Indeed Bob in the 70s I built a failure diagnostic equipment to record the
Idd of a chip as a function of a position of a spot of light scanning the
surface. The intensity was very low and not optimum wavelength.......it was
a scope raster demagnified by using a microscope camera accessory backwards.
The intensity was modulated and the signal detected on a PSD and displayed
on a modified Robot SSTV receiver.....but it showed just how senstive chips
are to light.
Alan
G3NYK
----- Original Message -----
From: "Bob Camp" <kb...@n1k.org>
To: "Discussion of precise time and frequency measurement"
<time-nuts@febo.com>
Sent: Monday, January 18, 2016 3:11 PM
Subject: Re: [time-nuts] Generating a solid PPS from 10Mhz source
Hi
Back in the 70’s I was involved in making LCD watches. The whole “photo”
issue had not been fully through through. One day our chief marketing guy
for
the project was driving around in Phoenix AZ. He looks down and notices
that
his watch is dead. Pops out a spare, puts it on, confirms it it working.
Hangs his arm out
the window and …. that one is dead as well.
We changed the die coat on the ASIC to an opaque version soon after that …
Light does indeed interact with semiconductors. It happens even on
circuits that
you would not *think* are photo sensitive. Physics is nasty that way ….
Bob
On Jan 18, 2016, at 6:45 AM, Poul-Henning Kamp <p...@phk.freebsd.dk>
wrote:
--------
In message <569bc23a.3030...@arcor.de>, Gerhard Hoffmann writes:
LEDs abused as References:
This is one of the most stupid ideas ever, because LEDs works both ways.
(Back when LED wrist-watches first came out, people soon discovered
that they would reset themselves when photographed with flash.)
If you insist on using LEDs as voltage references, the first thing
you need to do is to dip the LED in something which shields it 100%
from incoming light *including infrared*
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by
incompetence.
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