Honeywell G.m.b.h.

Victor H Rigotti

James T Russo

Michael R Levine

Nicholas Skogler

Anthony C Cairo

Matthew B Levine

Roger Clark

The present invention is a technique for a defrosting operation of a heat pump. External air provides the heat for defrosting the exterior heat exchanger by operating the exterior fan during times when the compressor is not operating, the temperature of the exterior heat exchanger is below freezing and the exterior air temperature is above freezing. In accordance with one embodiment of the present invention the temperature of the exterior heat exchanger and the exterior are measured via separate temperature sensors. In accordance with an alternative embodiment, the exterior heat exchanger temperature is measured via a single temperature sensor and the exterior fan is operated for a predetermined interval of time after the compressor is stopped. Thereafter the exterior fan is operated only so long as the temperature remains at freezing. In a still further embodiment, the exterior fan is operated only so long as it remains less than or equal to freezing and does not reach a plateau at less than freezing. The operation of the exterior fan after deactuation of the compressor may be inhibited throughout an interval of time, if the plateau temperature was less than freezing.

Heat pump defrosting operation

The present invention is a technique for a defrosting opereation of a heat pump. External air provides the heat for defrosting the exterior heat exchanger by operating the exterior fan during times when the compressor is not operating, the temperature of the exterior heat exchanger is below freezing and the exterior air temperature is above freezing. In accordance with one embodiment of the present invention the temperature of the exterior heat exchanger and the exterior are measured via separate temperature sensors. In accordance with an alternative embodiment, the exterior heat exchanger temperature is measured via a single temperature sensor and the exterior fan is operated for a predetermined interval of time after the compressor is stopped. Thereafter the exterior fan is operated only so long as the temperature remains at freezing. In a still further embodiment, the exterior fan is operated only so long as it remains less than or equal to freezing and does not reach a plateau at less than freezing. The operation of the exterior fan after deactuation of the compressor may be inhibited throughout an interval of time, if the plateau temperature was less than freezing.

The present invention is an adaptive method and apparatus for detecting the formation of frost in a heat pump. The compressor cycle is interrupted and a defrosting operation is begun if the difference between the exterior ambient temperature and exterior heat exchanger temperature exceeds a difference function of the exterior ambient temperature. The length this defrosting cycle is measured and the difference function is altered if the measured length deviates from a predetermined length of time. The frost formation difference function is initially set as a linear approximation. Thereafter the difference function value at the particular exterior ambient temperature is increased if the length the defrosting is greater than an upper limit value of six minutes and decreased if the length the defrosting is less than a lower limit value of four minutes. In the preferred embodiment, the exterior heat exchanger temperature is measured by a sensor and the exterior ambient temperature is determined once each compressor cycle from this measured temperature.

Heat pump with adaptive frost determination function

The present invention is a method and apparatus for determining the exterior ambient temperature in a heat pump. In accordance with the prior art the heat pump defrosts the exterior heat exchanger if the exterior heat exchanger temperature has a predetermined relationship to the exterior ambient temperature. The exterior heat exchanger temperature is measured directly via a temperature sensor. The improvement of the present invention includes operating the exterior fan after operation of the compressor, while repetitively measuring the temperature of the exterior heat exchanger until reaching a plateau temperature other than freezing. The exterior ambient temperature is set to the plateau temperature. In the event that the plateau temperature equals freezing, the exterior ambient temperature is set equal to a compromise temperature slightly above freezing, preferably 34 degrees Fahrenheit.

Heat pump with single exterior temperature sensor

The present invention is a technique for forming a signal representing the operator adjustment of a potentiometer. This technique consists of measuring the reference time constant of the resistance between the fixed terminals of the potentiometer and a capacitor, measuring the variable time constant of the resistance of potentiometer between a fixed terminal and the terminal variable by an operator setting and this same capacitor, and again measuring the reference time constant of the resistance between the fixed terminals of the potentiometer and the capacitor. These time constant measurements are made by discharging the capacitor, charging the capacitor through the appropriate terminal of the potentiometer and measuring the time required for the voltage across the capacitor to reach a predetermined threshold level. This measurement sequence is repeated if the two measures of the reference time constant differ by more than a predetermined amount. The digital ratio of the variable time constant and the reference time constant is then calculated. This digital ratio is the representation of the operator adjustment of said potentiometer.

Potentiometer setting detection by measuring the ratio of RC time

The present invention is a technique for forming a digital signal representing an environmental condition. The technique consists of measuring the variable time constant of an analog sensing device having a variable resistance dependent upon the environmental condition and a capacitor as well as measuring the reference time constant of a precision fixed resistor and the same capacitor. The time constants are measured by discharging the capacitor, charging the capacitor through the appropriate element and measuring the time for the voltage across the capacitor to reach a predetermined level. Lastly, the digital ratio between the two time constants is formed. This digital ratio is the digital representation of the environmental condition sensed by said analog sensing device.

Analog to digital conversion by measuring the ratio of RC time constants

The present invention is a technique for operator entry of a time program into a programmable device. An operator adjustable input device having associated time indicia is employed to enter a time signal indicative of a time a selected time. A manual control state input device enables selection of one a control state. When the programmable device is in a program mode the selected control state is stored in a program memory at a location corresponding to the selected time. This program memory stores a program of control states for particular times. When in a control mode a clock signal indicative of the current time permits recall of the control state for the current time, thus permitting control in accordance with the recalled control state. In accordance with the preferred embodiment the programmable device is an electronic thermostat. The operator adjustable input device enables input of the times for storage of temperature offsets in the program mode and enables input of a set point temperature in the control mode. The thermostat control function seeks to maintain the temperature at the sum of the set point temperature and the temperature offset for the current time.

System for time programming of states by communicating time data via a

The present invention is a method for specifying a constant in a digital electronic system. This technique employs the ratio of resistances between a reference resistor and a constant specifying resistor. The time constant of the constant specifying resistor and a capacitor is measured by discharging the capacitor, charging the capacitor through the constant specifying resistor and counting the number of predetermined time intervals required for the voltage across the capacitor to reach a predetermined threshold voltage. A similar time constant measurement is made for the reference resistor and the capacitor. The same conditions are employed as far as possible during these two measurements to insure the only differences are in the value of the resistances. The externally specified constant is computed from the digital ratio of the time constant of the constant specifying resistor and the time constant of the reference resistor. This technique is particularly adapted for use in a microprocessor system having several tristate output lines.

External constant specification in a digital electronic system

A control device for energization of a load employs a bidirection triggerable solid state switching device connected in series with an alternating current power source and the load. In order to prevent the passage of excessive, potentially destructive currents through the switch if the load is shorted out, the microprocessor which controls the energization of the switch senses the time required for the voltage across the switch to attain a predetermined value. If the load is shorted the potential difference across the switch increases and attains the predetermined value a shorter time after zero-crossing of the alternating current. When this occurs more than a predetermined number of consecutive times, the generation of triggering pulses for the solid state switch is inhibited for a predetermined time. In the preferred embodiment the control device is a thermostat for controlling a temperature modifying load such as a furnace or air conditioner.

Overload protection circuit for solid state switch

An electronic thermostat includes selectable multiple predetermined temperature programs of desired temperatures over a repetitive time cycle. A manually operable temperature program selector enables recall of a desired temperature for a particular time from a temperature program memory in accordance with the selected predetermined temperature program. This desired temperature is compared to the ambient temperature in order to generate control signals for a temperature modifying device. In the preferred embodiment, the multiple temperature programs each consist of digital signals indicative of either a normal temperature or a set-back temperature. A separate operator actuable set point device determines the normal temperature. When the normal temperature is indicated, the thermostat controls the temperature modifying load to restore the selected normal temperature. When the set-back temperature is indicated, the thermostat controls the temperature modifying load to restore a temperature which is a predetermined number of degrees offset from the selected normal temperature. The set-back temperature is lower in a heating mode and higher in a cooling mode enabling reduced energy consumption in the temperature modifying device. In the preferred embodiment, the number of degrees of the offset is selectable via an operator control.

Electronic programmable thermostat

The present invention is an electronic thermostat having correction for the self heating due to the semiconductor switching device used to switch a temperature modifying apparatus on. This invention includes a semiconductor power switching device disposed on an upper portion of a vertically oriented circuit board, a first thermistor disposed on the circuit board at a lower portion thereof remote from the semiconductor power switching device, and a second thermistor disposed on the circuit board at a portion intermediate between the semiconductor power switching device and the first thermistor. A corrected ambient temperature is generated from the temperature indicated by the first thermistor and the difference in indicated temperature between the second thermistor and the first thermistor. The state of the semiconductor power switching device is then controlled based upon the relationship between the corrected temperature and a desired temperature.

Digital electronic thermostat with correction for triac self heating

The present invention is a control range display for an electronic thermostat. A plurality of individually actuable display segments are disposed in a line. Each of these display segments represents a particular temperature. The control range of the electronic thermostat is displayed by actuating the display segments representing the upper and lower preselected temperatures and all display segments therebetween. In the preferred embodiment each of these display segments is a liquid crystal display device. The preferred embodiment enables indication of the present temperature by actuation of a single display segment representing that temperature upon selection of a normal mode and an indication of the control temperature range by actuating display segments in the manner noted above upon selection of a program mode. The preferred embodiment further includes a removable mask containing a temperature scale indicia marked in a preselected geared measurement which can be disposed beside the line of display segments of the display means, thereby indicating the particular temperature represented by each display segment in the preselected unit of measurement.

Temperature range display device for electronic thermostat

The present invention is an apparatus and method for bidirectional alteration of a multivalue parameter from an initial value using a two-state manual input. In accordance with the present invention, the multivalue parameter is altered from its initial value in a first direction if the manual input is in a preselected state for less than a predetermined period of time. If the manual input is in the preselected state for a period of time longer than this first interval of time, then the multivalue parameter is altered from its initial value in the opposite direction. Additionally, if the manual input remains in the preselected state for additional periods of time, the value of the multivalue parameter is further altered in the opposite direction for each such additional interval. This invention is taught as useful in providing programs for programmable memory devices, in particular programmable thermostats.

Manual switch for altering a parameter in opposite directions based on

An electronic programmable thermostat for the control of a furnace or air conditioner is useful as a replacement for a conventional non-programmable thermostat and mounts on the non-programmable thermostat's wall plate to achieve support, electrical connection with the load and power supply, and the use of certain manual controls supported on the wall plate. The programmable thermostat employs a circular printed circuit board supporting its electronic components, which include a potentiometer for operator adjustment of desired temperature. A flat circular knob supported on the potentiometer shaft and an annular bezel cover the thermostat and allow access to the manual controls supported on the wall plate. The potentiometer and a temperature sensing thermistor control the frequency of a pulse generator which provides input to a counter. The resulting digital signal is compared with a digital signal generated under control of a clock and manually actuable programming switches, to generate an output control signal for the load.

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Ann Arbor, MI, United States of America

Victor H Rigotti