100W COB LEDs on AliExpress or Amazon

I did try pulsing some Cree white LEDs, to see how fast the phosphor was. It was as fast as I could instrument, a few ns.

A 100 watt COB LED must be blinding.

At a smaller scale, the cheap "corn lamps" have some interesting stuff inside.

High voltage PV coupler?

--

John Larkin         Highland Technology, Inc 

The cork popped merrily, and Lord Peter rose to his feet.  

"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"

Yes, you can't look at them. I added some measurements to the RIS-796 DropBox folder.

--
 Thanks, 
    - Win

Looking forward to giving this a try, Win.

I've got some lower voltage ones 10W coming that should allow comparison. They were super cheap.

Some of the really cheap ones seem to have a few dim LEDs so they're probably production fallouts. Shouldn't affect the overall performance much unless there's a systemic issue that affects the pulsed power capability like bad wirebonds.

From what I can tell the yellow phosphor has effectively zero persistence. The warm white ones have a bit of red phosphor as well, might be similar.

I have a few grams of the raw NYAG yellow 6um (extra fine grade) 545nm phosphor, by the way.

- Best regards,

--Spehro Pefhany

How do you apply a phosphor to an LED surface?

--
 Thanks, 
    - Win

Winfield Hill wrote in news: snipped-for-privacy@drn.newsguy.com:

Very carefully.

It's usually mixed into epoxy and glob-topped on the chip.

--

John Larkin         Highland Technology, Inc 

The cork popped merrily, and Lord Peter rose to his feet.  

"Bunter", he said, "I give you a toast. The triumph of Instinct over Reason"

On Friday, 10 January 2020 17:15:19 UTC, snipped-for-privacy@highlandsniptechnology.com

More likely silicone, as it is quite soft.

John

YIKES! 100 W?!? I have built 4 units, now, of a strip of 20 1W Cree LEDs on PC board material, to replace dual 48" fluorescent fixtures. I got commercial LED power supplies, they draw 21 W from the mains, using a real power meter. I'm really happy with them, they are in our kitchen, and get a HUGE amount of daily use.

Jon

It's typically compounded and mixed with dimethyl or phenyl silicone encapsulant. Epoxy is a better match for the index of refraction but too rigid for the thermal problems that come with high-power LEDs. The phenyl silicone has less of a problem from yellowing with age.

Best regards, Spehro Pefhany

P.S. The R&D kits I've seen use a two-component silicone, but apparently UV cured is also possible- but the phosphor tends to absorb the UV and re-emit it at a useless longer wavelength so it screws up the cure times.

Best regards, Spehro Pefhany

I recently bought some 50 watt flood lamps off Ali-Express. Vendors sell 1

10 volt and 220 Volt units. I ordered three 110 volt ones. And received 1 110 volt and 2 220 volt units. They are 5 leds by 10 leds and claim to be 4500 lumens. Larger and smaller ones are available. They do have so me ics side so may not be good for pulsed light. They were just under $4 each.

Dan

I bought some LED fixtures equivalent to the 48 inch shop lights that are n ot only as bright but include motion detectors so you don't need to switch them on and off. $25 at Costco. I haven't seen them in a while though. I t might be worth bugging them about to see if they will get more in.

I also bought some LED strips with about 1 LED every inch or so. I hung it over my washer/dryer and each LED created a shadow. It was a bizarre effe ct and I got rid of them. There's a reason for a diffuser.

--

  Rick C. 

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They need to be mounted on a heatsink, at least to add thermal mass. If the pulsing duty cycle is very low the heatsink can be modest, but if the pulse current increases the power dissipation by say 10x, then a 10% duty cycle will be 100 watts, and even a large heatsink will need a serious fan.

--
 Thanks, 
    - Win

The pulsed high-current approach requires bare LED stacks, without any series AC-current control ICs.

They are certainly convenient for AC offline use, but the 220V ones don't work on 110V, right?

--
 Thanks, 
    - Win

They make these now as led replacements for 4' (four foot) florescent lamp bulbs. Most likely other sizes too.

George H.

The 220 volt one that I tested had a lot of the leds produce some light, but no where normal brightness. In other words it did not work on 110v.