- What is the method used by the plc to write a ladder logic program is called software#
- What is the method used by the plc to write a ladder logic program is called series#
So if you can understand how basic electrical circuits work then you can understand ladder logic. The rungs represent the wiring between the different components which in the case of a PLC are all in the virtual world of the CPU. The left and right rails indicate the positive and ground of a power supply. The completed program looks like a ladder but in actuality it represents an electrical circuit. Over the years the number of symbols has increased to provide a high level of functionality. These symbols are interconnected by lines to indicate the flow of current through relay like contacts and coils. Ladder logic uses symbols, instead of words, to emulate the real world relay logic control, which is a relic from the PLC's history. The most widely used form of programming is called ladder logic.
What is the method used by the plc to write a ladder logic program is called software#
In these modern times a PC with specially dedicated software from the PLC manufacturer is used to program a PLC. Typical outputs signals can range from 0-10 VDC or 4-20mA and are used to drive mass flow controllers, pressure regulators and position controls. An analog output card will convert a digital number sent by the CPU to it’s real world voltage or current. A digital output card either turns a device on or off such as lights, LEDs, small motors, and relays. Output devices can also consist of digital or analog types. Examples of analog devices are pressure transducers, flow meters and thermocouples for temperature readings a signal that can be anywhere from 0 to 20mA) into a digitally equivalent number that can be understood by the CPU. An analog input card converts a voltage or current (e.g. A digital input card handles discrete devices which give a signal that is either on or off such as a pushbutton, limit switch, sensors or selector switches. Input devices can consist of digital or analog devices. It’s called “modular” because the rack can accept many different types of I/O modules that simply slide into the rack and plug in. For our consideration, we’ll look at the more modular rack based systems. “bricks”) are typically designed with fixed I/O points.
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They can be so small as to fit in your shirt pocket while more involved controls systems require large PLC racks. The components that make a PLC work can be divided into three core areas. Unlike a personal computer though the PLC is designed to survive in a rugged industrial atmosphere and to be very flexible in how it interfaces with inputs and outputs to the real world. It therefore shares common terms with typical PCs like central processing unit, memory, software and communications. So it is time, labor and money for any little change.Ī programmable logic controller is a specialized computer used to control machines and processes. If your boss came along and said I want that light to turn on thirty seconds after the switch has been flipped, then you would need to buy a timer and do some rewiring. Beyond that though there is no more control.
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In this system with a flick of the switch the light would turn on or off. A Simple ExampleĬonsider something as simple as a switch that turns on a light. They are meant to be very flexible in how they can be programmed while also providing the advantages of high reliability (no program crashes or mechanical failures), compact and economical over traditional control systems.
What is the method used by the plc to write a ladder logic program is called series#
The basic units have a CPU (a computer processor) that is dedicated to run one program that monitors a series of different inputs and logically manipulates the outputs for the desired control. Where ever there is a need to control devices the PLC provides a flexible way to "softwire" the components together. They are used in many industries such as oil refineries, manufacturing lines, conveyor systems and so on.
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A Programmable Logic Controller, or PLC for short, is simply a special computer device used for industrial control systems.