are little 3cm circles a couple mm high, and you can tuck them wherever you want. it wouldn't be too hard to make you own standard. the constant current drivers often have pretty wide input ranges, especially if you can stick with simple bucks. the part where I really kinda fell down was connectors oddly enough. 3 pins, moderate current, few cycles, low cost, high contact reliabilty. anyone with better connector-fu than me have a suggestion?
  - the_pwner224 4y ago
    Just saw this other comment here. https://news.ycombinator.com/item?id=35013509 https://news.ycombinator.com/item?id=35013509 USB-C might work. USB PD supports 5a at up to 20v, looks like there's also a higher power 50v 5a spec coming up. But if you're using custom PCBs on both ends you don't really care about the PD specification, as long as you're using good quality cables you can treat the connector/cable as a dumb wire that supports sending 5 amps down a few pins. The data lines may also be useful for sending back data from the emitter module, if you had any need for that. Desktop computers use the Molex Mini-Fit Jr connector for ATX and PCIe power connectors. 6-pin PCIe power cables should be easy to source on the market, you wouldn't need to get custom cables manufactured. Those can carry ~150w. Might also be possible to cheaply source cables with just a 2 or 4 pin connector?
  - aidenn0 4y ago
    3 single Anderson Powerpole connectors (they are designed to slide together, and a drop of CA glue can make the connection permanent). Available up to 45A