I have do it a couple a years ago with only one 723 in to99 package which
is the heater and the controller of the crystal temperature, but it's
working only for small crystals and with a good stability near 50...60 C.
Note that's for a wrong cut of the crystal the stability is worse at
60C than without thermal compensation at 25 C

Vasile

On Wed, 3 Oct 2001, Mike Hardwick wrote:

> 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...
>
> Mike Hardwick, for Decade Engineering -- <http://www.decadenet.com>
> Manufacturer of the famous BOB-II Serial Video Text Display Module!
>
> --
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>

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