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

[Don Clement]

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