QUESTION 7: PROGRAMMABLE LOGIC CONTROLLERS (PLCs)
7.1 Explain the advantages of PLC systems with regard to the following:
7.1.1 Space
7.1.2 Flexibility
7.2 FIGURE 7.2 below shows the ladder logic of a logic gate - NSC Electrical Technology Power Systems - Question 7 - 2023 - Paper 1
Question 7
QUESTION 7: PROGRAMMABLE LOGIC CONTROLLERS (PLCs)
7.1 Explain the advantages of PLC systems with regard to the following:
7.1.1 Space
7.1.2 Flexibility
7.2 FIGUR... show full transcript
Worked Solution & Example Answer:QUESTION 7: PROGRAMMABLE LOGIC CONTROLLERS (PLCs)
7.1 Explain the advantages of PLC systems with regard to the following:
7.1.1 Space
7.1.2 Flexibility
7.2 FIGURE 7.2 below shows the ladder logic of a logic gate - NSC Electrical Technology Power Systems - Question 7 - 2023 - Paper 1
Step 1
7.1.1 Space
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Answer
PLC systems significantly reduce the need for physical relays and switching devices that take up space. By integrating various functions into a single unit, PLCs minimize the physical footprint required for control systems.
Step 2
7.1.2 Flexibility
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PLCs offer great flexibility as modifications can easily be made without replacing wired connections or hardware components. This allows for quick adjustments in logic and control without requiring extensive rewiring.
Step 3
7.2.1 Name the logic gate represented in FIGURE 7.2 above.
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The logic gate represented in FIGURE 7.2 is a NOR gate.
Step 4
7.2.2 Draw the equivalent logic gate symbol of FIGURE 7.2.
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The equivalent logic gate symbol for a NOR gate can be drawn as follows:
___
A | |
|NOR|---- Output
B |___|
Step 5
7.2.3 Complete the truth table in FIGURE 7.3 by writing only the state of the output.
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Answer
From the input states, we have:
For A = 0 and B = 0, the output (W) is 1 (since both inputs are low in a NOR gate).
For A = 0 and B = 1, the output (X) is 0 (as one input is high).
Thus, the states are:
A B OUTPUT
0 0 1
0 1 0
Step 6
7.3.1 Name the type of proximity sensor that utilises an electrostatic field (e-field) to sense proximity.
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The type of proximity sensor that utilizes an electrostatic field is called a capacitive proximity sensor.
Step 7
7.3.2 Describe the purpose of a light sensor in an automated garage door.
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A light sensor in an automated garage door serves as a safety feature. It detects interruptions in the beam of light and ensures that the door does not close when an object is in the way, thereby preventing accidents.
Step 8
7.3.3 Explain how a temperature sensor is used to prevent a dangerous condition from breaking.
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A temperature sensor monitors the environment for temperature changes. If it detects that a temperature exceeds a predetermined threshold, it can trigger an alarm or shut down the device to prevent overheating and potential damage or hazards.
