How PLC works?
PLC means programmable logic controller …. it consists basically of 3 main parts which are the input (connected to the sensors), the memory (where the program is stored) and the output (action taken from a decision taken by the manager). the PLC normally scans the memory at 100 ms (milliseconds) to detect any change of state of the input, checks the program registered for the action to be executed (output) for this input state ….
The main function of a PLC is to control a process using feedback devices and actuators.
The operating principle of PLC is simple.
it analyzes the state / state of the inputs (which are connected to sensors, pushbuttons, safety devices, etc.)
, then the logic / program stored in its memory is processed. the logic is usually made in relay language that is based on relay schemas, but there are also other languages, such as fbd (block diagram, a person of electronics will follow it easily).
Next, the status of the outputs is updated according to the program. and these three steps take place in a scan cycle, and that is how the PLC works.
but, all this is after wiring and installation. for wiring and installation, you need to know how the control wiring works and, depending on the sensors and the type of PLC, what kind of cabling should be followed, depending on the type of supply.
This is basic information about how a plc works.
plc stands for programmable logic controller.
plc is a hardware that is in fact a foolproof micro-controller system with ready-to-use input and output.
inside a PLC, there are several smart relay modules and timer circuits with protection circuits. The microcontroller is designed to perform certain tasks in a specified manner.
An important factor in plc is the analysis time. This is the time during which the controller of the PLC executes a line. It is divided into three parts: scan the entries, execute the logic and update the outputs.
apart from this plc has a memory unit which essentially comprises digital circuits called transistors. this memory is used to store the program. moreover, part of this memory is reserved for use as virtual bits / tags. these bits are used to store temporary data or the state of the inputs / outputs.
thus, the PLC starts by scanning all the inputs / outputs, executes the logic and updates the internal bits and i / os.