[time-nuts] Generating a solid PPS from 10Mhz source

Magnus Danielson magnus at rubidium.dyndns.org
Mon Jan 18 17:26:00 EST 2016


Hi,

No, the black plastic around ICs isn't black by chance.
Einstein got his Nobel price on the photoelectric effect, which is 
relevant in this case.

A few years ago I assisted in modifying a camera for an amateur 
astronomer. Among the modifications, one was to turn of power for a 
pre-amplifier, as the biased amplifier was also emitting a faint 
infrared light that the sensor picked up and accumulated causing a 
redish gradient over the whole screen - mathcing the radiation pattern 
from the on-chip amplifier. By only powering on the amplifier before 
read-out significantly reduced the effect to essentially zero.

Cheers,
Magnus

On 01/18/2016 04:11 PM, Bob Camp wrote:
> 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 <phk at phk.freebsd.dk> wrote:
>>
>> --------
>> In message <569BC23A.3030400 at 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
>> phk at 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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