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You'll immediately know if you have one of these new breed of LEDs as soon as you pick it up. They feel very "sharp" and lightweight.
Apart from saving money, I'm not sure why these rather flimsy things exist. They look like a 50W LED with 5 rows of 10 chips, but they are very thin and light. I think they may be a way to make a floodlight look like a 50W one but with a smaller driver.
One interesting feature is that the connection tabs are actually in line with the LED rows. So the + and - marks are actually next to their corresponding terminals.
And even with tiny little LED chips with single bonds, the LED was very leaky in terms of the parallel resistance effect across each row.
You'll immediately know if you have one of these new breed of LEDs as soon as you pick it up. They feel very "sharp" and lightweight.
Apart from saving money, I'm not sure why these rather flimsy things exist. They look like a 50W LED with 5 rows of 10 chips, but they are very thin and light. I think they may be a way to make a floodlight look like a 50W one but with a smaller driver.
One interesting feature is that the connection tabs are actually in line with the LED rows. So the + and - marks are actually next to their corresponding terminals.
And even with tiny little LED chips with single bonds, the LED was very leaky in terms of the parallel resistance effect across each row.
try the new Cree cxa/cxb 3070 . They produce twice the light of the old type square one's and run so much cooler. A cheaper alternative are the Citizen Clu 48 which match the Cree's for a lot less £or$
Can you recommend a good 50W chip led then please Clive? Thanks
Hi, have you used Yuji LEDs??
I've got a very bare knowledge of the LED, but I am aware that these need a resistor to limit the current. Is it OK to safely connect 50W LED as presented above, atraight to the car battery (heatsink will be installed)? I am looking for cheap but effective battery powered light in a garage.
please make video how to distinguish between these from outside or pictures, maybe the steel tray is shaped slightly different
have you tried powering them with 25 or 50w? did they all light up? i had 10w led but all 9 leds didnt light up until i got to 6-7w
I have just received a 100watt led from eBay and I am doing the low voltage test and to my surprise, they all lit up at the same time!! There is only one single led that lights slightly late. But 99 chips in there all light up! I was amazed! I wish you could send pictures on comments.
Are these actually 25 and 50 watt LEDS, or equal output to a 25 and 50 watt incandescent bulb?
One purpose could be to use a now-somewhat-standard package size, in an application where you only need a 25W LED and along with that, the lower thermal density means you should be able to get away with using a heatsink less than half the size "IF" all else were equal – which is seldom the case, and personally I'd rather under-drive a 50W LED at 25W, but suppose that after cutting a silcon wafer they have a bunch of smaller chip (areas) left over. This would allow maximizing yield from the wafer.
Running the chip at such low voltage/current that most have nearly no forward current is indeed not the greatest way to test them due to how non-linear the voltage-current curve is at low current. I would look for uniformity at somewhere between a tenth to half of its "rated" power for something hopefully more representative of real-world usefulness. You may need a camera with 1/6400s shutter speed at -3eV exposure to analyze it though, depending on how bright it gets.
What is the current before the global 'knee' where they all turn on? I guess to a large degree, you only care about lm/W if using them at maximum, or PWM.
The remaining interesting question would be do the 'leaky' LED chips get more leaky with time, perhaps to the degree they start causing current hogging and overheating of 'good' dies.
A large '25W' LED at least is much, much easier to interface thermally.
I don't think either of these LEDs are "proper" compared to something like a Cree CXA or CXB… They may be fine for experimenting with or lighting a home, but I would never use them for anything mission-critical like headlights on a car.
While recently visiting Los Altos (California), I found it interesting that most street lights and traffic lights are LED now. The obvious tell-tale sign is that I can clearly see rectangular matrix of white dots, similar to a large LED light used for videography. Even large streets such as 4-lane motorways have LED lights are surprisingly effective at lighting the street, especially when compared to HPS lighting where streets using HPS lighting merge.
Despite the widespread use of LED lighting there, I have seen very few floodlights there that use this these COB type LEDs and certainly not with any street lights, probably because they produce harsher lighting than having individual LEDs spread out across a panel. Most shops and parking lots there use LED tubes in place of fluorescent tubes. One obvious flaw I noticed with the LED panels is that I saw the odd light with one or more clusters of LEDs out, especially traffic lights where I seen some with several clusters out within the circle. They also seem to upgrade the traffic lights as the bulbs fail as there were many traffic lights where the yellow light is clearly incandescent and a few where either the green was incandescent and the red being LED and vice versa.
Hey Clive!
These LEDs have usually not aluminum plates, but copper or brass (for the cheap or low power ones) baseplates.
I would say find a minor use for it and see how long it lasts, as its a cheapy jobbie it may last a week lol 😀
When do we get more clown science?