Re: Electronic Banner
From: Jonathan Kirwan (jkirwan_at_easystreet.com)
Date: 08/30/04
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Date: Mon, 30 Aug 2004 22:30:02 GMT
On Mon, 30 Aug 2004 20:30:02 GMT, John Miller <me@privacy.net> wrote:
>Josue Hernandez wrote:
>> I was wondering if anybody out there can help me by finding a
>> schematic of an electronic banner? I am traying to build it from
>> scratch?
>
>The hard part (in doing it right) is getting ten times the LEDs you need,
>then lighting them all up and sorting them into 10 matching sets.
>
>As part of a a scrolling sign project, my work group once got a tour of the
>factory of an OEM we were considering, and got to see the brightness/color
>matching room. Instead of the robots you might expect, they employed women
>with particularly good visual discrimination, gazing at LED-covered panels
>on the wall. Mind-boggling.
I developed systems for Infineon (when they still owned their optoelectronics
division) to automatically sort and bin on both hue and intensity, in accordance
with how humans would usually observe them. (Both for single LED dice and for
tri-color assemblies.) The resulting systems were more repeatable than the
original standards equipment they'd used to judge these machines, originally,
and they made their measurements in a 1/100th the time, as well. I'm a little
bit proud of the quality of the resulting instruments.
I'd imagined before this project that LED fabrication was precise enough that at
least where they are all cut from a single wafer one could expect them all to
perform similarly. At least from the point of view of a human viewer -- but no,
apparently not so. Processes just aren't that good and they *do* need to be
tested and graded, if you don't want hokey-looking displays as a result. It's
not so important to use the same hue and intensity LEDs on all production
displays, but it is often important to use all with the same hue and intensity
for LEDs that are part of an integrated display on a given unit.
Women do have a demonstrated better capability at color gradation -- a finer
sense. There's a large testing kit that used to be used to qualify "color
checkers" (and may still be used, at places where humans are still used in that
function) who analyze color prints as they roll off the printer. (My wife used
to do this and could color check three rolls simultaneously, as they came off
the printer without making mistakes [periodically, they'd verify her work by
doing a post-mortem on a roll, at random.]) I've never heard of a case where a
man passed the test satisfactorily.
(Today, my wife can still spot almost anything that is out of place in a scene.
When we are driving down a road, she'll notice some odd, tiny bird in the woods
we are passing -- something that I couldn't easily notice if we were dead
stopped and I spent some time trying hard. It's a refined skill, I guess.)
I don't know whether this is genetic (I'd always assumed it was) or a matter of
very early training due to differences in activities thrust upon infants (just
saw the results of a new science report appearing to demonstrate that color
discrimination can be severely impaired by raising young in environments that
are drab and that this acquired learning difficulty cannot be easily remedied by
years of additional training afterwards.)
Your comment reminded me of the time that Feynman talked about, when he managed
a room full of women 'calculators' for the WW II bomb project in the US. But
like the fact that modern computers do that work both faster and more precisely,
so can color and intensity binning equipment do the job of rooms full of women
and do it as well and certainly faster, too.
Jon
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