Summary of the digital thermostat
According to broad aspects of the invention, an energy conserving thermostat control system utilizes digital control circuits for regulating the operation of heating and/or air conditioning systems for maintaining the ambient temperature of a controlled area at a selected night temperature and at a selected day temperature during predetermined times of night and day, respectively. The digital thermostat includes a digital data display for simultaneously displaying present time and ambient temperature. Slide switches are provided for setting and indicating set point information such as day temperature, night temperature, night-to-day transition time, and day-to-night transition time. The switch contacts of the slide switch are multiplexed to the digital data display driver conductors for conveying time and temperature set point data during alternate time and temperature scan intervals.
The digital thermostat control unit is adapted for use with a heating or cooling system which includes a source of operating power characterized by an alternating current waveform and a system control relay connected in series of electrical relation therewith without interfering with the operation of the heating or cooling system. Operating power for energizing the fan coil unit control is provided by a power divider circuit for energizing or de-energizing the system control relay in response to the presence and absence of a command signal from the room thermostat control unit, respectively, and for providing a continuous source of operating power for the belimo control unit without interfering with the operating state of the system control relay.
According to an important feature of the invention, control means are coupled to the digital data display for periodically applying present time and ambient temperature data signals to the digital data display during a display interval and for interrupting the data signals during scan intervals preceding and following the display interval. The driver conductors are strobed to determine time set point information during the preceding scan interval and are strobed again to determine temperature set point information during the following scan interval. Data return conductors are coupled to each of the set point switches for conducting a return pulse when the driver conductor to which it is connected receives a strobe pulse.
The foregoing and other objects, advantages and features of the invention will hereinafter appear, and for purposes of illustration, but not of limitation, an exemplary embodiment of the subject invention is shown in the appended drawing.