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Comment by lightedman | Hacker News Reader

GE has been busted by myself falsely advertising their UV LED bulbs. In fact, I'm currently looking for more people that bought these A19-style UV Black Light bulbs from GE so we can start a class-action suit for false advertising and unfair competition.

In short, I wouldn't trust GE for LEDs. In fact, I'm so disillusioned with almost every company out there (Cree, Philips, GE, Sylvania) that I've simply gone back to building my own lights for my specific purposes. I can't trust any of these companies to be accurate or truthful in their marketing.

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> that I've simply gone back to building my own lights for my specific purposes.

Is this what your username references?

Yup. I design my own LED units, have a company called SinkPAD (I think it's Adura, now) make the boards, then I populate the boards myself.

Maybe you could point me in the right direction. I'm looking to construct a panel that can make it look like day, but has infinite dimming.

Making daylight is easy enough. The Nichia 219B LED in 5000K R9050 (CRI 90+, R9 50+) is beautiful. 12-18 of them will comfortably make over 5000 lumens without having to be driven especially hard. It's not terribly hard to come up with options to wire them up and heatsink them properly either.

What I haven't been able to find is a suitable power supply and driver. I want to plug it in to 100-240V and have a dimmer knob giving me 5-5000+ lumens via current regulation, not PWM, though very fast (> 10kHz) PWM might be acceptable. Yes, I'm aware the tint will shift a bit through the brightness range without PWM. I'm OK with that.

"I'm looking to construct a panel that can make it look like day, but has infinite dimming."

Infinite? Not happening, but if you want to get CLOSE, your best bet is in a simple benchtop voltage and current regulator. I use four Nichia 219B LEDs to light my 55-gallon aquarium, are you SURE you really need 5,000 lumens? You could probably get away with just four of those, a fixed 12V power supply with adjustable current, and be done with it, they're ungodly bright and a quad of those can match up with the Cree MK-R.

It need not be truly infinite or stepless as long as it has hundreds of steps. I want to dial in the ideal level, rather than pick from say... 10 options.

I'm sure I want over 5000 lumens. When I want my room well-lit to promote a sense of alertness and compensate for shorter days in winter, my best current option is a flashlight that produces about 4200 lumens bounced off the ceiling. No, that's not one of those BS marketing numbers: the light is a Jetbeam T6, which in stock form uses four Cree XP-Ls powered from four 18650 Li-ion batteries. Independent tests, including my own have found its claimed performance to be accurate. I swapped the XP-Ls for Nichia 219Cs (5000K, CRI 80+, R9 unspecified) and measured about a 2% loss of output, but increased intensity. This works as a room light, but requires an external cooling fan to run on high for longer than about 10 minutes (it has a thermal sensor and stepdown), and the batteries can only keep up with that output for a bit over an hour. 219Cs are more efficient than 219Bs and can be driven much harder, but aren't as pretty. Even the recently-released R9050 (CRI: 90+, R9: 50+) version just doesn't look as nice to me.

Four 219Bs definitely can't produce 5000 lumens. The 90+ CRI versions peak at about 600[0], but I don't want to run them at peak output; the harder they're driven, the stronger the spectral peak of the underlying blue LED. I want to run them at about 300lm/ea. 12 of them will get me that, but I'd actually rather have more than 5000 lumens.

Thanks for responding. I was hoping for an off the shelf driver, but it looks like I'm going to be improvising a bit more.

[0] http://budgetlightforum.com/node/27652

Here's an idea. Get a single 50w COB LED that can match or get close to the Nichia (they exist, I'm sure of it.) Actually, Nichia has some of their own that do match - http://www.nichia.co.jp/en/product/led_product_data.html?typ... and http://www.nichia.co.jp/en/product/led_product_data.html?typ.... Then you just need a simple heat sink, and fixed voltage power supply with adjustable current. Those aren't too expensive, but you're still looking at roughly ~$80 in total BOM.

I thought about getting one of those bigger arrays, but I'm concerned that the light they produce may not be as pretty as the 219B even if they have the same color temperature and CRI on paper. The 219C, for example is not, though it's still very nice and capable of quite a bit more output. Output per emitter and overall efficiency aren't major concerns for me: we're talking about around 90W for 6300lm driving 18 219Bs at 1500mA each.

It's also difficult to find the 048Z available in single quantities. I didn't find the R9050 version on Octopart, Other versions cost $50-60, while 219Bs in several tints are readily available from suppliers of DIY flashlight parts for $3/pc. Getting 219Bs and triple or quad copper MCPCBs is easy, and they can be configured for any multiple of about 3 volts, while the 048Z requires a 50 volt power supply.

I was expecting to spend over $100 when all is said and done.

"It's also difficult to find the 048Z available in single quantities"

Just ask Nichia for an engineering sample. :) Boom, free sample if they've got one for you to utilize. I don't know how many Cree, KingBright, Nichia, Osram, and Epistar LEDs I've got just because I ask to test them.

As for the 50V power supply, it'll run on a 48V 1.25A driver. You'll be fine and those are about $20 each.

I have hundreds of dollars worth of flashlights I got by offering to write reviews, but asking for an engineering sample never crossed my mind. I may have to try that.

If you point out to them reviews you've written (some of them mentioning their LEDs favorably) you'll get the engineering sample no problem, I imagine. They like people that promote their products and bend over backwards to get them tiny things that cost them far less than what they're going to get in potential advertising.

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