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I've got moving again on an Ardunio controlled PWM heater. I had the whole thing on hold for a while dithering over heater straps, I did some work on making my own and decided that I was going to spend a fair bit anyway and was no confident that I'd get a good result. I ended up getting a number of Dew-Not heater straps which so far seem great.
The controller is more complex than many find necessary but component count is low (and the ugly bit's are in the power stage which I'd need anyway) and I'm using it as a learning exercise to get across some of the technologies.
I've got the important parts of the dew heater controller working
- 4 independent PWM channels each with a dedicated temperature sensor.
- Dew point calculation based on ambient temp and relative humidity (I expect that the calculations will be suitable for the conditions I observe in)
I'm planning some extra work soon. A red on black serial LCD screen, a current shunt/sensor and an extra Ardunio are on order. I'm planning to
- Add voltage monitoring (2 resistors, some code and a hookup to an analog pin on the ardunio) to try and avoid running batteries right down.
- Add current monitoring, combined with the voltage monitoring and controlled cycling of the power channels and the controller should be able to work out what's hooked up to it and adjust the behaviour of the different channels to suit. I'm guessing that a 1.25" eyepiece will benefit from different heating patterns vs a large corrector plate or the front lens of a finder scope.
- Add the LCD so that I can see on the controller what's happening, I can monitor via a laptop currently but that's not always ideal or practical
- Tidy up some wiring
- Swap the ardunio over to a cheaper and slightly more basic model (and use the current one for developing something else)
- Fix some indicator led's which are not working
- Review the code to see if there are tidy up's I can do
Bob
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