Search results
Results from the WOW.Com Content Network
A PLC is an industrial microprocessor-based controller with programmable memory used to store program instructions and various functions. [21] It consists of: A processor unit (CPU) which interprets inputs, executes the control program stored in memory and sends output signals, A power supply unit which converts AC voltage to DC,
A Voltage controller thyristor based dimmer rack An electrical schematic for a typical SCR-based light dimmer. A voltage controller, also called an AC voltage controller or AC regulator is an electronic module based on either thyristors, triodes for alternating current, silicon-controlled rectifiers or insulated-gate bipolar transistors, which converts a fixed voltage, fixed frequency ...
In 1978, Opto 22 developed the first computer-based plug-in I/O modules, and created the Yellow-Black-White-Red color scheme used to identify digital AC input, digital AC output, digital DC input, and digital DC output modules respectively. In 1982, the company created Optomux, a serial-based I/O system using the ASCII protocol.
A feedback control loop is directly controlled by the RTU or PLC, but the SCADA software monitors the overall performance of the loop. For example, a PLC may control the flow of cooling water through part of an industrial process to a set point level, but the SCADA system software will allow operators to change the set points for the flow.
HVAC (Heating, Ventilation and Air Conditioning) equipment needs a control system to regulate the operation of a heating and/or air conditioning system. [1] Usually a sensing device is used to compare the actual state (e.g. temperature) with a target state.
Siemens SIMATIC S7-300 PLC CPU with three I/O modules attached. As with other programmable logic controllers, SIMATIC devices are intended to separate the control of a machine from the machine's direct operation, in a more lightweight and versatile manner than controls hard-wired for a specific machine. Early SIMATIC devices were transistor ...
IEC 61131-3 is the third part (of 10) of the international standard IEC 61131 for programmable logic controllers.It was first published in December 1993 [1] by the IEC; the current (third) edition was published in February 2013.
Standard IEC 61131 is divided into several parts: [3]. Part 1: General information. It is the introductory chapter; it contains definitions of terms that are used in the subsequent parts of the standard and outlines the main functional properties and characteristics of PLCs.