Re: [ATM] Electronics help needed - temperature control

["Arjan te Marvelde" <arjan.te.marvelde@hetnet.nl>]

> Would it not be better to just leave the fan on? Or is the circuit really
> meant for knowing when the initial cooldown is close enough?

OK, I see Gils' point now: the goal is to shorten the cooldown time to first
observation. This problem is independent from temperature control or keeping
away the boundary layer during observation.
You could do it with running ambient air along the mirror using a big fan,
but using cooled air obviously does a quicker job. The problem to solve:
when to stop?

Using cold air you will have to cool the mirror until the surface
temperature is below that of the outside air. How much below is a matter of
modeling the temperature distribution within the glass as a function of
time, cooling efficiency, mirror size and starting values.
You will see that more efficient cooling will lower the mirror surface
temperature faster, but will also cause a larger gradient within the glass.

To get some feeling for quantities, you can download the FlexPDE mirror
cooling model from this page:
http://home.hetnet.nl/~artm/atm/resource/resource.html
Here you will also find the link to the home of FlexPDE, where you can
download a free student version.

Arjan te Marvelde




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