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Building an LED light/flash
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mjkzz



Joined: 01 Jul 2015
Posts: 1231
Location: California/Shenzhen

PostPosted: Wed Mar 25, 2020 1:25 am    Post subject: Reply with quote

mawyatt wrote:
The heatsink is cool and looks like a car engine manifold, hot rod LED COB!!

Fans are usually a problem, here's a Godox 150watt 16,000 lumen Video Light where the fan is reported as too loud, so it's vibrating something.

https://www.bhphotovideo.com/c/product/1342001-REG/godox_sl150w_5600k_150w_led.html


Yes, the fan is definitely a problem for high magnification, the air flow, the vibration (even the quietest fan). One way is to use liquid cooled heat sink.
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mjkzz



Joined: 01 Jul 2015
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PostPosted: Wed Mar 25, 2020 1:40 am    Post subject: Reply with quote

It is so cool and not cool at same time, to work at home, so much interruptions and temptations of not doing work work Very Happy Very Happy

Did a video using that 100W LED, I am surprised that a single LED can be so powerful, even after bouncing lights, I can still get good result. No flickering . . . many part of video were shot at 24fps, I just wish I can make it one unit.

Here is the video Most of the closeup parts were shot with this LED. The "flashing" part you see on Sony Remote is not actual flash, it is how the Sony tethering software behaves. All are under continuous lights. No flashes.

I think there are a lot of LED lights on the market are like this, no flickering even for high frame rate. Just be aware that some of the LED lights are over rated (like they use 60W LED but claim 100W, or 100W LEDs but claim 200W -- this is the funny part, they claim the extra power is due to reflector effect).

The computer decided to quit on me RIGHT after this . . . in this picture, the LED is lit, lights in softbox were off.


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mawyatt



Joined: 22 Aug 2013
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Location: Clearwater

PostPosted: Wed Mar 25, 2020 7:58 am    Post subject: Reply with quote

mjkzz wrote:


I think there are a lot of LED lights on the market are like this, no flickering even for high frame rate. Just be aware that some of the LED lights are over rated (like they use 60W LED but claim 100W, or 100W LEDs but claim 200W -- this is the funny part, they claim the extra power is due to reflector effect).



A better metric for Hi Power LEDs and LED COBs is the actual optical output in lumens at a desired color temperature rather than the input power to the LED or LED COB. The efficiency of modern Cree LEDs and LED COBs ranges from ~100lumens/watt to ~150 lumens/watt from what we've found. This allows one to easily access the required optical power needed for a given setup and situation from a reference. We did a quick "hands on" test here that required 1.6 seconds exposure of a 220 lumen LED illumination for proper exposure, so for a 10ms exposure would require 35200 lumens. Here's the link and note.

"The setup is a Nikon D850 at base ISO with Mitutoyo 5X and a single 220 lumen LED (IKEA LED) undiffused as the light source. Proper exposure required ~1.6 second shutter, so this would equal a LED with 1.6*220 lumens for a proper exposure at 1 second, or 352 lumens seconds (similar to ~400 lumens). For a proper exposure at 1/10 seconds would require 3520 lumens, at 1/100s 35200 lumens, at 1/1000s 352000 lumens, 1/10000s 3520000 lumens. "

https://www.photomacrography.net/forum/viewtopic.php?t=40999&start=45

We've had good luck with Godox Strobes/Speedlights (and Adorama branded Godox) products, and even disassembled and measured various parameters to confirm the performance. From a pure electronics standpoint, they are very well designed and constructed. The previous linked Godox product has 16000 lumen output, which seems reasonable for a 150 Watt "Claimed" LED COB module (107 lumens/watt).

https://www.bhphotovideo.com/c/product/1342001-REG/godox_sl150w_5600k_150w_led.html

BTW the 220 lumen source LED mentioned is a Cree XPE rated ~100 lumen/watt with a maximum output of 307 lumens. What 100 watt LED COB did you select?
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Saul



Joined: 31 Jan 2011
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Location: Naperville, IL USA

PostPosted: Wed Mar 25, 2020 12:15 pm    Post subject: Reply with quote

mawyatt wrote:
...We did a quick "hands on" test here that required 1.6 seconds exposure of a 220 lumen LED illumination for proper exposure, so for a 10ms exposure would require 35200 lumens...

Hi Mike,
How are you measuring lumens ?
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Saul



Joined: 31 Jan 2011
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PostPosted: Wed Mar 25, 2020 12:19 pm    Post subject: Reply with quote

mjkzz wrote:
...Just be aware that some of the LED lights are over rated (like they use 60W LED but claim 100W, or 100W LEDs but claim 200W -- this is the funny part, they claim the extra power is due to reflector effect)...

Hi Peter,
Is this with Aliexpress type brands only, or well known (Cree, Osram,Philips) also ?
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mawyatt



Joined: 22 Aug 2013
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Location: Clearwater

PostPosted: Wed Mar 25, 2020 1:42 pm    Post subject: Reply with quote

Saul wrote:
mawyatt wrote:
...We did a quick "hands on" test here that required 1.6 seconds exposure of a 220 lumen LED illumination for proper exposure, so for a 10ms exposure would require 35200 lumens...

Hi Mike,
How are you measuring lumens ?


Hi Saul,

This is from the specification on the light, then somewhat confirmed by the actual LED that's used, a Cree XPE. Which has a maximum 307 lumen specification with a 122 lumen/watt maximum efficacy. The LED has a drop of 3.3 volts at 700ma, and the light power supply is rated at 4 volts 750ma. So things seem reasonable for an LED current of 550~670ma @ ~3.3 volts to produce 220 lumens.

Best,
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Saul



Joined: 31 Jan 2011
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Location: Naperville, IL USA

PostPosted: Wed Mar 25, 2020 1:58 pm    Post subject: Reply with quote

mawyatt wrote:
Saul wrote:
mawyatt wrote:
...We did a quick "hands on" test here that required 1.6 seconds exposure of a 220 lumen LED illumination for proper exposure, so for a 10ms exposure would require 35200 lumens...

Hi Mike,
How are you measuring lumens ?


Hi Saul,

This is from the specification on the light, then somewhat confirmed by the actual LED that's used, a Cree XPE. Which has a maximum 307 lumen specification with a 122 lumen/watt maximum efficacy. The LED has a drop of 3.3 volts at 700ma, and the light power supply is rated at 4 volts 750ma. So things seem reasonable for an LED current of 550~670ma @ ~3.3 volts to produce 220 lumens.

Best,

Is there some simple way to measure lm (physically), not from numbers/specs ? I saw a lot 2nd market unknown leds, mounted on the brand bases ...
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mawyatt



Joined: 22 Aug 2013
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PostPosted: Wed Mar 25, 2020 2:30 pm    Post subject: Reply with quote

Saul wrote:
mawyatt wrote:
Saul wrote:
mawyatt wrote:
...We did a quick "hands on" test here that required 1.6 seconds exposure of a 220 lumen LED illumination for proper exposure, so for a 10ms exposure would require 35200 lumens...

Hi Mike,
How are you measuring lumens ?


Hi Saul,

This is from the specification on the light, then somewhat confirmed by the actual LED that's used, a Cree XPE. Which has a maximum 307 lumen specification with a 122 lumen/watt maximum efficacy. The LED has a drop of 3.3 volts at 700ma, and the light power supply is rated at 4 volts 750ma. So things seem reasonable for an LED current of 550~670ma @ ~3.3 volts to produce 220 lumens.

Best,

Is there some simple way to measure lm (physically), not from numbers/specs ? I saw a lot 2nd market unknown leds, mounted on the brand bases ...


Don't know, I was pleasantly surprised to find the Cree XPE LED in the IKEA light. The light design is well above the cheap stuff you usually find, from the case, reflector, and the LED board is 1st class and not some cheap FR4 material, but a high thermal conductivity type, typical of the Cree COBs. I know Cree is a reputable source (was on a university advisory board with the Cree Director of RF Engineering before he retired, quality individual and company IMO).

I just measured the LED current and voltage on two lights, it's set at 500ma for both the LED modules at 4 volts. The current doesn't vary from 3.7 ~ 5 volts volts, so constant current controller built-in and not just a simple resistor limit like you would expect on a low cost light. I didn't go above ~5 volts to be save tho.

So I'm pretty confident that this is a ~220 lumen output LED light.

Best,
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Saul



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PostPosted: Wed Mar 25, 2020 2:44 pm    Post subject: Reply with quote

mawyatt wrote:
...I was pleasantly surprised to find the Cree XPE LED in the IKEA light...


Yes, but Aliexpress, Ebay etc. is different thing.
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mawyatt



Joined: 22 Aug 2013
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PostPosted: Wed Mar 25, 2020 3:32 pm    Post subject: Reply with quote

Saul wrote:
mawyatt wrote:
...I was pleasantly surprised to find the Cree XPE LED in the IKEA light...


Yes, but Aliexpress, Ebay etc. is different thing.


Totally agree, you roll the dice with things on eBay. I've never purchased anything from Aliexpress, so can't comment.

A quality distributer like DigiKey or Mouser would be a good source for Cree LEDs.

I just ordered a Godox Video LED light, the 150W 16,000 lumen version mentioned to try out and see if I like it (loud fan seems to be a reported issue). If so, then I'll order another or maybe 2. Lately I've been hampered by "the boss" about using flash, so looking into continuous lights to keep the sanity Rolling Eyes

As mentioned I've found Godox and Adorama branded Godox strobes and Speed-light products very well made and designed, so expect these LED lights to be well done. $209 for a 16,000 lumen LED seems reasonable, since the Cree 10,000 lumen COBs cost $20~40 each, then you need the heatsink, fan, controller, power supply and mounting case, not to mention putting it all together and debugging.

Best,
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mjkzz



Joined: 01 Jul 2015
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PostPosted: Thu Mar 26, 2020 3:19 pm    Post subject: Reply with quote

Saul wrote:
mjkzz wrote:
...Just be aware that some of the LED lights are over rated (like they use 60W LED but claim 100W, or 100W LEDs but claim 200W -- this is the funny part, they claim the extra power is due to reflector effect)...

Hi Peter,
Is this with Aliexpress type brands only, or well known (Cree, Osram,Philips) also ?


It is from some UNKNOWN supplier, the specs they gave me, if you call it spec sheets, are all wrong, a mess, I think I was dealing with some kids who just want to sell stuff.

But this forced me to treat it as a black box, build a model with empirical data and run with it. It turns out to be a diamond in the rough, I think I am going to build more of it for coming polarization experiments, which need a LOT OF light Very Happy
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mjkzz



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PostPosted: Thu Mar 26, 2020 9:00 pm    Post subject: Reply with quote

Early lunch . . . Very Happy

Here is a video How to measure lumen . . .

These lux meters are cheap, I have one, but I use it as relative meter, ie, I do not trust its absolute reading, but relative one -- if it says 1000 at one condition, then says 500 in another, I would be more than happy to accept that as half the scale provided I am not oerating near its max or min.

Also, if you are tinkerer and want to build your own light meter, I built one long time ago (6 or 7 years ago? geeze time flies). The sensor used is one of those for Arduino, TSM something, do not remember.

https://www.flickr.com/photos/60552763@N00/6736089499/

Or just use a light meter for photography, like Sekonic L-308S, is good enough.
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Saul



Joined: 31 Jan 2011
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PostPosted: Thu Mar 26, 2020 9:21 pm    Post subject: Reply with quote

mjkzz wrote:
...as relative meter, ie, I do not trust its absolute reading, but relative one...

Yep, correct, I'm doing like this way already, using Iphone app, and it gives pretty good idea
Quote:
...and want to build your own light meter...

No way, no time for that Smile
Quote:
Or just use a light meter for photography, like Sekonic L-308S...

In this case I have to find my Minolta meter, which is somewhere ...

Looks like, I have to stay with my Iphone app ...
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mawyatt



Joined: 22 Aug 2013
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PostPosted: Fri Mar 27, 2020 6:00 am    Post subject: Reply with quote

Saul,

I've found that any pn diode junction can be used with a DVM as a crude light meter in a pinch. LEDs work well because they have a large pn diode junction, a silicon diode like the 1N4148 also works but not as sensitive as the LEDs. I checked a few clear, red, amber, green & blue 5mm LEDs, they all worked.

Of course your camera is a light meter as you've indicated with your iPhone camera app.

Best,
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Saul



Joined: 31 Jan 2011
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PostPosted: Fri Mar 27, 2020 9:47 am    Post subject: Reply with quote

mawyatt wrote:
...pn diode junction can be used with a DVM as a crude light meter ...

Yep, during soviet occupation we had very limited electronic part supply - so , instead sensors we used Russian transistors, filed their cap tops off...it was better than photo resistors (which you couldn't get also).
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