Abstract: A two-terminal electronic thermostat connectable in series with an electrical heater and a source of AC power and selectively providing AC power to the electrical heater, and a power supply incorporated in the thermostat for providing DC power to the control circuitry of the thermostat, includes a relay connectable in series with the electrical heater, a control circuit for selectively actuating the relay, an ambient temperature sensor and a potentiometer for setting a set point temperature. The power supply includes a current transformer having its primary winding connected in series with the relay and the electrical heater. The power supply also includes a first bridge rectifier circuit, a second bridge rectifier circuit connected to the secondary winding of the current transformer and a capacitor divider network formed from first and second capacitors and providing a desired DC voltage to the control circuit. The first capacitor is coupled to the first bridge rectifier circuit.

Abstract: A humidity control device includes a microcontroller, a variable impedance humidity sensing circuit and a zero crossing detector circuit. The humidity sensing circuit and zero crossing circuit are provided with an AC line voltage and both have outputs which are provided to the microcontroller. The humidity control device also includes a semiconductor switch circuit which switches the AC line voltage to an external electrical device, such as a dehumidifier or heater, at the zero crossing.

Abstract: An automatic thermostat which automatically reprograms itself after a power outage without the need of a backup battery or other storage device includes a temperature sensor, a set temperature potentiometer, a setback temperature potentiometer and an ambient light sensor. The thermostat also includes a microprocessor which is responsive to signals from the temperature sensor, the set and setback temperature potentiometers and the ambient light sensor. The microprocessor controls a display which displays the set temperature, the setback temperature and the actual temperature. A power outage detector detects when there is a power outage and triggers the microprocessor to reprogram itself by rereading the signals from set temperature potentiometer and the setback temperature potentiometer. A relay is controlled by the microprocessor to selectively provide power to a heating or air conditioning unit.

Abstract: Heating pads using positive temperature coefficient (PTC) resistance material are subject to fire risk if one of the conductor wires between which the PTC material extends should break and produce an electric arc. Protection by fuse and a fuse-blowing circuit responsive to fire detection must allow for an immense inrush of current when the cold pad is turned on. A heat setting control using a microprocessor can reduce the fuse rating by chopping the a.c. heating current for a short start-up period following with full-on feed until the heat setting is reached. The presence of a microprocessor allows response to a safety circuit that detects a break in a heater feed or return conductor before much excess heat develops, so that the microprocessor can turn off the heater switch. That response is so quick that it can be confirmed by repeated detection after very short pauses before the heater switch (a triac) is turned off.

Abstract: Heating pads using positive temperature coefficient (PTC) resistance material are subject to fire risk if one of the conductor wires between which the PTC material extends should break and produce an electric arc. Protection by fuse and a fuse-blowing circuit responsive to fire detection must allow for an immense inrush of current when the cold pad is turned on. A heat setting control using a microprocessor can reduce the fuse rating by chopping the a.c. heating current for a short start-up period following with full-on feed until the heat setting is reached. The presence of a microprocessor allows response to a safety circuit that detects a break in a heater feed or return conductor before much excess heat develops, so that the microprocessor can turn off the heater switch. That response is so quick that it can be confirmed by repeated detection after very short pauses before the heater switch (a triac) is turned off.

Abstract: A dual compartment single evaporator refrigerator and temperature control apparatus that effectively controls two compartment temperatures by making the evaporator fan control independent of the compressor cycle. The compressor cycle is initiated by the fresh food compartment temperature, runs for a predetermined minimum time, and is terminated by the freezer temperature. The evaporator fan runs with the compressor and is terminated by the freezer control temperature. A small portion of the evaporator air circulation flows through the fresh food compartment and compartment temperatures are balanced according to the freezer temperature settings during the post-compressor cycle fan control. The temperature control set points to operate the compressor and fan are based on algorithms that compensate the control for the combination of freezer and fresh food temperature settings.