New Part Day: A fake Sun

LED technology has improved by leaps and bounds in recent years, with what was once considered unachievable being common place now. Two of the main parameters of interest, total input power and conversion efficiency have been steadily increasing over the years. An efficacy of 120 lumens/watt is fairly common nowadays, and it may not be improbable to expect double this figure in the near future. Input power ratings have also steadily increased, with single LED units capable of 100 W or more becoming common.

But the Chinese manufacturer Yuji seems to have hit the ball out of the park by introducing their BC-Series, 500 W, high CRI, high Power, COB LED. Single, 500 W COB LED’s are not new and have been available since a couple of years, but their emitting surface areas are quite large. For example, a typical eBay search throws up parts such as this one – 500 W, high Power LED, 60,000 lm, 6000-6500K. It has a large, square emitting area of 47.6 x 47.6 mm. By comparison, the Yuji BC-Series are 27 mm square, with an active emitting area only 19 mm in diameter. This small emitting area makes it easier to design efficient reflector and/or lens units for the LED.

Luminous Flux is between 18,000 to 21,000 for a color temperature of 3200 K, and between 20,000 to 24,000 for the 5600 K type. Further, this high power rating is accompanied with a pretty high color rendering index (CRI) above 95. This allows the LED to faithfully reveal the natural colors of objects due to its wide spectrum. Electrically, it is rated for 12 Amps with input voltage between 35 V to 39 V. This translates to between 420 W ~ 468 W of input electrical power. Some quick math tells us that the efficacy efficiency works out to just a little over 50 lm/W, which isn’t all that great. But with light sources, you can have high-efficacy high-efficiency or high CRI, but not both – that’s just how the physics of it works.

At US $ 500 a pop, these eye blinders do not come cheap and may not find much use for individual hackers. But for some applications, such as studio and theatre lighting or photography, they may be just what the Doctor prescribed. In the video after the break, you can see [Matt] from DIY Perks give a rundown of the LED’s features and take it for a test ride.

49 thoughts on “New Part Day: A fake Sun

  1. Something tells me that the $500 retail price will clearly not likely remain that high for long. My bigger question though is how does cooling have to be handled when you put that much power in such a small surface area? LED lights certainly have to be cooled differently than, say, an incandescent light bulb, which generates radiated heat.

    1. I use PC processor cooling block on my 100W LED, I run the fan from 5V (instead of 12V) to slow it down without using PWM. So 500W LED will probably work fine with same cooling, but fan will have to be run at greater speed.

  2. The main problem with these high output LEDs is dealing with the heat density of the package. Although it may sound like it is a good thing to have a smaller-ish package the issue will be removing the heat generated by the LED in such a small surface area (heat dramatically impacts LED lifetimes). As an example, 5000 Lumen Cree COB Leds can generate temps of about 70C with a surface temp of 135C … and that is considered “normal”… I can only imagine what the temps are for a single 20000 Lumen COB LED would be… gulp…

      1. @Digital Corpus,
        You are quite right… When I design with these LEDs I keep the temps as low as possible and 70C is my limit. My other designs using more of the smaller lumen output LEDs operate at 33C. As you are no doubt aware, operating at lower temps extend the rated LED lifetimes dramatically… way past the 50K or 100K hours that are marketed.

        1. And affect their luminous efficacy and CCT too. Though here in the climate I’m in, we hit 41 °C in summer so I’d be aiming for a 10 °C delta above ambient on my end for the lower power stuff.

    1. I always get a little queasy when I notice one of my precious machines is running at a temperature that would cook me, but I have to remind myself that certain gizmos are comfy at those levels. I’ve known multiple people who got extra heat monitoring equipment for their motorcycle engines, only to become paranoid and over-cool them to the point of wearing them out, having inadequate mechanical tolerances from lack of thermal expansion. If it’s designed to run that way, hot is good.

  3. you say “by comparison” and then compare an edge dimension to surface area… not terribly useful. i would suggest instead ~2260 square mm *compared* to ~280 square mm. that’s a meaningful comparison. almost a 90% reduction in surface area, which is pretty impressive!

  4. Now this is a step closer to relamping older digital projectors and rear projection TVs with LEDs. Bring the cost down under $100 and it’ll be worth it. Now if only I could figure out how to hack my Toshiba TLP-771 for an LED. The price for a replacement bulb is insane! I don’t care that it was originally a $10,000 projector, I picked it up used for $10.00. Works great, for things that don’t need more than 1024×768 through an analog VGA connection. The overhead projector camera is also a nifty thing, but not for transparencies.

    1. That was at least 10 times more interesting then a super small super expensive and un-hackable LED. That (in order to operate) requires a larger cooling system then my motor cycle and uses and requires the airflow of a something sounding like a vacuum cleaner. Tell me, how is this going to help me with my projects, what do I learn from it. It’s like a video of a supercar, sure they are cool, sure they are fast, sure they have interesting technology… but me using it is very unrealistic. Therefore The video of the arc light is much more interesting, it gives you a view of the past, it learns you that in the good old days people could do a hell of a lot with elbow grease, brainpower and ingenuity.
      Thanks for posting the arc light video.

      1. You really think that, back in their day, an arc light wouldn’t have been way more expensive and difficult to acquire? Or that if you managed to get your hands on a setup, you could do *ANY* hacking with it? Or even turn it on? If you think you could hack anything that takes a thousand-amp current, you’re too stupid to be working with electricity. Even after going through the grid, that’s over seventy thousand watts of power, and double-aught (2/0) wire is just under 3/8th of an inch (9.2mm) in diameter, making thick enough to be useful for beating back the morons who think they can mess with anything that requires 2/0 cable. And assuming you could even find an old carbon arc lamp (because yes, there are more varieties than just carbon), it would probably have been disassembled and retrofitted for a more modern light source, and even then they’re well over $1000USD.

        Now, on the other hand, we have a sleek, shiny LED with a big freaking heatsink and requiring a pretty beefy power setup. While to you it may seem blasé or passé or just some small iteration in the forever forward-marching progress of technology, let me tell you, this thing is a flippin’ miracle. It’s a godsend. It’s exactly, exactly what the professional lighting industry has been needing to make proper LED lighting fixtures for stage, film, and photography. You see, as was touched on a little in the video and article, LEDs generally have a very narrow wavelength range for light output, and only fairly recently have been able to put out enough light to even begin to compete with the standard lighting sources in the professional world – for my comparisons, I’m using the 575 watt HPL lamp from Oshio, which is pretty standard for a lot of stage lights these days, and with which I’m exceedingly familiar in terms of general light output and color response.

        This gem of an LED puts out 18,000 lumens at about 450 watts with a CRI above 95 and a color temperature of 3200 degrees. The HPL puts out 16,500 lumens at about 575 watts with a CRI of 100 (which is the max) and a color temperature of 3200 degrees. An FEL lamp from Impact puts out 27,500 lumens at 1000 watts with a CRI also of 100 (both the FEL and HPL are tungsten halogen lamps) and a color temperature of 3250 degrees.

        From those numbers, the only thing lacking in the LED is color response, which, at least in very recent years, has been the only thing holding back professional LED lighting fixtures. A few companies, particularly ETC, have released products which attempt to overcome the issue by mixing a bunch of different colors of LED and then calibrating the emitter assembly to match the venerable HPL, but it still ends up being mountainous – that is to say, peaks at the frequencies of the LEDs and valleys everywhere else. But with this, with a few years more development to help get the thermal characteristics and price a bit more manageable, we might finally get the holy grail of professional LED lighting technology.

        You, you ask, does any of this matter? $$$$$$$$$$$$$$. Lots and lots and lots of money. LOTS of money. So much money.

        I work in a theater. We put on plays, which means we have to light the stage, as much for effect as for actually being able to see what’s going on. It’s a great time, lots of fun, plenty of neat toys like the 192 individually-addressed lighting circuits at 1200w/120v whose dimming is controlled through pulse-width modulation with a zero-crossing trigger.

        At any given time, we have about 150 fixtures hung and plugged in, drawing power as we need them to. Most of these use 575w HPLs, but a few use 1kw something-or-other lamps for when we need to paint a whole lot of colored light against our white backdrop which we will call 575w for the sake of simplicity. Now, we rarely have all of the lights on at the same time, and rarely use anything higher than 50% of their max brightness, so let’s say 100 (fixtures) * 285w (50%) = 28,500 watts as an average continuous draw over a four-hour period (preshow, run of show, and postshow, all of which have the stage be lit).

        Now, I live in a place where electricity is relatively inexpensive at 6.8 cents per kilowatt-hour for the first 1000 kWh, and 7.5 cents after that. Over the course of a single night, we use 114,000 watts of power. That works out to be about $8500/night.


        Let’s replace those 575w HPLs with 450w LEDs. Because of the difference in lumens, we can actually run the LEDs at 90% before any other calculations, which means we can count it as a 400w light source. Redoing the math, that gets us right at $6000/night.



        If you think that a carbon arc lamp is more interesting than a high-efficiency, high-CRI LED with high output lumens, then you clearly have no idea what’s going on in the world outside your tiny set of interests. Don’t go dragging on something just because it’s not for you. Frankly, if you’re not at least interested in this, you’re not interesting enough to be an arbiter of what’s HaD-worthy.

        1. Cool, that’s an unexpected (To me, but I never thought about it.) spinoff, in a couple of years time, community theatre will be getting wayyy more popular again, because it’s suddenly a third the cost to turn the lights on.

        2. >”That works out to be about $8500/night.”

          114,000 kWh a night (6 hours?) would imply your stage lighting consumes 19 Megawatts. Now that’s a heck of a lot of lamps. At 575 Watts each, you’d have 33,000 lamps burning. Your math is way off.

          >let’s say 100 (fixtures) * 285w (50%) = 28,500 watts as an average continuous draw over a four-hour period

          28.5 kW over a 4 hour period is 114 kWh, not 114,000 kWh. Your power bill is indeed about $8.50 and NOT $8,500

        3. I find it strange that you seem quite knowledgeable about the specs of the lights, but didn’t stop to check math after coming up with such insanely huge numbers. 28.5KW is not that much. It’s $8.5/night, not $8500.

    1. Um… there are better light sources then a LED for light therapy. In fact, a main issue with LEDs (from a human factors perspective) is, that the spectral output is *very* different from that of the sun. Unfortunately, most proponents of domestic LED lighting have very little knowledge about what a good light source’s spectrum should look like and happily suggest the use of LEDs with very little output in the red spectrum. Even worse, by striving for “efficiency” those LEDs also emit almost no IR (infrared) – but a whopping amount of blue and even some UV. … the latter aspect has led to a recent publication from Australia (the first country to ban traditional light bulbs) where there is now solid evidence that the spectra of CFL and LED light sources are a factor that is leading increasingly to eye damage in the general population (thus confirming earlier studies from China with animals).

      But back to the S.A.D. of your wife: Obviously, you sort of need to replace the sun (broad and smooth spectrum) AND you want lots of lumens. This guy already built such a device using a HID light source:

      A few things to keep in mind when using such a device: first, look at the spectrum of the lamp you want to use. Use “daylight” (like type 942), not warm-tone. 1) Pay attention to the orientation of the bulb! Not all bulbs can be used in any orientation, some will fail very early when used upside-down etc. 2) Verify that UV radiation is sufficiently blocked – either by the glass envelope of the bulb or by a filter glass 3) never use the bulb w/o an additional glass that will hold back shards in the event of a bulb failure 4) ensure sufficient ventilation of the bulb 5) be aware that the line from the “ballast” to the bulb needs to handle up to 6000V – so you need to use a short lead and make sure you get the type with double insulation 6) when buying used HID fixtures, make sure you go for an electronic ballast (not the heavy transformer type) and once you are happy with the thing replace any old bulbs for a new one (old ones blow up more often). Good luck!

      BTW: I don’t officially suffer from SAD but I have a circuit with HID lights in my workshop – when I switch them on I almost immediately feel more happy, focused and energetic …

    1. A CRI of 90 is actually not very impressive … ok for a parking lot but not desirable for a retail situation or even a domestic environment. Also, “CRI” is not a very good description of how “natural” (i.e. sun-like) a light source’s color rendition will be in real-life,,,

  5. ” 114,000 watts of power.” is 114kW. Lets’ say a production uses the lights for 4 hours, that’s 456 kW hours. At 7.5c per hW hour, my calculator gives… $34.20.

    Someone needs tio check their math. No one spends $8500/night on power.

    chris watts

    PS I work in film, and I do agree with the poster’s main point- this little thing will be huge,.

  6. > Chinese manufacturer Yuji

    Unless California has recently fallen into the sea and drifted 7000 miles west, Yuji is a US company. They are based in Sunnyvale, just a couple of blocks from the original Fry’s location.

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