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Re: [ATM] Electronics help needed - temperature control

If you're as lazy as I am, you will want it automatic.
 A germanium diode or germanium transistor with the
properly-polarized amplifier after it will turn the
fan on for you.  Glue it to the back of the mirror
with some silicone.

If you really want temperature stability, we could all
pitch in and purchase Hubble from NASA just before
they abandon ship.

Kevin of Eastern Iowa
Seeker of the Darkness

--- Mark Holm <mdholm@telerama.com> wrote:

> Hey guys, you are reading too much into what I
> wrote.
> 
> By differential, I mean exactly what Don's dew
> heater circuit does:
> compare the mirror temperature to air temperature
> and control something
> based on that difference signal.  The changes from
> the dew heater are:
> 1. Power a fan instead of a heater; 2. Invert the
> control response so
> that the the fan runs faster (or just turns on) when
> the mirror is
> warmer than the air and, as the mirror approaches
> air temperature,
> either stop or slow down the fan.
> 
> Several people have built scopes with two speed fans
> already, but use
> manual control.  Also, as I noted, Alan Adler (and
> maybe Brian Greer)
> have pointed out that air temperature typically
> continues to fall during
> the night and mirrors lag.  Since it is a dynamic
> system, why not
> conquer it with feedback?  Of course, a two speed
> switch may be all the
> feedback you really need.
> 
> Mark Holm
> mdholm@telerama.com
> 
> _______________________________________________
> ATM mailing list http://www.atmlist.net/
> 


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