[kwlug-disc] OT: Below freezing cables ...

[Khalid Baheyeldin]

On Wed, Jan 9, 2019 at 9:42 PM Andrew Kohlsmith (mailing lists account) <
aklists at mixdown.ca> wrote:

> On Jan 9, 2019, at 9:03 PM, Khalid Baheyeldin <kb at 2bits.com> wrote:
> The reason I suspect bad connections is that I changed the controller to a
> backup
> board that I have. Same result. Then other RJ45 cables. Same result.
>
>
> If you can, throw the motors and mechanicals in your deep freeze for a few
> hours and then, inside where it’s warm, try to operate it.
>

Not possible. The motors are mounted inside the scope housing.

Here is how it looks like in action
<https://www.youtube.com/watch?v=tgzy1bFrGBc&list=PLZukVlnRom-3YhPkIIvXWJqaCuHc1_qj5>
(without the actual optical tube on it, or the counterweights).
The only thing that may have changed are the RJ45 cables.

Tomorrow has a high of -8C and it is dry. So may take the scope out and try
it on the patio to see if the symptoms are the same.


>
> What about the stepper drivers, are they marginally sized and higher
>> current required for stepping in cold temperatures is causing them to fault?
>>
>
> They are tiny. NEMA 11 instead of the usual NEMA 17. But they have an 18:1
> gearhead which gives them enough torque, and there are others who are using
> the same model of motors without issues (not in sub zero temperatures
> though).
>
>
> Any grease or other lubricant used in the gearboxes which may become stiff
> or become more viscous in the cold?
>

That is theoretically possible, but I doubt it. This mount is made in Japan
and they probably make sure it would work in low temperature. Also, I
bought the scope from someone in town, and probably he would have been
using it in low temperatures.


> I did buy the flat RJ45 cables and the sockets, from eBay, so they may not
> be the best
> out there.  But they are the flat ones, which are the most flexible.
>
>
> Mine come from Sayal, which I’m sure is also very poor quality. I guess if
> you had a way to perform a cable test in the cold it would make quick work
> of this theory.
>
> If it’s skipping and generally misbehaving and you go out and shove the
> cable into the socket, holding it there while retesting, does it still skip?
>

It is not practical since the scope is moving all the time (either at the
rate of earth's rotation, or faster when changing positions in the sky).

I tested the 5A power supply and it worked well (no surprise there).

Will test the same power supply out doors tomorrow.
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