opto shift register

On Thu, 21 Dec 2023 21:07:14 -0800 (PST), whit3rd <whit3rd@gmail.com>
wrote:

>On Thursday, December 21, 2023 at 5:15:27?AM UTC-8, John Larkin wrote:
>> On Thu, 21 Dec 2023 06:13:42 GMT, Jan Panteltje <al...@comet.invalid>
>> wrote: 
>
>> >Thermocouples work fine too: 
>> > https://panteltje.online/pub/cryo/ 
>> >you can make your own, and the electronics that comes with it: 
>> > https://panteltje.online/panteltje/pic/th_pic/ 
>
>> How low can a thermocouple work? 
>It's not so great at the lowest temperatures; I've used gold/ 0.7%Fe versus gold
>for helium temperatures, but sensitivity is poor.   That third law of thermodynamics
>says it fails at zero.

We did a lot of helium temperature and level measurement gear for the
Supercollider in Texas. The only part that they actually built was the
helium plant.

This might be it:

https://investors.linde.com/archive/praxair/news/2006/praxair-opens-new-helium-distribution-center-in-waxahachie-texas

On a sunny day (Thu, 21 Dec 2023 05:14:23 -0800) it happened John Larkin
<jl@997PotHill.com> wrote in <lkd8oit9trsfd5punjs35ql6i51d84frvs@4ax.com>:

>On Thu, 21 Dec 2023 06:13:42 GMT, Jan Panteltje <alien@comet.invalid>
>wrote:
>
>>On a sunny day (Wed, 20 Dec 2023 17:53:13 -0800) it happened John Larkin
>><jl@997PotHill.com> wrote in <eo57oi5oooqal8g9hc60c0iq2i87mmbs4f@4ax.com>:
>>
>>>On Tue, 19 Dec 2023 07:31:03 -0800, John Larkin <jl@997PotHill.com>
>>>wrote:
>>>
>>>>On Tue, 19 Dec 2023 06:04:01 GMT, Jan Panteltje <alien@comet.invalid>
>>>>wrote:
>>>>
>>>>>On a sunny day (Mon, 18 Dec 2023 10:24:39 -0800) it happened john larkin
>>>>><jl@650pot.com> wrote in <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>:
>>>>>
>>>>>>https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
>>>>>>
>>>>>>A short low pulse shifts a 1 and a long pulse shifts a 0.
>>>>>
>>>>>What,s the use?
>>>>
>>>>One channel of an isolated temperature acquisition box. It will do
>>>>RTDs, thermocouples, IC sensors, and cryo diodes. I need several
>>>>isolated logic levels to switch ranges and such, and a multi-channel
>>>>logic isolator is big and expensive. I don't need speed.
>>>>
>>>>The alternative is to use a bunch of single-lane SSRs.
>>>>
>>>>Or maybe float a uP per channel and talk to it with one bidirectional
>>>>isolator.
>>>>
>>>>Early stages of design, many possibilities.
>>>
>>>Incidentally, cryo diodes are interesting parts. They are just
>>>well-charactized small diodes, or maybe diode-connected transistors.
>>>They act like normal diodes down to around 20K, and then "carrier
>>>freeze-out" kicks in and voltage drop goes way up as temp goes down. I
>>>think they get ohmic too.
>>>
>>>Lakeshore makes good ones. They are specified at 10 uA forward
>>>current, probably to minimize self-heating.
>>>
>>>https://www.lakeshore.com/products/categories/overview/temperature-products/cryogenic-temperature-sensors/dt-670-silicon-diodes
>>>
>>>
>>>I think transistor action stops below 20K too. I recall that jfets
>>>still work cold.
>>
>>Thermocouples work fine too:
>> https://panteltje.online/pub/cryo/
>>you can make your own, and the electronics that comes with it:
>>  https://panteltje.online/panteltje/pic/th_pic/
>>Exploring things is fun.
>
>For sure. And the physics boys often need help with electronics. You
>would think...
>
>>
>>Curiosity :-)
>>
>>and then apply it when needed!
>
>How low can a thermocouple work? Any error in the reference junction
>temp measurement is additive (or worse) and that matters near 0K. What
>did you use for the ref junction measurement? 

LM135, see the above link

>We usually use a platinum RTD working against a Susumu super-resistor.
>
>Old carbon comp resistors have been used as cryo temp sensors, but I
>think they need to be individually calibrated.
>
>Lakeshore has a bunch of exotic cryo sensors.
>
>Temperature measurement is generally nasty. I could rant about Global
>Warming instrumentation but I won't.

Na no problem here...
We have a bad NW storm, some places in the country are under water, hail thunder and LOTS of rain.
 https://nos.nl/artikel/2502459-maeslantkering-automatisch-gesloten-eerste-keer-door-hoogwater
  first time since 1997 the sea water protection door closed automaticaly here 
Hotels flooded:
 https://www.ad.nl/binnenland/hoogwater-zorgt-voor-veel-overlast-kades-en-straten-staan-blank-hotels-en-restaurants-ondergelopen~a7ab1bf4/

In article <re31oid9dqb1136cj5rctmnruvvhrm47nl@4ax.com>,
john larkin  <jl@650pot.com> wrote:
>https://www.dropbox.com/scl/fi/weo0og6siaf5ano8thng3/Opto_Shift_Reg.jpg?rlkey=g170fs3jzg6zftzrrvr3phmd4&raw=1
>
>A short low pulse shifts a 1 and a long pulse shifts a 0.

I have here a 200 led Christmas ornament. 20 m with leds separated at 10 cm.

The output is two leads, but there is button that can switch
- continuous all
- odd even alternating with odd flashing and even flashing
- od even flashing alternating with gradually dimming and increasing
- all off
- continuous even
- continuous odd
- erratically flashing.

I wonder how they do it. There is probably a ucontroller in the
tiny box. It rattles as you shake it.

Groetjes Albert
>
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