6.1 Explain the term program when referring to a PLC - NSC Electrical Technology Electronics - Question 6 - 2017 - Paper 1
Question 6
6.1 Explain the term program when referring to a PLC.
6.2 What do the letters PLC represent?
6.3 Name THREE basic devices used in programming a PLC.
6.4 With r... show full transcript
Worked Solution & Example Answer:6.1 Explain the term program when referring to a PLC - NSC Electrical Technology Electronics - Question 6 - 2017 - Paper 1
Step 1
Explain the term program when referring to a PLC.
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Answer
A program in the context of a PLC (Programmable Logic Controller) refers to a series of instructions written in a specific programming language that the PLC can recognize and interpret in order to take actions or produce outputs based on given inputs. It essentially dictates how the PLC operates and responds to various inputs.
Step 2
What do the letters PLC represent?
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Answer
PLC stands for Programmable Logic Controller.
Step 3
Name THREE basic devices used in programming a PLC.
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User Interface (like buttons and screens on the PLC unit).
Computer or laptop with an interface cable.
Handheld programming device.
Step 4
With reference to an OR-gate, draw the following: The circuit diagram, using two switches and a lamp to simulate the gate operation.
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To draw the OR-gate circuit diagram, depict two switches (labeled Switch A and Switch B) connected in parallel to a lamp. The output is linked to the lamp, such that when either Switch A or Switch B is closed, the lamp will light up.
Step 5
With reference to an OR-gate, draw the following: The ladder logic diagram.
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In the ladder logic diagram, represent the OR operation using two parallel branches. Each branch corresponds to one switch. Connect the lamp at the end of the branches, which indicates that if either switch is activated, the lamp will turn on.
Step 6
Name THREE programming languages used in programming PLCs.
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Ladder Logic (IL)
Structured Text
Function Block Diagram
Step 7
Simplify the expression below by using Boolean algebra: \( \overline{A}BC + ABC + \overline{A}C + ABC \)
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Starting with the expression:\n( \overline{A}BC + ABC + \overline{A}C + ABC )
Recognizing repetitive terms, we simplify:\n1. Combine terms: ( \overline{A}BC + ABC + \overline{A}C = BC(A + \overline{A}) + B )\n2. Apply the Complement Law: ( A + \overline{A} = 1 ) \Rightarrow ( B + BC )\n3. Thus simplified form is: ( B + C )
Step 8
Explain why the maintenance of a PLC system (soft-wired system) should be less than that of a relay system (hard-wired system).
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Maintenance of a PLC system is generally less intensive as it utilizes software configurations rather than physical connections. Components are less prone to wear and tear compared to hard-wired components like contacts in relay systems. Additionally, PLC systems often incorporate built-in diagnostic functions that can quickly identify issues, further simplifying maintenance.
Step 9
Write down the Boolean equation of the control system.
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The Boolean equation for the control system can be expressed as: ( F = A \cdot B + A \cdot C + B \cdot C ), where F represents the output which is activated when two or more sensors are triggered.
Step 10
Simplify the equation using a Karnaugh map.
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Using a Karnaugh map for the equation ( F = A \cdot B + A \cdot C + B \cdot C ), identify groups of '1's and simplify to get the minimized expression, which may result in a simplified form like ( F = B + C ).
Step 11
Draw the gate network of the simplified system.
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The gate network can consist of an OR gate that takes inputs from sensor A, B, and C, signalling that the output F will activate when at least two sensors are in a 'high' state (1).
