Abstract: An event detector and associated methods of protecting systems provide convenient and economical safety features. In a described embodiment, an ignition sequence detector for a boiler system has a microprocessor which is programmed so that an ignition control module of the boiler system is deprived of primary power when an improper sequence of events occurs. The ignition sequence detector includes multiple event detectors interconnected to the microprocessor, and is configured so that it is usable in high RFI environments.

Abstract: An event detector and associated methods of protecting systems provide convenient and economical safety features. In a described embodiment, an ignition sequence detector for a boiler system has a microprocessor which is programmed so that an ignition control module of the boiler system is deprived of primary power when an improper sequence of events occurs. The ignition sequence detector includes multiple event detectors interconnected to the microprocessor, and is configured so that it is usable in high RFI environments.

Abstract: An event detector and associated methods of protecting systems provide convenient and economical safety features. In a described embodiment, an ignition sequence detector for a boiler system has a microprocessor which is programmed so that an ignition control module of the boiler system is deprived of primary power when an improper sequence of events occurs. The ignition sequence detector includes multiple event detectors interconnected to the microprocessor, and is configured so that it is usable in high RFI environments.

Abstract: An ballast includes a variable frequency boost circuit and a driven half-bridge inverter having a series resonant, direct coupled, parallel output. A control circuit includes a variable frequency driver section, a multivibrator section, and a sensing section. The variable frequency driver changes frequency smoothly, i.e. without discontinuities. The multivibrator section acts as a switch that is enabled or disabled by the sensing section for controlling the frequency of the inverter. Lamp current is required for continued operation of the control circuit. The multivibrator section controls starting by causing the inverter to produce an output signal having a trapezoidal envelope. In the event of an arc, the control circuit quenches the arc and the multivibrator periodically pulses the lamp to attempt to re-start the lamp.

Abstract: An instant start ballast includes a variable frequency boost circuit and a driven half-bridge inverter having a series resonant, direct coupled, parallel output. A control circuit includes a variable frequency driver section, a multivibrator section, and a sensing section. The variable frequency driver changes frequency smoothly, i.e. without discontinuities. The multivibrator section acts as a switch that is enabled or disabled by the sensing section for controlling the frequency of the inverter. Lamp current is required for continued operation of the control circuit. The multivibrator section controls starting by causing the inverter to produce an output signal having a trapezoidal envelope. In the event of an arc, the control circuit quenches the arc and the multivibrator periodically pulses the lamp to attempt to re-start the lamp.

Abstract: An electronic ballast for a gas discharge lamp includes an AC to DC converter for changing alternating current at power line voltage to direct current and an inverter powered by the converter and having a series resonant, direct coupled output coupled to the lamp. The inverter includes an AC switch having a diode bridge defining an AC diagonal and a DC diagonal and a transistor connected across the DC diagonal. The primary winding of a filament transformer is connected across the AC diagonal of the bridge and the transistor is coupled to the microprocessor for controlling current through the primary winding. The microprocessor is programmed to close the AC switch while the lamp is starting and to open the switch after the lamp is started, thereby cutting off the filaments from a source of power and reducing the power consumed by the ballast during normal operation. A resistor in series with the transistor is used to detect filament resistance and provide an indication of lamp type.

Abstract: A microprocessor controlled, electronic ballast operates a lamp at nominal settings and shifts the operation of the ballast away from nominal settings to reduce interference. The shift is randomized by a test--flip--?shift! routine that prevents all ballasts from attempting the same correction at the same time. On DC input voltage, the frequency of the boost controller is varied to reduce EMI. The ballast operates in bands according to the input voltage. Some bands correspond to full brightness, some to a fixed amount of dimming, and some to a variable amount of dimming. In the event of an abrupt change in load, the microprocessor changes the frequency of the inverter, thereby reducing output power and gradually unloading the boost circuit and maintaining power to the microprocessor.

Abstract: An electronic ballast includes an AC to DC converter for power factor correction, a bulk capacitor for storing energy from the converter, and a microprocessor controlled, half-bridge inverter including a series resonant, direct coupled output. Input ports of the microprocessor are coupled to several locations within the ballast to monitor the operation of the ballast or the operation of a gas discharge lamp coupled to the ballast. An analog voltage limiter overrides the microprocessor to limit output voltage under fault conditions. A storage capacitor, connected in series with the bulk capacitor, stores energy at low voltage for powering the microprocessor. The microprocessor is programmed to provide lamp protection features, lumen maintenance, and a warm-up period for a lamp. The microprocessor is also programmed to meet the operating requirements of world markets and of different lamp types.

Abstract: An electronic ballast includes a series resonant inductor and capacitor and a filament winding magnetically coupled to said inductor. The filament winding forms a closed circuit with a filament in a gas discharge lamp, wherein the current induced in the winding opposes a portion of the current through the inductor to reduce the net voltage on the filament during normal lamp operation. In accordance with another aspect of the invention, the filament winding is reversely wound with the inductor on a common core to reverse the phase of the current induced in the filament winding from the current through the inductor.

Abstract: A receiver circuit and method for receiving a signal having a given carrier frequency. The circuit comprises: (1) a solar cell receiver having a selected capacitance and (2) an inductive device having a selected inductance and coupled to the solar cell receiver, the solar cell receiver and the inductive device cooperating to form a resonant circuit having a selected resonant frequency associated therewith and being a function of the selected capacitance and the selected inductance, the resonant circuit resonating in response to a change in the signal to thereby allow the solar cell to receive data carried by the signal. By employing solar cell as part of a resonant circuit, the range of optical remote controls can be extended to as much as a mile. In one embodiment, the receiver circuit forms a portion of a remote-controlled pool or spa.

Abstract: A tub is supplied with hot water through a water circulation system including a pump, a water filter and an electric flow-through heater energized through an electric contactor upon closure thereof. A user of the tub is urged to service the water circulation system upon clogging thereof. For this purpose, water flow fluctuations occurring in the circulation system upon restriction of the water circulation system are sensed and closure of the contactor is precluded for a time interval of predetermined duration in response to a sensing of water flow fluctuations.

Abstract: An electronic temperature control circuit is disclosed for use with swimming pool and spa heaters. The circuit employs a thermistor for sensing water temperature, and provides temperature control with a narrow differential. Safety circuits are also employed to prevent injury to the user or to the heater in the event of a component failure. The temperature control circuit is provided with means for presetting two desired temperature settings and for selecting one of the preset temperature settings for control. Remote control circuits are also disclosed for use with the temperature control circuit which permit temperature selection, temperature setting and a visual indication of heater status from a location remote from the heater.

Abstract: An electronic temperature control circuit is disclosed for use with swimming pool and spa heaters. The circuit employs a thermistor for sensing water temperature, and provides temperature control with a narrow differential. Safety circuits are also employed to prevent injury to the user or to the heater in the event of a component failure. The temperature control circuit is provided with means for presetting two desired temperature settings and for selecting one of the preset temperature settings for control. Remote control circuits are also disclosed for use with the temperature control circuit which permit temperature selection, temperature setting and a visual indication of heater status from a location remote from the heater.

Abstract: The temperatures at the inlet and the outlet of a solar energy collector being flown through by water are detected and compared with a ramp signal to provide a pulse train in which the number of pulses represents the temperature differential. The ramp signal is produced at a repetition rate representing the water flow rate so that the tallied pulses represent the BTU's as absorbed by the collector.