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Part of a ladder diagram, including contacts and coils, compares, timers and monostable multivibrators. Ladder logic is widely used to program PLCs, where sequential control of a process or manufacturing operation is required. Ladder logic is useful for simple but critical control systems or for reworking old hardwired relay circuits. As ...
The SFC standard is defined as Preparation of function charts for control systems, and was based on GRAFCET (itself based on binary Petri nets [1] [2]). It can be used to program processes that can be split into steps. Basic Batch SFC, with important elements labeled. Main components of SFC are: Steps with associated actions;
Example Ladder Logic Diagram. The schematic diagrams for relay logic circuits are often called line diagrams, because the inputs and outputs are essentially drawn in a series of lines. A relay logic circuit is an electrical network consisting of lines, or rungs, in which each line or rung must have continuity to enable the output device. A ...
Ladder diagram (LD), graphical; Function block diagram (FBD), graphical; Structured text (ST), textual; Instruction list (IL), textual (deprecated in 3rd edition of the standard [3]) Sequential function chart (SFC), has elements to organize programs for sequential and parallel control processing, graphical.
A control loop is the fundamental building block of control systems in general and industrial control systems in particular. It consists of the process sensor, the controller function, and the final control element (FCE) which controls the process necessary to automatically adjust the value of a measured process variable (PV) to equal the value of a desired set-point (SP).
Its name comes from the information path in the system: process inputs (e.g., voltage applied to an electric motor) have an effect on the process outputs (e.g., speed or torque of the motor), which is measured with sensors and processed by the controller; the result (the control signal) is "fed back" as input to the process, closing the loop.
Ladder logic diagrams were developed in response to the increasing complexity of programmable logic devices, but the logic depicted could be implemented in relay logic if one felt the urge. Indeed the start/stop switch example is still often implemented using two push buttons and a relay (or contactor) using exactly the correct logic depicted ...
A motor controller is a device or group of devices that can coordinate in a predetermined manner the performance of an electric motor. [1] A motor controller might include a manual or automatic means for starting and stopping the motor, selecting forward or reverse rotation, selecting and regulating the speed, regulating or limiting the torque, and protecting against overloads and electrical ...