[time-nuts] High accuracy temp controller ckt

[Dr. David Kirkby]

On Fri, 12 Jul 2019 at 22:02, Hal Murray <hmurray at megapathdsl.net> wrote:

>
> drkirkby at kirkbymicrowave.co.uk said:
> > If it could run from a few NiMH cells for 48 hours, that would give the
> > option of shipping it. I don't know if that's going over the top, but it
> > would be an interesting exercise.
>
> Shipping a TEC cooler could get interesting.  You need to get rid of the
> heat
> somehow.  Cooling fins on a package would be interesting.


That is why I said that I would avoid a TEC. Running an oven should be less
problematic.

>
>
> The airlines don't like dry ice.  You could try an ice pack/gel.  If it's
> well
> insulated, the TEC will be off.  The heater won't take much power.  It's
> just
> a matter of how much insulation you need.


I would not aim to ship by air, although at a push that might be possible.

In the UK, in theory items can be shipped with batteries by Royal Mail
subject to some restrictions. Batteries  inside equipment are okay up to
some capacity. Damaged cells or lose cells are not. In practice a lot of
staff in post office shops say no to batteries.

I regularly get alkaline and NiMH batteries delivered from Farnel by UPS.
The packages are not marked. In contrast, even a coil cell comes in a box
saying it is batteries, not in transport if the package is damaged etc. So
Farnell follow all the rules.

I contacted DHL once about a UK shipment of a battery powered item. That
was not a problem.

If the box was much bigger than an OCXO, resistor oven, I don’t believe
heat would be a problem.

>
>
> What's the hysteresis on a resistor?  Is it really important to ship it
> powered up?


That I don’t know, but sometimes one does things as a challenge out of
interest, and to learn. It would be interesting to know if a resistor was
worth shipping powered up.

Dave.
-- 
Dr. David Kirkby,