Abstract: A control used in a two stage HVAC system has a power supply from a 24 VAC transformer which is full wave rectified (D1, D2, D3, D4) to create DC voltages for a microcontroller (U1) and relays (K1-K3). All of the control information needed for the two stage control system is sent to the control from a room thermostat (12) having first and second stage cooling signal terminals (Y1, Y2) over a single line by connecting a diode between the Y1, Y2 terminals creating separate microprocessor recognizable signals.

Abstract: A gas furnace control for two stage gas furnaces which can be used with either a single stage or a two stage room thermostat monitors the length of time the first, low combustion, stage is energized and upon exceeding a selected period of time, e.g., 10 minutes, energizes the second, high combustion stage. Energization of the second stage signal (W2) also energizes the second stage without regard to timing of the first stage.

Abstract: A microprocessor based control for monitoring oil pressure of compressors can use a normally open or a normally closed pressure switch (S1, S2) and LED indicator (LED1) having a diode isolated power supply (VDD−SENSOR) separate from the power supply (VDD) of the microprocessor (U1). Timing of the microprocessor is derived from the frequency of the line (60 Hz). The microprocessor is normally in a sleep mode and is awakened by each 60 Hz interrupt to check the condition of the pressure switch, the accumulated time that inadequate pressure has occurred and whether the relay needs to be energized and then returns to the sleep mode. The resulting reduced power requirement enables extended retention of accumulated “bad” oil time.

Abstract: An integrated heat pump and electrical heat control (12) has thermostat signal inputs (O, W1, W2, G, Y) along with a defrost sensor input (DF_IN). The defrost sensor (22) is located in an outdoor unit (4) which also includes a compressor contactor (CC), condenser fan (16) and reversing valve (18) relays (K4, K3, K2) controlled by micro-controller (U1). The normally closed condenser fan relay (K3) is energized through the defrost sensor forming a hardware lock-out in which the defrost sensor contacts must be closed for relay (K3) to be actuated de-energizing the condenser fan. The compressor contactor (CC) is energized through a low pressure switch (24) and high pressure switch (26) forming another hardware interlock. The evaporator fan is energized by relay (K1) controlled by micro-controller (U1) and matched to the compressor for improved efficiency and comfort.

Abstract: A low cost, microprocessor (U1) based motor controller (10) for driving a half-wave, multiple speed, reversible, DC brushless motor (30) directly from standard AC 50/60 Hz power. A large number of different speed and rotation direction combinations may be chosen before or after the motor is installed using configuration resistors (Rcol1, Rrow1). SIDACs (TS2, TS3) each serially connected to a diode (D6, D5) are connected across respective coils (COIL—1, COIL—2) to clamp the flyback energy in the windings to a few volts when triggered and allow Vemf to float when not triggered. The control adjusts the relative phase timing of commutation during start-up and during running to enhance efficiency. Locked rotor protection is provided by limiting start-up time to a selected period which is followed by a selected cool-off time.

Abstract: An electric control is shown adapted for use with gas furnaces which controls fan motors, ignition controls and a gas valve based on inputs from a room thermostat, limit switches, a flame probe, a flame roll-out probe, and a condensate sensor. A roll-out detection circuit utilizing flame rectification includes a multidirectional roll-out probe 16 coupled to a microcontroller (U2) through an inverter (U3) to provide both fault both protection and fault identification. A condensate sensor (20) in the form of a conductive condensate sensor member is also coupled to the microcontroller (U2) through an inverter (U3) to detect the presence of condensate build-up.

Abstract: A gas fired furnace system (10) has a controller (14) controlling the supply of gas through a gas valve (12) and air for combustion by means of an induced air draft fan (28), ignition of the gas by means of ignitor (22), the delivery of heated air from a heat exchanger (20) by means of an air blower (34) in response to signals from a thermostat (42). A selected constant flow of air for combustion is provided by controlling the speed of the motor driving the induced motor fan (28) despite changes which may occur in back pressure. Induced draft fan motor parameters proportional to motor torque and motor speed are read on an ongoing basis and inputted to controller (14) which computes a desired voltage and compares that with referenced data stored in the controller memory and makes corrections to the speed of the induced draft fan motor to maintain the constant air flow.

Abstract: A gas fired furnace system (10) has a controller (14) controlling the supply of gas through a gas valve (12) and air for combustion by means of an induced air draft fan (28), ignition of the gas by means of ignitor (22), the delivery of heated air from a heat exchanger (20) by means of an air blower (34) in response to signals from a thermostat (42). A selected constant flow of air for combustion is provided by controlling the speed of the motor driving the induced motor fan (28) despite changes which may occur in back pressure. Induced draft fan motor parameters proportional to motor torque and motor speed are read on an ongoing basis and inputted to controller (14) which computes a desired voltage and compares that with referenced data stored in the controller memory and makes corrections to the speed of the induced draft fan motor to maintain the constant air flow.

Abstract: An electric control for gas furnaces which controls a two speed main blower fan and an induction draft fan based on inputs from a room thermostat, a high limit and an ignition control including a gas valve. The control has a circuit board having a power supply for providing 24 volts DC current source to drive DC relays and a 5 volt DC power source to power a microprocessor. 24 volt AC input signals are coupled to the input ports of the microprocessor through current limiting resistors and to AC ground through pull down resistors. AC ground is also connected to the IRQ port of the microprocessor. The output ports of the microprocessor are connected to a relay driver which in turn is connected to the relays. Several breakaway tabs in the board provide optional features such as eliminating a normally provided draft delay timing function. Test pads are provided on the board so that the board can be tested during manufacture.

Abstract: An electronic control for gas furnaces controls a two speed main blower fan and an induction draft fan based on 24 volt input signals from a room thermostat, a high limit and an ignition control including a gas valve. The input signals are coupled to input ports of a microprocessor through current limiting resistors and to AC ground through pull down resistors. AC ground is also connected to the IRQ port of the microprocessor. Output ports of the microprocessor are connected to a relay driver which in turn is connected to relays for energizing and de-energizing the fans. The control calibrates itself on a continuing periodic basis to read the AC inputs synchronously at the peak of their wave and can switch the relays asynchronously based on the Real Time Clock of the microprocessor or can be switched synchronously by providing a selected delay so that contact engagement and disengagement occurs at or near the zero crossing of the AC line voltage wave form.

Abstract: A gas fired furnace system (10) has a controller (14) controlling the supply of gas through a gas valve (12) and air for combustion by means of an induced air draft fan (28), ignition of the gas by means of ignitor (22), the delivery of heated air from a heat exchanger (20) by means of an air blower (34) in response to signals from a thermostat (42). A selected constant flow of air for combustion is provided by controlling the speed of the motor driving the induced motor fan (28) despite changes which may occur in back pressure. Induced draft fan motor parameters proportional to motor torque and motor speed are read on an ongoing basis and inputted to controller (14) which computes a desired voltage and compares that with referenced data stored in the controller memory and makes corrections to the speed of the induced draft fan motor to maintain the constant air flow.

Abstract: An electric control is shown for gas furnaces which controls fan motors and ignition controls based on inputs from a room thermostat (32), a high limit control and an ignition control (14) including a gas valve. A flame sense circuit (42, 42') is coupled to a microprocessor (U2) and includes a flameprobe (P1) energized by line power through a capacitor (C3) via a quick connect (QC31). A capacitor (C4) is charged by a 5 volt DC source through resistor (R12) and inputted to an inverter (U3, S2) which provides a low signal to the microprocessor when no flame is present. When a flame is present the capacitor (C4) discharges through the flame causing the inverter to change state providing a high to the microprocessor indicating that a flame is present. A diagnostic network comprising a low leakage diode (CR10) and serially connected resistor (R11) is coupled between the microprocessor (pin 8) and the input of the inverter (U3) so that the operation of the flame sense circuit can be tested.

Abstract: A low voltage terminal board interfaces a fan motor with a field thermostat. The board includes a power supply providing a 24 volt DC power source for driving an electronic air cleaner relay and fan motor control lines and a 5 volt DC power source for providing optical isolation and timing logic. Several heater stage signals are connected to a diode interlock network so that no matter which signal is generated the first electric stage heater is energized. A first optically coupled isolator receives a 240 volt AC input whenever the first stage electric heater is energized with the isolator output controlling energization of a heat or medium speed operation of the fan motor. Second and third optically coupled isolators receive a 24 volt AC input indicative of continuous fan operation and compressor operation respectively with the outputs controlling energization of low (on/off) fan speed operation and high speed fan operation respectively.

Abstract: A low-cost, highly-responsive temperature sensor has a thermistor element surface-mounted in a circuit defined by an electrically-conducting layer of a three-layer circuit substrate to be in close thermal coupling to a metal base layer on an opposite side of the substrate. The base layer is adapted to be disposed in heat-collecting relation to a surface whose temperature is to be monitored. An intermediate layer of the substrate has a binder electrically insulating the thermistor from the metal base layer and has thermally-conducting particles dispersed in the binder to improve thermal coupling of the thermistor to the heat-collecting substrate base layer. The circuit defines terminal pads surface-mounting the thermistor element at one end of the substrate and defines interconnected terminal pads at an opposite end of the substrate which are connected to device lead wires in substantial thermal isolation from the thermistor element.

Abstract: An electric control for gas furnaces which controls a two speed main blower fan and an induction draft fan based on inputs from a room thermostat, a high limit and an ignition control including a gas valve. The control has a circuit board having a power supply for providing 24 volts DC current source to drive DC relays and a 5 volt DC power source to power a microprocessor. 24 volt AC input signals are coupled to the input ports of the microprocessor through current limiting resistors and to AC ground through pull down resistors. AC ground is also connected to the IRQ port of the microprocessor. The output ports of the microprocessor are connected to a relay driver which in turn is connected to the relays. Several breakaway tabs in the board provide optional features such as eliminating a normally provided draft delay timing function. Test pads are provided on the board so that the board can be tested during manufacture.

Abstract: A fan control board having a central low voltage wiring center as well as a safety interlock for electric heaters. The interlock uses diodes to insure proper fan operation in the event of miswiring of the heater sequencers. Another feature is a quick connect for the time delay relay which permits easy insertion and removal thereof for replacement and/or cleaning. Diode circuits are provided in both the circuit to normally power the fan motor as well as in the circuit to power the PTC resistor which closes the fan motor circuit with the circuit which powers the PTC resistor also being connected across the fan motor circuit to provided rectified power to the fan circuit and permit the fan motor to turn on concurrently with the application of power to the PTC resistor to prevent the heater from being turned on prior to the fan.

Abstract: A fan control board and circuit having a central low voltage wiring center as well as a safety interlock for electric heater in which the interlock uses diodes to ensure proper fan operation in the event of miswiring of the heater sequencers. Another feature of the invention is a quick connect for a time delay of the circuit which permits easy insertion and removal thereof for replacement and/or cleaning.

Abstract: The disclosure relates to a system for measuring relative humidity and temperature wherein there are provided three controlled switching matrices, a first of the matrices determining whether a current for determining temperature or relative humidity is to be fed via a diode to a system voltage output from when the voltage output will be converted to an appropriate temperature or relative humidity reading. The remaining two matrices are each controlled by an oscillating voltage which alternates the output or input terminal thereof depending upon whether the oscillating voltage is positive or negative. This causes current to be passed through a humidity responsive resistor in opposite directions during each half cycle of the oscillating voltage. In the case of humidity sensing, the diode used for measuring temperature also acts as a temperature compensating device for the humidity sensor, thereby having a dual function in the system.

Abstract: Differentially connected capacitive sensors are mechanically coupled with the flexible capacitor plate of one sensor coupled to the source of pressure to be measured, the flexible capacitor plate of the other sensor coupled to ambient pressure. In a second embodiment, inaccuracies due to forces on the flexible plate are minimized by providing a housing with a tapered inner wall, an O-ring and a support to apply a radial load to the sensor due to clamping action from the tapered housing against the O-ring to provide a seal for the pressure sensing chamber. In a further embodiment, the cost of fabrication of the pressure transducer is minimized by providing the housing as a one piece cup. The electronics are mounted on the exterior surface of the low pressure side of the ceramic capacitor pressure sensing element and sealed in thereat by potting with an epoxy.