Re: [ATM] Electronics help needed - temperature control

["Don Clement" <clement.focuser@verizon.net>]

Mark,



I suggest a simple solution using my differential circuit to control speed
or number of fans blowing across the front of the mirror homogenizing the
boundary layer: Switch the sensors use D2 for ambient and D1 for optics.
Parsimony.



Don Clement

Running Springs, California


> 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.

_______________________________________________
ATM mailing list http://www.atmlist.net/