I worked on a project once where a part was temperature sensitive. Another engineer, not me stuck a Peltier device on the part along with a temperature sensor and a crude servo using an op amp. This was not complex, a simple design and it held to about 1/2 degree C. Basically made an oversized part with JB Weld epoxy and $15 in parts. Something like that wold have put your clock spot-on.
Yes you can design very sophisticated controls and insolation and get marginally better results at 100x cost. Did that one too. Used water cooling and a vacuum chamber for insulation. That was more of a plumbing job than an electrical job, getting the signals and water lines and vacuum lines not to leak. I learned to be a fan of designs that to 90% of perfect with 10% of the cost. On my Rb oscillator I took the cheap/easy route this time. There is a temperature sensor on the heat sink and a fan has its speed controlled to keep the heatsink at constant temperature. Used just one chip to build the fan controller an 8-pin AVR running an Arduino sketch. The Rb is now pretty stable Those cheap 32K crystals might be really good if you find a low cost why to temperature control them. Strapping it so some one's wrist seems the best and lowest cost way, just don't remove it. On Tue, Apr 11, 2017 at 12:21 AM, Morris Odell <vilgo...@bigpond.net.au> wrote: > > > Most wristwatches do not have any temperature compensation. If worn, the > wristwatch is pretty close at the 25°C (the human body is a quite good and > temperature stable oven). The difference only starts to > show when the > watch isn't worn for long periods of time. > > That explains my experience with the first microcontroller based clock I > built years ago. I used a commercial module with a micro and some > accessories including a watch crystal for timing. It's on a window ledge > facing west in Australia where the temp varies during the year by 40°C. It > was always a bit fast and I spent a lot of time checking my code to make > sure I was dividing it by the right amount. I eventually tamed it by > programming a short pause at 3:00 am. I'm sure the temp of the watch > crystal is very rarely 25°C!! > > Morris > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/ > mailman/listinfo/time-nuts > and follow the instructions there. > -- Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.