Abstract: A rack mountable weld controller for use as a plug in card within a rack of a programmable logical controller (PLC) system. All signals between the PLC and the weld controller are through the backplane of the rack in which the weld controller is installed. In this manner, the large number of signals which are needed to operate the weld controller may be passed through the backplane rather than over a set of cables connecting the weld controller to an input card and output card which are themselves plugged into a backplane slot.

Abstract: An intelligent compiler particularly useful for evaluating Boolean expressions such as those associated with ladder structures. True/false paths are defined through the expressions. In a first pass for the code generation, the start code for examining each element is set out. In a second pass the relative offsets for branching from one element to the next element along both the true and false paths are filled in. In practice, execution time for evaluating ladder structures is reduced by an order of magnitude over prior techniques which use source code and an interpreter.

Abstract: A system is provided for use in a microprocessor controlled controller for a resistance welding machine for calculating the RMS value of the welding current so as to provide a closed loop control of the RMS current in order to eliminate the effect of variations in load and line voltage on the welding current and to provide a constant welding tip temperature in the presence of such variations.

Abstract: A precision key pad controlled controller for a resistance welding machine is provided which may be set to deliver welding power to each of a multiplicity of welding operations on a precisely controlled repeatable basis. The controller incorporates circuitry for assuring that an accurately controlled amount of power is delivered for each welding operation by providing precise phase angle control despite variations in line voltage and line disturbances. The controller is constructed to incorporate selected numbers of steps to be performed automatically in sequence by the controlled welding machine in carrying out a particular welding operation. The duration of each step of the welding machine, the amount of welding power to be delivered, and other parameters are set for each particular welding operation by the key pad, and displayed on an associated alphanumeric display.

Abstract: A control system for use with a welding machine controller is provided which senses the dynamic resistance of the weld being formed by the welding machine, and which generates appropriate signals indicating the condition of the weld, which signals may be used for automatically controlling the operation of the controller. The control system of the invention senses the power factor in the primary circuit of the welding transformer included in the welding machine which is a measure of the dynamic resistance of the weld being formed, and the control system produces signals indicating the dynamic resistance of the weld, which signals may be digitized to produce appropriate control signals for the controller.

Abstract: A precision resistance welding machine controller is provided which may be set to deliver welding power to each of a multiplicity of welding operations on a precisely controlled repeatable basis. The controller of the invention is modular in nature and is microprocessor controlled. The controller includes a master control module which is standard for all models, and the master control module incorporates certain control circuits including a circuit for assuring that an accurately controlled amount of power is delivered for each welding operation. This is achieved by providing precise phase angle control despite variations in line voltage, and line noise disturbances. The controller also includes a personality module which is constructed for a particular welding operation, and which is programmed to incorporate any selected number of steps to be performed in sequence by the welding machine controlled thereby in carrying out the particular welding operation.

Abstract: An interface circuit is provided for interconnecting an electronic controller to a contactor circuit which, in turn, controls the alternating current flow from an alternating current power source to controlled equipment, such as a resistance welding machine. The contactor circuit, for example, includes a pair of semiconductor switching devices, such as silicon controlled rectifiers (SCR)s, the two semiconductor switching devices are alternately rendered conductive during successive half-cycles of the alternating current power from the alternating current power source at times controlled by the controller for the controlled operation of the welding machine. The interface circuit includes means for monitoring the junction temperature of each of the semiconductor switching devices, and to provide an indication and a control effect should the junction temperature exceed a particular safe threshold.

Abstract: An operating circuit for a semiconductor switch device of the type that passes electrical current from a source to an electrical load by forward biasing of the semiconductor's control terminal includes a resistance bridge network having in an arm thereof the control terminal to one main terminal circuit of the semiconductor switch, and a bias control for alternately applying forward bias and reverse bias to the control terminal through the bridge network, whereby a voltage is developed across the bridge output during the interval in which the control terminal is reverse biased that is representative of the junction temperature within the semiconductor. The temperature representative voltage is observed, monitored, and used for indication and control.