Abstract: An apparatus for measuring an operating parameter of a relay armature operating a pair of relay contacts, and for controlling the voltage that occurs between the pair of relay contacts when they open or close. The apparatus includes a microcontroller that senses a reference voltage, and a sensed voltage signal that comprises a voltage component representing a relay coil voltage, a power supply voltage component, and a voltage component induced by a motion of the armature. The microcontroller uses discrete digital samples of the signals to deduce the operating parameter. The microcontroller provides a control signal to cause the relay to open or close the relay contacts at a time when a predefined voltage occurs therebetween. The predefined voltage can be substantially zero volts. Methods of use of the apparatus to control the opening and closing of relay contacts are described.

Abstract: A refrigerated device having a cooled enclosure and an evaporator through which refrigerant is circulated. An air temperature sensor adapted to generate an air temperature signal indicative of air temperature within the enclosure is provided. A refrigerant temperature sensor adapted to generate a refrigerant temperature signal indicative of refrigerant temperature is provided. A programmable controller adapted to compare the air temperature signal and the refrigerant temperature signal to calculate a difference between the air temperature and the refrigerant temperature is provided. The controller initiates a defrost routine for removing condensate from the evaporator if the difference between the air temperature and the refrigerant temperature is greater or equal to a defrost threshold. Also disclosed are methods for defrosting a refrigerated device and for detecting condensate accumulation.