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Glen. I should stick with what you have if you are happy. Absolutely no reason to adopt this at all, that I can think of.
It's just a DIY temperature controller. At this stage a single channel. Mirroring the existing circuit minus the power section and swapping inputs to the non-inverting and inverting pins, as required, it will eventually have 4 channels off 1 chip. Cooling, dew heaters etc, coffee warmer, glove and boot heaters if you want.
Temperature control is much better than previously indicated. The sensor was originally strapped directly to the back of the TEC. Since, I have added a piece of left over 1.2 mm copper to the test rig to emulate a CF - it maintains +/- 1 - 2mV (10 - 1/5th degree) easily. The fluctuations are helpful in that the dithering effect is averaged out by the thermal mass - the integral part of the plant, to use Steffen's words (correct me if I am wrong).
I have some mini voltmeters on order and these will be added to the schematic as a temperature reference. As mentioned in the first post, the TMP36 is a linear device and mV is easily converted to temperature.
500mV = 0C; 400mV = -10C and linearly between. Just need a voltmeter, which is a pain and only temporary - no idea when the voltmeters will arrive by ordinary mail from China?
Note: I have decided not to add temperature reference compensation as mentioned previously. Given the range of systems likely (if it ever gets used) the operator can easily set the temperature using the potentiometer and allow for individual system variation. Once set it is as far as I can tell based on testing, very accurate for astronomical purposes.
I recommend running it between 6 and 12 volts.
I will work on a 4 channel board if anyone is interested, otherwise the finished circuit is below in 4 separate sheets. Power section, temp sensor input, OPAMP section and then the TEC high current side. Sheets 3 and 4 tie it all together - note the AGND and DGND separation.
If anyone wants the kicad .sch file - you are probably using Linux - I will post it as well.
It's educational and a lot of fun.
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