> Thermal control hardware can be simplified if you have a micro in the
> system... Use a DS18S20 or similar temp sensor (takes one I/O pin) and a
> software-controlled heater (one more I/O pin). The heater can be a cheap
> power transistor in a constant-current circuit (with another small
> transistor). With some attention in software to thermal delay, etc., you
> can get excellent results with this approach. A PWM generator can
> "linearize" heater response...

If you are just trying to hold a preset temperature, then you don't need a
linear temperature sensor.  It only needs to be monotonic.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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