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HikerBob,
Looked into the Duemilanove. Wow! Have not dealt with uC for a while (evident from my AT90S8515 reference). Subsequently have ordered a Starter Kit and am downloading and trying to absorb the wide range of information available. Looks like this will make implementation simple on the hardware side.
All of my experience has been programming devices in Assembly language. I am looking forward to being able to use a higher level language. Am still looking into the LOG function call - not documented in the Atmel data sheet at first glance - which does not mean it is not a higher level translation of lower level commands. Do I remember my math on this - no!
Now for Dew Point calculations - I too was using the Wikipedia formulas as they are standard. On the praries of Canada, and especially during the winter months, it is unusual for the RH to get over 50%. However, with the memory of the Duemilanove (ATmega328), I can implement using the Simple approximation for RH above 50% and Closer approximation below 50%. I have discovered that there are no published approximations for frost point. This will likely have to be a table.
My eventual hardware implementation - final version - will likely be a custom PCB / Controller with bare minimum components supporting:
1) 4 channel control (with manual on/off selection).
2) Automatic dew/frost point temperature determination.
3) Optic temperature measurement.
4) Option for manual control by varying the PWM for each channel.
5) Channel on/off and heating on LED indicators.
6) Undecided on a possible 7 segment LED information readout (LCDs freeze here - not a good thing).
It will use the ATMEL ATmega328 with Duemilanove bootloader at the core. I sould probably review my sensor selections as well.
Thanks to you and Peter for setting me on a much simpler journey to the end goal. I find it so much better to develop and understand the details in something rather than to purchase a item that may not do exactly what I want it to do. As battery conservation during freezing temperature observing is a priority for me - no commercial product actually meets my needs.
Tom
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