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Old 03-01-2019, 10:04 AM   #1
capwizard
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Default LED current

LED 3535, Lumens 85lm, Current 300mA, Voltage Up to 19V

I have a question when we going to buy LEDs they say 300 mA is that means at 85 luminance condition.

we know LED can go very low and up to 800 mA for short time. So, what is the factor that determines LED marks current?
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Old 03-01-2019, 11:06 AM   #2
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Default Re: LED current

"marks current"? or do you mean maximum current?

Lots of things, but maximum current is determined by how much heat the die/wirebond can deal with before melting down. There is a heat capacity of the die and wire, so short (milliseconds), high current pulses can be tolerated as long as there's enough off time to let the heat generated dissipate. Thermal resistance dictates how much off time is needed, and there are portions of the die that have higher thermal resistance than the side contacting the heatsink.
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Old 03-01-2019, 11:46 AM   #3
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Default Re: LED current

Yes...Max. Reverse Current 350MA but how can I test it?

this is for my next project is for an unknown LED I can test the maximum forward current and luminance then sorting and reclaim used leds.

Maybe I can use my own standards. I put 100 mA to the LED see how much luminance come out and use this to sort all the LEDs.
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Old 03-01-2019, 12:25 PM   #4
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Default Re: LED current

Quote:
Originally Posted by capwizard View Post
LED 3535, Lumens 85lm, Current 300mA, Voltage Up to 19V

I have a question when we going to buy LEDs they say 300 mA is that means at 85 luminance condition.

we know LED can go very low and up to 800 mA for short time. So, what is the factor that determines LED marks current?
Do you have full spec sheet?
I.E. see page 4. http://www1.futureelectronics.com/do.../MXL8-PW65.pdf

http://www.giangrandi.ch/optics/lmcdcalc/lmcdcalc.shtml
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Old 03-01-2019, 03:47 PM   #5
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Default Re: LED current

the manufacturer used 100 mA current to test leds.

the beamwidth (beam divergence) 2θ, which is the angle of the cone of light emitted, we can do an approximate calculation

In fact, my next question is how to test leds with diffusion lens? It is already written in the article and taught me how to calculate luminance.
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Old 03-01-2019, 05:32 PM   #6
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Default Re: LED current

it's all about disipating the heat - like any semiconductor.
however, there is little point taking the piss with it because the current to lumens curve levels off fast near the top.
doubling the current may only give you an extra 20% lumens - the rest is more heat.
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