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Arduino Based
Bob,
I have already built all of my dew heater straps with an integral LM335 - before I new of the Arduino and the 1 wire temperature sensors. If I stay with the LM335, to keep ports free on the Arduino, I am thinking of multiplexing the inputs. Will likely use 3 straps at a time - corrector plate, eyepiece, x1 finder (Telrad or Rigel). My 4th output will be used to power a heater in my eyepiece case (will have to build an insulated eyepiece case). I have aquired a Humirel RH sensor but was looking at the Sparkfun SHT15 as an alternative as the interfacing is already in place.
Have you given any thought to the PWM code? Such as what conditions to change the PWM timing versus just on and off? I was contemplating trying to have the Arduino set the PWM timing so that each individual heater was on all of the time but just enough to reach the dew point plus a degree or two. this would allow for a more predicatable overall battery drain. the other scenario I was looking at was to intersperse the PWM over the heaters such that only one heater was "on" at any one time. I was trying to figure out which would be most efficient but have not as of yet ran the numbers.
Tom
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