Abstract: An apparatus for and method for protecting the electronic circuitry within a gas appliance. The electronic circuitry is arranged on a circuit board. A temperature sensor, located on the circuit board is periodically read to determine the current temperature. If the current temperature exceeds a first predetermined value, a microprocessor commands a stepper motor to reduce the input fuel pressure to the main burner. If the current temperature is within an acceptable range, the microprocessor permits the user to increase main valve outlet pressure.

Abstract: A burner system for use in applications such as a gas fireplace insert has a main burner, a standing pilot burner, a burner control unit, and a fuel valve. In one embodiment, the fuel valve and burner control unit receive power from a power source such as a thermopile mounted to receive energy from the pilot burner. The burner control unit includes a switch controlling power to the fuel valve and a RF receiver. The RF receiver controls the opening and closing of the switch responsive to encoded RF signals transmitted to it by a remote transmitter.

Abstract: A humidity sensing circuit uses a humidity sensitive capacitor as a circuit element in an RC control network for a timer/multivibrator circuit. As the voltage on one plate of the capacitor swings between charge and discharge voltage limits and corresponding triggering voltage values for the timer/multivibrator, the other plate of the capacitor is held at a voltage substantially midway between the charge/discharge voltage limits to thereby cancel out any time averaged net DC component on the capacitor, to reduce stress thereon and extend its life. A power-down feature is disclosed for removing all voltage across the capacitor between sensing intervals.

Abstract: A resistance to frequency circuit for measuring the ambient temperature on a thermostat. The temperature measuring circuit comprises a first Schmitt trigger NAND gate, a rectifier, a capacitor of which one terminal is electrically connected to ground, a first resistor, a thermistor and possibly a second resistor. The capacitor is connected with the cathode electrically connected to ground, the anode is electrically connected to the first input of a NAND gate. The output of the NAND gate is electrically connected to the anode of the rectifier. The cathode of the rectifier is electrically connected to both the thermistor and the first resistor. The second terminal of the first resistor is electrically connected to the anode of the capacitor and the first input to the NAND gate. The thermistor is electrically connected to a tri-state buffer of the microprocessor. The circuit uses the open drain output ports of a microprocessor to provide the multiplexer function of the A/D.

Abstract: A process which is periodically executed by a programmable thermostat of a heating and cooling system which controls the temperature of a defined space within a structure subjected to a variable external environment. The process advances by an increment of time, .DELTA.t, when the set point temperature of the thermostat changes from an occupied set point temperature to an unoccupied set point temperature. The magnitude of .DELTA.t is a function of the thermal lag of the structure, its external environment, and an amount of temperature change that is acceptable to occupants of the space. Each time the process is executed, the magnitude within predetermined limits of .DELTA.t to be used the next time the process is executed is recalculated.

Abstract: A setback thermostat controlling a device which holds and changes the temperature in a space includes the capability of sensing and recording the difference between the time at which recovery to a new setpoint temperature occurs and the selected time at which this temperature is specified to be reached, and if the difference is nonzero, calculates a new time at which to begin recovery the next time a change to the new temperature is specified. The calculation of the time at which recovery begins takes account of the fact that greater time is required to achieve a one degree temperature change near the new setpoint temperature than far from it because of the additional thermal load on the space as temperature nears the new set point. A non-linear function is used to calculate the time at which recovery to the new temperature is begun. The invention is included in a method for operation of the device which changes the space's temperature.

Abstract: A thermostat is disclosed which includes a Proportional-Integral-Derivative (PID) controller and a means for disabling the PID controller for selected periods. The PID controller is disabled during a temperature recovery period, which can be triggered by the occurrence of one or more of many preselected events. The PID controller is re-enabled when the thermostat setpoint less a void offset temperature is reached. To reduce error in future temperature recovery periods, the void offset temperature is adjusted after a temperature recovery by adding the amount of error to the void offset temperature to create a new void offset temperature for use in a next temperature recovery period.