Re: [ATM] Looking for the best PWM cycle time for dew heaters

["Don Clement" <don_clement@charter.net>]

Anthony,



My automatic dew heater controller circuit can handle the power required for
larger optics. The applications  for this circuit are quite open. YMMV. I
even use this circuit inside my toolbox to prevent condensation and rust on
precision tools. It shouldn't matter if the application is open or closed
tube. Go for it!



-Don


Anyway, I did have one question. The introduction in your document
mentions secondary's, correctors, eye pieces etc... I'm thinking of
building a Newtonian with an open truss. Do you see any issue with
warming the primary? Or were you just thinking of closed tube designs at
the time?

-Anthony

>
> Here is a DIY dew heater control that automatically keeps
> optics a small amount above ambient. PWM is not time based
> rather based on the difference of optics temperature and
> ambient temperature. This assures the minimum possible heat
> and battery power is used for minimum effect on seeing.
>
> http://www.clementfocuser.com/images/Temperature_Control_Print.pdf
>
>
>
> Don Clement
>
> Running Springs, California
>
>
>
> > Has anyone figured out the best pulse width modulation
> (PWM) time for
> > a dew heater controller?  Specifically, how long should one
> 100% cycle be?
> > If it were too long the dew heater would noticeably cool off before
> > heating up again (running at less than 100%), but is too short a
> > problem, say a few dozen cycles per second?  I was thinking
> of using a
> > PIC16F88 (yes, a 555 could do it also) and some IRF510s as
> the 12v switches.
> > Thanks.
> >
> > Allen
>
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