Abstract: A phase control system has a stable timebase phase reference generated by an internal phase reference generator. The control includes a method for estimating and compensating phase distortion when an inductive load is driven by an AC voltage source having significant line impedance. A digital phase comparator estimates a phase error between the timebase phase reference and the voltage source. At the initialization of the phase control system, the phase reference clock period is frozen for a fixed number of cycles to determine an average phase error due to the phase distortion caused by the line impedance. The estimated phase error is then corrected to account for the average phase distortion error.

Abstract: A phase controlled weld controller system provides a stable timebase phase reference which has improved transient response in the presence of spurious noise generated by other external equipment coupled to the same voltage source. The system estimates a phase error between an internal phase reference generator and the voltage source. The system also estimates the phase distortion generated by the weld control when operating with an inductive impedance load when significant line impedance is present. The weld controller provides compensation for the phase distortion in the timebase phase reference using the estimated line impedance to realize a phase reference which more accurately tracks the voltage source.

Abstract: A phase control system has a stable timebase phase reference generated by an internal phase reference generator which has improved transient response in the presence of spurious noise generated by other external equipment coupled to the same voltage source. A digital phase comparator estimates a phase error between the timebase phase reference and the voltage source. The internal phase reference generator constructs the timebase using a normalized difference between the volt-time-areas between two adjacent quadrants of the internal timebase phase reference. This allows corrections to the phase reference generator to be made on the next cycle of the phase reference generator based on the error estimate of the present cycle.

Abstract: A weld controller utilizing a constant current control employs a stepper program for increasing current boost in predetermined percentage increments or steps following a predetermined stepper current profile to provide compensation for contact tip wear. The weld controller acquires weld power data in the form of current and voltage samples for each step of the stepper program, and computes Volt Amperes or power from this data during an acquisition run through the stepper program. The stepper program specifies a constant current at each step. Associated with each incremental current step, weld power that is required to produce that weld current is determined by the weld controller to generate a characteristic power curve. The power curve will be over the range of currents as specified by the combination of the programmed weld current and the range of current boost as specified by the stepper schedule. The weld controller will build a table of values relating weld current and delivered power or Volt Amperes.

Abstract: A weld controller employs a stepper program for increasing heat boost in one percent increments or steps to provide compensation for contact tip wear. The weld controller acquires weld current data in the form of current samples for each step to create a characteristic curve or nominal current profile for the stepper program. Subsequent operations of the weld control utilize high and low current limit thresholds that track the nominal current profile. The thresholds can be defined as a fixed offset from the profile or as a percentage of the profile at each step of the stepper program. This allows the use of current limits to be established in close proximity to the nominal weld current at all times, enabling the use of tighter tolerances.

Abstract: A communication system between a microprocessor based device and a network of a plurality of remote input/output repeater modules uses a synchronous serial communications protocol. The microprocessor based device contains a transmitter module for generating a data packet containing the status of output device connected to remote input/output repeater modules coupled to the network. A receiver module also contained in the microprocessor based device receives and decodes a returned modified data packet that indicates the status of input devices connected to the same or other remote input/output repeater modules also coupled to the network. The receiver module can detect errors in the returned data packet.

Abstract: A communication system between a microprocessor based device and a network of a plurality of remote input/output repeater modules that control various input and output devices uses a synchronous serial communications protocol. The microprocessor based device contains a transmitter module for generating a data packet that is sent to the remote input/output repeater modules. The transmitter module controls the clock rate of the network and encodes the data packet with an output data byte for each of the repeater modules. The output byte determines the state of the output devices that may be connected to the remote input/output repeater module coupled to the network.

Abstract: A series of remote input/output repeater modules connected on a synchronous serial communication network supervised by a programmable logic controller uses a synchronous serial communications protocol. The programmable logic controller contains a transmitter module for generating a data packet containing the state of output devices connected to the remote input/output repeater modules. A receiver module receives and decodes a returned modified data packet that indicates the state of input devices connected to the same or other remote input/output repeater modules. The remote input/output repeater modules receive and decode the data packet to determine the state of the output devices that may be connected to it and modifies the data packet to indicate the state of its input device if there is one present. The modified data packet is sent to the next in-line remote input/output repeater module coupled to the network.

Abstract: A fail-safe electronically controlled defrost system is provided for use in a frost-free refrigerator suitable for home use. The defrost cycle, in the interests of power conservation, is made subject to plural input electronic control in a circuit in which the intrinsic reliability of the defrost system is specifically designed to revert to a non-power conservation mode in the event of failure of the electronics. Compressor time, door openings and user (vacation mode) settings are typical inputs for control of the period between defrosts.