PLC Panel (Programmable Logic Controller Panel):
Programmable Logic Controllers (PLCs) are small industrial computers with modular components designed to automate customized control processes. PLCs are often used in factories and industrial plants to control motors, pumps, lights, fans, circuit breakers and other machinery. Integrated PLC Panel can monitor any process and provide data wherever and however you need it.
There are many components to a PLC, but most of them can be put in the following three categories:
- Processor (CPU)
PLCs are complex and powerful computers; it takes inputs, performs logic on the inputs in the CPU and then turns on or off outputs based on that logic. We can take the following case for example:
1. The CPU monitors the status of the inputs (for example, proximity sensor off, valve 40% open, etc.)
2. The CPU takes the information that it gets from the inputs and performs logic on the inputs
3. The CPU operates the outputs based on the logic (for example, turn off motor, open valve, etc.)
Advantages of PLC control:
- Rugged and designed to withstand vibrations, temperature, humidity, and noise.
- Have interfacing for inputs and outputs already inside the controller.
- Easily programmed and have an easily understood programming language.
Why is PLC Panels:
- Very fast
- Easy to change logic i.e. flexibility
- Reliable due to absence of moving parts
- Low power consumption
- Easy maintenance due to modular assembly
- Facilities in fault finding and diagnostic
- Capable of handling of very complicated logic operations
- Good documentation facilities
- Easy to couple with the process computers
- Analog signal handling and close loop control programming
- Counter, timer and comparator can be programmed
Choosing the correct processor:
For Selecting Modular Processors the most important criteria would be the number of I/O points. Each PLC processor will only be capable of working with a limited number of I/O modules
Another important criteria for selecting processors is Memory size (for data storage or program storage) and Performance (scan time depends on the processor). The size of program is dependent upon the complexity of the control problem and the skill and style of the programmer.
A PLC with an appropriate memory size and speed needs to be selected based on the application.
Programmable Logic Controllers (PLC) Specifications:
|Total Number of Points:||Number of points is the sum of the inputs and the outputs. PLCs may be specified by any possible combination of these values.|
|PLC I/O:||Input/output signals the PLC can accept/Provide|
|Scan Time:||Time required by the PLC to check the states of its inputs and outputs.|
|Data Memory:||Capacity for data storage|
|Program Memory:||Capacity of memory for control software|
|PLC Programming Language:||Ladder Diagram, Structured Text, Relay Ladder Logic, etc|