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Answer the following questions in respect of PLCs. - NSC Electrical Technology Electronics - Question 7 - 2017 - Paper 1
Question 7
Answer the following questions in respect of PLCs.
Worked Solution & Example Answer:Answer the following questions in respect of PLCs. - NSC Electrical Technology Electronics - Question 7 - 2017 - Paper 1
Step 1
Step 2
List the main components of a PLC.
Answer
The main components of a PLC include:
- Power Supply - Provides the necessary power to the PLC.
- Central Processing Unit (CPU) - The brain of the PLC where the logic is processed.
- Input/Output Modules - Facilitates communication between the PLC and field devices.
- Programming Device - Used to program and configure the PLC.
- Communication Interface - Allows the PLC to communicate with other PLCs or devices.
Step 3
Explain how a PLC operates.
Answer
A PLC operates by continuously cycling through a series of steps:
- Input Scan - The PLC reads the status of input devices (e.g., sensors, switches).
- Program Execution - The PLC executes the program stored in its memory based on the input states.
- Output Scan - The PLC updates the state of output devices (e.g., motors, lights) accordingly.
- Housekeeping - The PLC performs diagnostic checks and updates internal data. This cycle repeats continuously.