DIY 250W LED Flood Light for High Speed Filming

[Mads Barnkob]

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This is part 1 of my diy led flood light that is going to be used for high speed video filming with the FPS1000HD camera.

It is being built form 5x 50W LED COBs mounted on old Pentium4 CPU coolers.

I got no affiliation with these sellers, but it is where I bought my parts:
50W LED COB chips: https://www.ebay.co.uk/itm/50-W-Watt-LED-Chip-kaltweiss-24-40-mil-4500-Lm-6000K-kw-COB-Fluter-Flutlicht/162464897645?ssPageName=STRK%3AMEBIDX%3AIT
Reflector seller1: https://www.ebay.co.uk/itm/50W-70W-100W-120W-COB-Chip-LED-Lens-Fixed-Bracket-50mm-Reflector-Collimator/112785049513?ssPageName=STRK%3AMEBIDX%3AIT
Reflector seller2: https://www.ebay.co.uk/itm/50W-70W-100W-120W-50mm-Reflector-Collimator-COB-Chip-Fixed-Bracket-LED-Lens/263468105919?ssPageName=STRK%3AMEBIDX%3AIT

[haversin]

   I wonder how this would work for a short duration flash, say one microsecond (uS) ? If driven by a 1 uS current pulse would the LED illumination last for 1 uS or would it trail off giving a longer exposure ? I have tried making an air gap flash, but the energy was too low and the flash was not very bright. An LED flash would work at much lower voltages.

[Mads Barnkob]

   I wonder how this would work for a short duration flash, say one microsecond (uS) ? If driven by a 1 uS current pulse would the LED illumination last for 1 uS or would it trail off giving a longer exposure ? I have tried making an air gap flash, but the energy was too low and the flash was not very bright. An LED flash would work at much lower voltages.

DIY LED flash is a thing and you are lucky them someone did a lot of hard work and documented it all

http://td0g.ca/2019/05/14/edgerton-a-high-speed-led-flash-diy/

[Twospoons]

Pfff. Try one of these bad boys ...
https://store.yujiintl.com/collections/high-cri-led-emitters/products/yujileds-bc-series-high-cri-cob-led-900h-1500w-pack-1pcs

120,000 lumens at a CRI of better than 95.

with a price to match, of course.

[ElectroXa]

nice setup here 

now let's build the power supply 
what topology will you use for PSU, knowing that there must be 0 ripple at the output to avoid flicker?

[Mads Barnkob]

nice setup here 

now let's build the power supply 
what topology will you use for PSU, knowing that there must be 0 ripple at the output to avoid flicker?

Something used, stable and without a doubt dangerous to the LEDs.

Server power supplies and if it all ends up in burned LEDs I will make a part 3 of 2

Ripple check, I forgot to include that in part 2, so maybe there is something for part 3, I will see if I can borrow a luxmeter somewhere as well for intensity measurements.

[Twospoons]

Any reason you chose not to run with off the shelf LED drivers? They're cheap enough, though you wouldn't want to pick on price alone.

When I built some LED lighting for my wife's art studio I spent a long time delving into the various LED offline driver chips out there, and finally concluded I might as well buy a decent OTC driver. These were 20W lamps made with YujiLED's 98CRI LED chips. Gorgeous light - noticeably different from standard LED. Very white, looks just like sunlight.

The best offline topology appears to be a 2 stage approach, with a  boost PFC followed by a constant current buck.  Most of the combined PFC+CC chips look like they have a lot of ripple in the output as a result of the crude PFC, but they're meant for consumer lighting where BOM cost is everything.

[klugesmith]

I've thought about LED-based microsecond flashlamps for a long time, and wondered about the persistence of yellow phosphor in white LEDs.
My only experiment, more than 10 years ago, indicated that persistence of that LED specimen did not exceed 1 us.

Here is a kickstarter project intended to be a commercial "microsecond" LED flash.  IIRC, it's bright white LEDs driven at 10x or 20x the nominal current.   https://www.kickstarter.com/projects/vela/vela-one-the-worlds-first-high-speed-led-flash

Xenon flashlamps have luminance far exceeding even the best LEDs.  (not the best diode lasers!).
Even the tiny flashlamps in compact digital and single-use film cameras take on the order of 100 A, at tens of volts, and their lumens per watt are not that far behind modern LEDs.

[davekni]

The white LED's I've pulsed at 0.3us didn't have a significant tail, although I was viewing them in monochrome.  Being interested in monochrome only, deep red and deep blue LEDs were more efficient, but large white LEDs are much more available and cheap, so I tested some of those too.  I've had a life-test running for the past 3 years or so of a blue LED rated for 1A continuous 2A peak, driven with 25A 0.3us pulses at ~200Hz repetition rate.  White LEDs should be similar in that respect, being made from blue and phosphor.

[Mads Barnkob]

Any reason you chose not to run with off the shelf LED drivers? They're cheap enough, though you wouldn't want to pick on price alone.

When I built some LED lighting for my wife's art studio I spent a long time delving into the various LED offline driver chips out there, and finally concluded I might as well buy a decent OTC driver. These were 20W lamps made with YujiLED's 98CRI LED chips. Gorgeous light - noticeably different from standard LED. Very white, looks just like sunlight.

The best offline topology appears to be a 2 stage approach, with a  boost PFC followed by a constant current buck.  Most of the combined PFC+CC chips look like they have a lot of ripple in the output as a result of the crude PFC, but they're meant for consumer lighting where BOM cost is everything.

Exactly the reason I went for building my own, all are designed for consumer lightning and those that are designed for high speed filming, well, I can not afford to throw money at that

[Mads Barnkob]

This is part 2 of my #diy #led flood light that is going to be used for high speed video filming with the FPS1000HD camera. It should be able to deliver around 20000-25000 Lumen.

Here I modify 3x HP server power supplies to deliver 36VDC, add fan controllers for the heat sinks and box it all up in a "very compact" box that can be handheld.

[Mads Barnkob]

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This is part 3 of my DIY LED flood light that is going to be used for high speed video filming with the FPS1000HD camera.

In this video the lux value is measured to 25000 at 1 square meter which corresponds to the given lumen value for the LED COBs.

The 36VDC power supply ripple is examined, the 50 Hz ripple is limited to around 1VDC and the high frequency 20-45 kHz switching noise is no apparent problem.

There is some flicker in the background when recording at 1000 and 4000 FPS, but once it gets up to 8000 and 20000 FPS, there is not enough light to even get the subject properly lit up.