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Digital Thermostat Schematic Wanted

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Anybody have a schematic they care to share for a digital thermometer/thermostat that has a low and high setpoint. A adjustable hystersis would be a bonus as well. The only thing I have been able to find on the internet incorporates a LCD module from Radio Shack.


New Member
I have a partially completed thermostat diagram. It uses a LM34 to measure inside temperature
which is read on a digital panel meter. The reading is hooked up to a dual comparator. Then I
set a "High" and "Low" voltage and feed each to a separate section on the dual comparator. When-
ever the temperature is either below or below the settings, the thermostat turns ON or Off, depend-
on whether it is air conditioning or heating. Because the settings are variable, the SPAN is set by
the settings. I am 80 years of age and have been delayed from completing the printed circuit board
by everything, except age. Pepos S. Dounson, 914 W. Mistletoe Avenue, San Antonio, TX 78201-5649. Area 210 733-1377. [email protected]


Well-Known Member
Hi Bryan,
The TC620/621 from Microchip sounds like the chip you need. I've attached the datasheet below for you to read.

Regards Bryan1

View attachment TC620.pdf
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