A user-friendly, network-connected learning
thermostat is described. The
thermostat is made up of (1) a wall-mountable backplate that includes a low-power consuming
microcontroller used for activities such as
polling sensors and switching on and off the
HVAC functions, and (2) separable head unit that includes a higher-power consuming
microprocessor, color LCD backlit display,
user input devices, and
wireless communications modules. The
thermostat also includes a rechargeable battery and power-stealing circuitry adapted to harvest power from
HVAC triggering circuits. By maintaining the
microprocessor in a “sleep” state often compared to the lower-power
microcontroller, high-power consuming activities, such as learning computations,
wireless network communications and
interfacing with a user, can be temporarily performed by the
microprocessor even though the activities use energy at a greater rate than is available from the power stealing circuitry.