From: Watson 'Atto Parsec' Name
Subject: Re: Best way to power array of LEDs?
References: <0001HW.B9C26E7400A7161B165FEAC0@news.covad.net> <7tGLdeAS6fn9EwBv@jmwa.demon.co.uk> <email@example.com> <3DEE0D79.629FAC0D@boeing.com>
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Date: Sat, 7 Dec 2002 08:44:21 -0800
NNTP-Posting-Date: Sat, 07 Dec 2002 09:47:27 PST
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In article , firstname.lastname@example.org
> "Frontline Electronics" wrote in
> message news:AVdI9.46878$hK4.email@example.com...
> > The only spec I remember is distance that it can be seen from
> > but color temp may have been one.
> > Jeff
> What spec is 'distance it can be seen from'? How is this spec'd?
Yeah, kind of subjective. I've been playing around with the solar cells
I got from All Electronics, and I find out that there is a huge
difference between daylight and indoor light as far as cell output goes.
Of course I already know that this is to be expected; you won't get a
suntan from an incandescent desk lamp. But think about this. The cell
puts out, say, 3.16V and .316 mA at 1 ft from the desk lamp, which is
about 1mW. So I point the desk lamp down the street and go down this
long theoretical street 10 thousand feet, and the desk lamp can clearly
"be seen from this distance", but think about this. Using the inverse
square law, the amount of desk lamp light hitting the photocell is
10000^2 or 100 million times _less_ than at 1 ft, or something like 10
picowatts. And the eye's iris is much smaller than the photocell, so it
has much less than that. Yet the lamp can be seen clearly from this
distance, and probably much farther. So it's really quite amazing how
sensitve the eye is.
My email address is whitelisted. *All* email sent to it
goes directly to the trash unless you put NOSPAM in the
Subject: line. alondra101 hotmail.com
Don't be ripped off by the big book dealers. Go to the URL
that will give you a choice and save you money(up to half).
http://www.everybookstore.com You'll be glad you did!
Just when you thought you had all this figured out, the gov't
changed it: http://physics.nist.gov/cuu/Units/binary.html