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Re: LED clculators not working..

Posted: Tue Mar 22, 2016 8:30 am
by dacflyer
well i was running mine less than it should be, so that the brightness matched the other led display i have. ( mixed leds displays from junk box )

Re: LED clculators not working..

Posted: Tue Mar 22, 2016 9:36 pm
by haklesup
First, I agree, the current source is overkill but I was impressed with the low cost and wide selection range

"1Ma is not even close for typical LED (maybe in closet at midnight during a power outage)"

I took your word at first then I did I digikey parameter search to see if you were right. What I found surprised me in the huge range one can purchase indicator LEDs (well, it shouldn't surprise me given the range of applications, nothing is typical). While 10mA to 20mA, 2V is often common, there were plenty of 1mA and 2mA 1,85V LED with decent brightness of 400mcd to 500mcd red and orange, brightest was a whopping 3000mcd green and 1600mcd blue (probably keychain lights).

OK I don't have a good sense of how bright mcd is but 10mA LED have similar range of dim (less than 1 mcd) to bright LEDs

ya, 5-2/220=0.0136 or round to 14mA but the 2V Vf is not precise so the calculation may be off a bit.

That's not to say this applies to the display, appears that's resolved at 10mA give or take for brightness preference