PLC hardware architecture (CPU, I/O, power supply) in PLC Programming - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define the main PLC component responsible for processing instructions.

PLC Programming

PLC_main_component = "[1]"

Drag options to blanks, or click blank then click option'

AMemory

BPowerSupply

CCPU

DI/O_Module

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing PowerSupply or I/O_Module instead of CPU.

The CPU is the central processing unit of a PLC, handling all instructions and control.

2fill in blank

medium

Complete the code to specify the PLC component that connects sensors and actuators.

PLC Programming

PLC_component_for_external_devices = "[1]"

Drag options to blanks, or click blank then click option'

ACPU

BI/O

CMemory

DPowerSupply

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing I/O with CPU or PowerSupply.

The I/O (Input/Output) modules connect the PLC to sensors and actuators.

3fill in blank

hard

Fix the error in the code to correctly assign the PLC power source.

PLC Programming

PLC_power_source = "[1]"

Drag options to blanks, or click blank then click option'

A"PowerSupply"

B"CPU"

C"I/O"

D"Memory"

Attempts:

3 left

💡 Hint

Common Mistakes

Using CPU or I/O as power source.

The power supply provides electrical power to the PLC system.

4fill in blank

hard

Fill both blanks to create a dictionary representing PLC hardware components and their roles.

PLC Programming

plc_hardware = {"CPU": "[1]", "I/O": "[2]"}

Drag options to blanks, or click blank then click option'

AProcesses instructions

BSupplies power

CConnects sensors and actuators

DStores data

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing roles of CPU and I/O.

The CPU processes instructions, and the I/O connects sensors and actuators.

5fill in blank

hard

Fill all three blanks to complete the PLC system setup dictionary.

PLC Programming

plc_system = {"CPU": "[1]", "PowerSupply": "[2]", "I/O": "[3]"}

Drag options to blanks, or click blank then click option'

AProcesses instructions

BProvides electrical power

CConnects sensors and actuators

DStores programs

Attempts:

3 left

💡 Hint

Common Mistakes

Confusing storage with power supply or I/O roles.

The CPU processes instructions, the PowerSupply provides power, and the I/O connects sensors and actuators.

Practice

1. Which part of a PLC acts as the brain, processing all instructions?

easy

A. Input module

B. Power supply

C. CPU

D. Output module

Solution

1. Step 1: Understand the role of CPU in PLC

   The CPU processes instructions and controls the PLC operation.

2. Step 2: Compare with other parts

   Power supply provides energy, input modules receive signals, output modules send commands.

3. Final Answer:

   CPU -> Option C

4. Quick Check:

   CPU = Brain of PLC [OK]

Hint: CPU is the brain that thinks and controls [OK]

Common Mistakes:

• Confusing power supply with CPU
• Thinking input module processes data
• Mixing output module with CPU

2. Which of the following is the correct symbol for the power supply in a PLC diagram?

easy

A. A box labeled 'PS' or 'Power Supply'

B. A circle labeled 'I/O'

C. An arrow pointing to output devices

D. A rectangle labeled 'CPU'

Solution

1. Step 1: Identify common PLC diagram symbols

   Power supply is usually shown as a box labeled 'PS' or 'Power Supply'.

2. Step 2: Eliminate other options

   CPU is labeled 'CPU', I/O is not a circle, arrows show signal flow not power supply.

3. Final Answer:

   A box labeled 'PS' or 'Power Supply' -> Option A

4. Quick Check:

   Power supply symbol = Box labeled PS [OK]

Hint: Power supply is labeled 'PS' in diagrams [OK]

Common Mistakes:

• Choosing CPU box as power supply
• Confusing arrows with power supply
• Thinking I/O is power supply symbol

3. Given a PLC with 8 input sensors connected to the input module and 6 output devices connected to the output module, what is the total number of I/O points?

medium

A. 48

B. 8

C. 6

D. 14

Solution

1. Step 1: Understand I/O points

   I/O points are the sum of input points and output points connected to the PLC.

2. Step 2: Calculate total I/O points

   8 inputs + 6 outputs = 14 total I/O points.

3. Final Answer:

   14 -> Option D

4. Quick Check:

   8 + 6 = 14 I/O points [OK]

Hint: Add input and output counts for total I/O [OK]

Common Mistakes:

• Counting only inputs
• Counting only outputs
• Multiplying inputs by outputs

4. A PLC system is not powering on. Which of the following is the most likely hardware issue?

medium

A. Faulty CPU

B. Disconnected power supply

C. Broken output module

D. Input module error

Solution

1. Step 1: Analyze symptoms

   PLC not powering on means no power is reaching the system.

2. Step 2: Identify hardware responsible for power

   The power supply provides energy; if disconnected or faulty, PLC won't start.

3. Final Answer:

   Disconnected power supply -> Option B

4. Quick Check:

   No power = Power supply issue [OK]

Hint: No power means check power supply first [OK]

Common Mistakes:

• Blaming CPU when no power
• Assuming output module stops power
• Ignoring power supply connection

5. You need to expand a PLC system to control 12 new sensors and 10 new actuators. Which hardware components must you add to the existing PLC setup?

hard

A. Add input and output modules

B. Add more CPU units

C. Add extra power supplies only

D. Replace the existing CPU with a bigger one

Solution

1. Step 1: Identify hardware for sensors and actuators

   Sensors connect to input modules; actuators connect to output modules.

2. Step 2: Determine what to add

   To handle more devices, add input modules for sensors and output modules for actuators.

3. Step 3: Consider CPU and power supply

   CPU usually handles more modules without replacement; power supply may need upgrade but not always.

4. Final Answer:

   Add input and output modules -> Option A

5. Quick Check:

   More devices = Add I/O modules [OK]

Hint: Add I/O modules to handle more devices [OK]

Common Mistakes:

• Thinking CPU must be replaced
• Adding only power supplies
• Adding CPU units instead of modules