6.1 Identify THREE programming methods used in programmable logic controllers (PLCs). 6.2 Name TWO INPUT devices that may be connected to the input stage of a PLC. 6.3 State THREE disadvantages of a hardwired system in comparison with a PLC system. 6.4 Explain how low-current devices, such as transistors, may be activated by the output of a PLC. 6.5 Write the simplified Boolean equation for the expression below. Use a four-variable Karnaugh map. X = AB + A'B'C + AB'C + ABCD + AB'CD + AB + BCD 6.6 Simplify the following Boolean equation by using Boolean algebra. Q = AB'C + ABC + AB + A. 6.7 Refer to FIGURE 6.1. Determine the output at the following points: 6.7.1 W 6.7.2 X 6.7.3 Y 6.7.4 Z 6.8 Name the following ladder logic symbols: 6.8.1 6.8.2 6.8.3 6.9 Refer to FIGURE 6.2 and answer the questions that follow. 6.9.1 Draw the ladder logic diagram that will execute the same function in a PLC system. 6.9.2 Give ONE example where the circuit in FIGURE 6.2 may be used in an electrical application.

NSC Electrical Technology Power Systems PLC Applications: 6.1 Identify THREE programming m

6.1 Identify THREE programming methods used in programmable logic controllers (PLCs) - NSC Electrical Technology Power Systems - Question 6 - 2016 - Paper 1

Question 6

6.1 Identify THREE programming methods used in programmable logic controllers (PLCs). 6.2 Name TWO INPUT devices that may be connected to the input stage of a PLC. ... show full transcript

Worked Solution & Example Answer:6.1 Identify THREE programming methods used in programmable logic controllers (PLCs) - NSC Electrical Technology Power Systems - Question 6 - 2016 - Paper 1

Step 1

6.1 Identify THREE programming methods used in programmable logic controllers (PLCs).

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Answer

Relay Ladder Logic (RLL)
Structured Text (ST)
Function Block Diagram (FBD)

Step 2

6.2 Name TWO INPUT devices that may be connected to the input stage of a PLC.

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Answer

Push Button Switch
Limit Switch

Step 3

6.3 State THREE disadvantages of a hardwired system in comparison with a PLC system.

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Limited flexibility: Changes in the design require extensive rewiring.
Difficulty in Troubleshooting: Hardwired systems can be challenging to diagnose and repair.
Increased downtime: Modifications or repairs to a hardwired system can lead to longer downtimes.

Step 4

6.4 Explain how low-current devices, such as transistors, may be activated by the output of a PLC.

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Answer

Low-current devices can be activated by utilizing the output relay of a PLC, which delivers voltage via a transistor. This allows for the control of high-current and high-voltage devices without directly interfacing them with the PLC.

Step 5

6.5 Write the simplified Boolean equation for the expression below. Use a four-variable Karnaugh map.

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Answer

Using the Karnaugh map for the function:
$X = AB + A'B'C + AB'C + ABCD + AB'CD + AB + BCD$
The simplified equation is: $X = AB + CD$

Step 6

6.6 Simplify the following Boolean equation by using Boolean algebra.

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For the equation:
$Q = AB'C + ABC + AB + A$
Applying Boolean algebra:

Combine terms: $Q = A(B'C + BC + B) + A$
Apply Consensus theorem: $Q = A + B'C$

Step 7

6.7 Refer to FIGURE 6.1. Determine the output at the following points.

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6.7.1 W: $W = A + B$ 6.7.2 X: $X = A + C$ 6.7.3 Y: $Y = A.B$ 6.7.4 Z: $Z = (A + B)(A + C)(A.B)$

Step 8

6.8 Name the following ladder logic symbols.

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6.8.1 Normally open contact / switch (Input) 6.8.2 Normally closed contact (Input) 6.8.3 (Coil) output (Output)

Step 9

6.9.1 Draw the ladder logic diagram that will execute the same function in a PLC system.

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The ladder logic diagram would consist of:

Start push button connected to the coil of the relay.
Normally open contact in series with the Start button.
A holding contact parallel to the Start button.

Step 10

6.9.2 Give ONE example where the circuit in FIGURE 6.2 may be used in an electrical application.

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Answer

An example would be its use in a motor starter circuit, which controls the starting and stopping of an electric motor.

6.1 Identify THREE programming methods used in programmable logic controllers (PLCs) - NSC Electrical Technology Power Systems - Question 6 - 2016 - Paper 1

Worked Solution & Example Answer:6.1 Identify THREE programming methods used in programmable logic controllers (PLCs) - NSC Electrical Technology Power Systems - Question 6 - 2016 - Paper 1

6.1 Identify THREE programming methods used in programmable logic controllers (PLCs).

6.2 Name TWO INPUT devices that may be connected to the input stage of a PLC.

6.3 State THREE disadvantages of a hardwired system in comparison with a PLC system.

6.4 Explain how low-current devices, such as transistors, may be activated by the output of a PLC.

6.5 Write the simplified Boolean equation for the expression below. Use a four-variable Karnaugh map.

6.6 Simplify the following Boolean equation by using Boolean algebra.

6.7 Refer to FIGURE 6.1. Determine the output at the following points.

6.8 Name the following ladder logic symbols.

6.9.1 Draw the ladder logic diagram that will execute the same function in a PLC system.

6.9.2 Give ONE example where the circuit in FIGURE 6.2 may be used in an electrical application.

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