Abstract: The control system for a humidifier, which is part of a heat, ventilation or air conditioning HVAC system, detects the level of water and generates control signals by detecting the capacitance of the water in the humidifier. These control signals are used to fill the humidifier with water and control heater elements and, to some degree, drain cycles. A capacitor is utilized to detect the change in capacitance as the water level changes. The control circuit, coupled to the capacitor, generates fill control signals based upon first and second predetermined capacitive levels. In one embodiment, the capacitor sensor includes an electrically conductive element extending into the water as a first electrode which is shielded by an insulating cover, where the water acts as a medium through which capacitance is measured and the humidifier casing or another electrically conductive element in the water functions as the second electrode for the capacitor.

Abstract: The microprocessor based controller for the fractional horsepower actuator motor includes a capacitive power backup system. The motor is used as an actuator and is coupled to an air damper or valve. In the event of a loss of power to the controller, the controller must drive the air damper or valve to a predetermined, failsafe position. The capacitive energy source stores sufficient power to drive the motor and the coupled air damper or valve to the predetermined failsafe position. The controller includes a sensor for determining the presence or absence of power and generating a failsafe control signal. A switch receives the failsafe control signal and passes power from either the main power supply or the capacitive energy storage unit. The controller includes a microprocessor and a memory. During a failsafe operation, the microprocessor drives the motor and hence the air damper or valve to the failsafe position at full power.

Abstract: The air velocity detector is used in combination with an air duct carrying heat, ventilation or air conditioned (HVAC) air therethrough. A rigid support subassembly is mounted in the HVAC air duct. At least a pair of ultrasonic transceivers are mounted in a spaced apart relationship facing each other on opposing end portions of the support subassembly. The acoustic, ultrasonic signal path from one transceiver to the other diagonally extends across a volume of duct covered by the rigid support subassembly. In one embodiment, the subassembly is a rigid sleeve mounted to the inboard, interior portions of the duct. In another embodiment, the subassembly is a rigid, substantially straight member diagonally extending through the duct volume. Electronic circuitry is connected to the transceivers which excites the transceivers, processes the received ultrasonic signal, and determines the phase difference or phase difference between the transmitted ultrasonic signal and the received ultrasonic signal.

Abstract: The emergency, fail safe capacitive energy source and circuit is used in conjunction with an air damper actuator or a valve actuator. In particular, the capacitive energy source and circuit powers a fractional horsepower motor and both the motor as well as the capacitive energy source and circuit are completely contained within an actuator container of a relatively small size. The capacitive energy source and circuit include at least one high storage capacitor (rated 0.047 farads or higher) having a volumetric size not exceeding 30 cubic inches. Preferably, a bank of high value capacitors are utilized wherein the capacitors are coupled in series or parallel to power the AC or DC motor and associated circuitry. The capacitive energy source and circuit also includes a charging circuit coupled between the motor drive power source and the capacitor or bank of capacitors. A sensor is coupled to the motor drive power source and generates a control signal in the absence of power from the motor drive power source.