Abstract: An air flow sensor including a temperature dependent resistor device, a first circuit and a second circuit. The first circuit applies a voltage to the temperature dependent resistor device until it reaches a first temperature. The first circuit includes a first reference resistance leg, a first variable resistance leg including the temperature dependent resistor device, and a first comparator connected to both legs for determining when the temperature dependent resistor device reaches the first temperature. The second circuit includes a second reference resistance leg, a second variable resistance leg including the temperature dependent resistor device, and a second comparator connected to both legs for determining when the temperature dependent resistor device reaches a second temperature.

Abstract: A thermal management system for an enclosure housing devices which generate heat inside the enclosure. A fan, whose speed is responsive to an input signal, has a gas flow output in communication with the enclosure. A filter is disposed in the gas flow path of the fan's output. At least one temperature sensor is disposed in the enclosure for measuring the temperature inside the enclosure. A controller adjusts the speed of the fan until the temperature inside the enclosure is within a predetermined range to ensure that the devices inside the enclosure do not overheat. A processor compares the signal input to the fan with the speed of the fan to determine the condition of the fan and, in response to the temperature sensor, determines the condition of the filter.

Abstract: A pulse width modulated inductive load controller including a load switching circuit having a plurality of switches which are operative in pairs; each pair including first and second switch devices for controlling power to a load. Commutation logic enables various sequential combination of pairs of switch devices and a clock defines the operation period of each sequential combination of switch device pairs. Pulse width modulation circuitry controls the closed time interval of the switch devices during the operation period of each combination of switch device pairs. Transition control circuitry maintains closed at least one of the switch devices in each sequential combination of switch device pairs after the other switch device is opened, thereby assuring that any regenerated current from the previously energized load coils is provided a path to recirculate through the load.