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CMR
INSTITUTE OF
TECHNOLOGY
USN
Internal Assesment Test - II Sub: Programmable Logic Conrtroller Code: 15EE 562 Date: 10 /0 9 / 2018 Duration: 90 mins Max Marks: 50 Sem: 5 Branch: EEE Answer Any FIVE FULL Questions Marks
OBE
CO RBT
1 Define PLC. What are the advantages & disadvantages of PLC. [10] CO 1 L 1
2a. Explain the operation of fixed type of PLC with a suitable neat diagram. [ 6 ] CO 1 L 5
2 b. Write a short note on RAM & ROM of a PLC [ 4 ] CO 2 L 1
3 a Write the instruction list for the given ladder diagram [6] CO 2 L 1
3b Write a short note on sourcing and sinking of a PLC [ 4 ] CO 2 L 1
4 Draw the ladder diagram for the given
expression
[ 10 ] CO 2 L 3
5 a 5b 6a 6 b 7a 7b
Differentiate between PLC and PC [ 8 ]
[2]
[4]
[6]
[6]
[4]
CO 1 L 2
Write a short explanation for each of the following analog I/O module
specifications:
a. Channels per module
b. Input current/voltage range(s)
L
Write a ladder diagram to show how a system has to be no output when any
one of four sensors gives an output and otherwise there is to be an output.
CO2 L
Briefly describe the different modes of operation of PLC. CO1^ L
Explain the memory organization of PLC CO2 L
Write a short note on PLC size & PLC application CO 1 L 1
Course Outcomes PO1 PO2 PO3 PO4 PO5 PO6 PO7 PO8 PO9 PO10 PO11 PO12 PSO1 PSO2 PSO CO Discuss history of PLC, its sequence of operation, advantages and disadvantages, main parts and their functions
CO Describe the hardware components of PLC: I/O modules, CPU, memory devices, other support devices, operating modes and PLC programming.
CO Describe field devices Relays, Contactors, Motor Starters, Switches, Sensors, Output Control Devices, Seal-In Circuits, and Latching Relays commonly used with I/O module.
CO Convert relay schematics and narrative descriptions into PLC ladder logic programs Analyze PLC timer and counter ladder logic programs. Describe the operation of different program control instructions
CO Describe the operation of mechanical sequencers, bit and word shift registers, processes and structure of control systems and communication between the processes
CO Discuss the execution of data transfer instructions, data compare instructions and the basic operation of PLC closed-loop control system
Cognitive level KEYWORDS L1 List, define, tell, describe, identify, show, label, collect, examine, tabulate, quote, name, who, when, where, etc. L2 summarize, describe, interpret, contrast, predict, associate, distinguish, estimate, differentiate, discuss, extend L Apply, demonstrate, calculate, complete, illustrate, show, solve, examine, modify, relate, change, classify, experiment, discover. L4 Analyze, separate, order, explain, connect, classify, arrange, divide, compare, select, explain, infer. L Assess, decide, rank, grade, test, measure, recommend, convince, select, judge, explain, discriminate, support, conclude, compare, summarize. PO1 - Engineering knowledge ; PO2 - Problem analysis ; PO3 - Design/development of solutions ; PO4 - Conduct investigations of complex problems ; PO5 - Modern tool usage ; PO6 - The Engineer and society ; PO7- Environment and sustainability ; PO8 – Ethics ; PO9 - Individual and team work ; PO10 - Communication ; PO11 - Project management and finance ; PO12 - Life-long learning
3a. Instruction List start x OR X AND X OUT Y END
3B. Sourcing & Sinking:
Field devices connected to the positive ( 1 ) side of the field power supply are classified as sourcing field
devices.
Field devices connected to the negative ( 2 ) side or DC common of the field power supply are
sinking field devices.
5 b. CHANNELS PER MODULE
- individual circuits on discrete I/O modules are referred to as points,
- circuits on analog I/O modules are often referred to as channels.
- These modules normally have 4, 8, or 16 channels.
- Analog modules may allow for either single-ended or differential connections.
- Single-ended connections use a single ground terminal for all channels or for groups of channels.
- Differential connections use a separate positive and negative terminal for each channel.
- If the module normally allows 16 single-ended connections, it will generally allow only 8 differential connections.
- Single-ended connections are more susceptible to electrical noise.
INPUT CURRENT/VOLTAGE RANGE(S)
- These are the voltage or current signal ranges that an analog input module is designed to accept. The input ranges must be matched accordingly to the varying current or voltage signals generated by the analog sensors. 7b. Memory organization takes into account the way a PLC divides the available memory into different sections. The memory space can be divided into two broad categories: 1. Program files. 2. Data files.
Program Files
Program files are the areas of processor memory where ladder logic programming is stored. They may
include:
- System functions (file 0) —this file is always included and contains various system-related information
and user-programmed information such as processor type, I/O configuration, processor file Name and
password.
- Reserved (file 1) —this file is reserved by the processor and is not accessible to the user.
- Main ladder program (file 2) —this file is always included and contains user-programmed instructions
that define how the controller is to operate.
- Subroutine ladder program (files 3–255) —these files are user-created and are activated according to
subroutine instructions residing in the main ladder program file.
Data Files
The data file portion of the processor’s memory stores input and output status, processor status, the status of
various bits, and numerical data. All this information is accessed via the ladder logic program. These files
are organized by the type of data they contain and may include:
- Output (file 0) —This fi le stores the state of the output terminals for the controller.
- Input (file 1) —This fi le stores the status of the input terminals for the controller.
- Status (file 2) —This fi le stores controller operation information and is useful for troubleshooting
controller and program operation.
- Bit (file 3) —This file is used for internal relay logic storage.
- Timer (file 4) —This file stores the timer accumulated and preset values and status bits.
Counter (file 5) —This file stores the counter accumulated and preset values and status bits.
- Control (file 6) —This file stores the length, pointer position, and status bit for specifi c instructions such
as shift registers and sequencers.
- Integer (file 7) —This file is used to store numerical values or bit information.
- Reserved (file 8) —This file is not accessible to the user.
- Network communications (file 9) —this file is used for network communications if installed or
used like files 10 – 255.
- User-defined (files 10–255) —These files are user defined as bit, timer, counter, control, and/or integer
data storage.
6 b. When the PLC is switched into the program mode, all outputs from the PLC are forced off regardless
of their rung logic status, and the ladder I/O scan sequence is halted.
Run Mode The run mode is used to execute the user program. Input devices are monitored and output
devices are energized accordingly. After all instructions have been entered in a new program or all changes
made to an existing program, the processor is put in the run mode.
Straightforward data exchange with other systems
