Abstract: Low cost temperature sensor for thermostats utilizing a calibration resistor and a microprocessor with switchable ports wherein said microprocessor selects between high impedance input or an output for a temperature sensing element and a calibration resistor where by selecting the input, the temperature sensing element or the calibration resistor are effectively removed from the circuit thus allowing the low cost temperature sensor to self calibrate itself.

Abstract: A thermostat having a simple battery level detection circuit. The output of an oscillator, having a frequency dependent upon the battery level, is compared to the output of a battery level independent time base. If the two outputs are not in a predetermined relationship, all connected HVAC equipment is shut off.

Abstract: A process of operating an electronic thermostat so that it models the effects of a mechanical thermostat anticipator.

Abstract: The apparatus controlling operation of a digital thermostat mounted in an enclosure corrects the internally measured temperature for heat generated within the thermostat enclosure by the switching element controlling operation of the load, typically a HVAC unit. The actual ambient temperature is derived by subtracting from the internal temperature a correction value which follows the fraction of total time the switching element conducts power for the HVAC unit (duty cycle). The duty cycle is preferably multiplied by a scale factor and the difference between the ambient temperature as currently calculated and the internal temperature to form the correction value.

Abstract: A microprocessor-based power switching circuit responds to a common form of noise by disconnecting power from the controlled apparatus. The microprocessor provides an alternating voltage when power is to be provided, and the alternating voltage is converted by a detector circuit to a voltage close to ground which cuts off a transistor. When the transistor is cut off, an interface circuit places a thyristor which performs the actual power switching, into conduction. Noise on the base of the transistor can only drive it into conduction which then puts the thyristor into non-conduction.

Abstract: A low voltage monitor and microcontroller output monitoring circuit for insuring proper operation of a microcontroller in a furnace control system. A switch connected to a reset port of the microcontroller is capable of putting either a high or low voltage signal at the reset port. A high signal is required for normal operation of the microcontroller. The low voltage monitor connects to a power supply providing power to the microcontroller and causes the switch to provide a low signal to the reset port if the output voltage of the power supply drops below a predetermined level. The output monitoring circuit insures that the microcontroller is operating properly by insuring that the microcontroller is producing an output signal at a predetermined frequency and repetition rate. If the output signal is not at the predetermined frequency, the output monitoring circuit causes a low voltage to be present at the reset port.

Abstract: An analog to digital converter used along with a variable resistive sensing means utilizes the capabilities of a microprocessor to charge and discharge a capacitor. The time required for this capacitor to discharge is dependent upon the value of the variable resistive sensing means. Circuitry is used to create a pulse whose pulse width is equal to the discharged time of a capacitor through the variable resistive sensing means.

Abstract: A gas valve control system including a microprocessor, a first relay, a second relay, flame sensor and a timer. The timer is connected to the switch which is connected in the power supply path of the second relay. The second relay is connected to the valve. Activation of the first relay causes activation of the second relay causing the valve to open. Also, activation of the first relay causes the timer to operate. The flame sensors then must sense flame or else the microprocessor will deactivate the first relay. If the microprocessor fails to deactivate the first relay, the timer causes the switch to open and break the power supply path to the second relay. This in turn causes the valve to close.

Abstract: A heating system controller is suitable for controlling a heating system based on a plurality of sensed control signals representing control parameters. The heating system controller has a first input suitable for being coupled to provide a control signal. The heating system controller also includes a sensor, coupled to the first input, for sensing control signals at the first input, the control signals having a first pattern, a second pattern, or a third pattern detected over at least two successive time periods. The heating system controller includes a control mechanism, coupled to the sensor for controlling the heating system based on the first, second and third patterns. The control mechanism causes the controller to change modes when the third pattern is sensed.

Abstract: A microcontroller and system allowing for more than one trial time in a furnace system, while using only one pin of the microcontroller. An alternating current signal at an input port of the microcontroller causes the microcontroller to allow a first long trial time period. Any direct current signal at the input port causes the microcontroller to allow only a second shorter trial time period. The trial time input port of the microcontroller is placed between two ports which either receive or send direct current signals. Due to this arrangement of the parts and construction of the microcontroller, the microcontroller will fail to the shorter and safer trial time if a fault causes an erroneous signal to appear at the input port.

Abstract: A printed wiring board connector which mechanically supports the board. A connector base has legs which extend away from ends of the base and terminate in stakes which penetrate the board for attachment and electrical connection. Walls extend from the base, arch over the base, and terminate above the base. A conductive protrusion extending from a mounted electrical device is secured between the free ends of the walls and the base providing both support of the printed wiring board and electrical connection.

Abstract: A relay driver circuit which protects a relay against contact degradation. A detector circuit within the relay driver circuit receives an AC signal at a random phase. The detector circuit correspondingly provides a detector signal to a threshold responsive circuit, such as a timer, which drives the relay. The threshold responsive circuit responds substantially the same to a detector signal provided on a positive cycle and to a detector signal provided on a negative cycle. The relay driver circuit is applied to control a blower fan in an air conditioning system.

Abstract: A gas burner control system for controlling operation of a furnace having a blower fluidically connected to the combustion chamber of the furnace utilizes a mass flow sensor for preventing or discontinuing burner operation in the event of a blower failure or a predetermined degree of blockage in the fluid flow path controlled by the blower. The mass flow sensor includes circuit means which enables use of unmatched sensors, enables establishing of a desired value of temperature difference between sensors, enables establishing a temperature difference that is not constant so as to compensate for different ambient air densities, and enables compensating for voltage variations at different ambient air temperatures.

Abstract: A furnace fan control for providing operation of the fan after the termination of the furnace burner in an adaptive manner to provide for longer fan operations after the burner turns OFF, as the burner ON time increases.

Abstract: An ignition control device that utilizes a very sensitive flame rectification signal responsive circuit is disclosed. A printed wiring board arrangement is utilized with a careful arrangement of the conductive areas on the printed wiring board to substantially eliminate leakage paths that can provide a false indication of the presence of flame when none in fact is present.

Abstract: An adaptive control system uses a controller for controlling an air temperature treatment apparatus at a reduced energy consuming level during periods of non-occupancy of a building and for energizing the air treatment apparatus before occupancy so that a desired internal building temperature is reached by a time of occupancy.

Abstract: An electronic control device utilizes a plurality of conductive areas on an associated printed wiring board to create integral dew sensors. The dew sensors are created by providing parallel conductive surfaces that are connected in turn by a resistor to a high impedance switch in the form of the gate of a field effect transistor. In the event that moisture vapor or dew is present in the control device, a conductive path is created that causes the control device to shut down in a safe or alternate mode from the normal mode of operation.

Abstract: A power supply usable with various size loads has an input circuit receiving pulses of voltage at 25 kilohertz. The pulses are modulated in width depending upon the input to a pulse-width modulation IC receiving inputs indicative of the output voltage and current delivered to the load. A backup current limiting circuit comprising a transistor which is biased by the voltage to the load, limits the signal to the pulse-width modulation IC to limit the width of the pulse to maintain the output current within limits.

Abstract: An energy saving thermostat having a selected offset temperature time period previously programmed with means to shift the time period ahead or backward.

Abstract: An energy saving thermostat adapted to be connected to a remote temperature conditioning apparatus for controlling the temperature of air in a space maintains a first temperature during a first time period and a second energy saving temperature during other time periods of the day. The thermostat has a visual indicating means so that when a manually settable switch is pushed, a time interval counter means is energized for indicating and storing a series of pulses each indicative of an hour of setback time into a storage means. The thermostat also has a review button for reviewing the stored time by pulsing the visual indicating means for the number of hours of the time period energy saving temperature.