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From: grege@gold.GVG.TEK.COM (Greg Ebert)
Newsgroups: sci.electronics
Subject: Re: LED refresh rate
Message-ID: <1057@gold.GVG.TEK.COM>
Date: 6 Jun 90 16:34:59 GMT
References: <30513@cup.portal.com> <61580@sgi.sgi.com> <30550@cup.portal.com>
Distribution: usa
Organization: Grass Valley Group, Grass Valley, CA
Lines: 17

>--+---------------
>--| Can someone tell me what is the average time for a LED to fully lit
>--| and vice-versa?  I remember it is around 3Khz or was it 300Khz?
>--+---------------
>--
> 
>     Ooops, I should make that clearer.  I want the refresh rate for LED
>that a human eyes can tell between an OFF and ON cycle.  Heck, for 
>1mhz or faster, LED will just fully lit to the human eyes

	I used 100Hz, but you can go down to 50Hz. Watch the duty cycle vs.
	current - at lower duty cycles you need to increase the current to
	obtain the same luminous output. I built a multiplexed 10-digit
	display, thus each digit has a 10% duty cycle. I got decent
	brightness at 2.5ma/segment at DC, so I ran 25ma/segment during
	multiplex operation. By the way, when I say '100Hz' refresh rate
	with 10 digits, I am switching at 10*100Hz = 1Kz.