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EE312 Lab 3

The document provides an introduction and overview of a lab aimed to educate students on programmable logic controllers (PLCs). The lab objectives are to help students identify PLC input/output ports, connect input switches and output loads, program a basic logic ladder diagram to control an LED using three push buttons, and explain ladder diagram programming. Equipment used includes a Windows PC, Omron PLC, and demo boards. The introduction explains how PLCs evolved from electromechanical relays to computer-based controllers used across industries. Key PLC components are input/output units, CPU, programming device, power supply, and memory. Seven ladder logic programs are presented to demonstrate controlling an LED based on different combinations of button presses

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102 views8 pages

EE312 Lab 3

The document provides an introduction and overview of a lab aimed to educate students on programmable logic controllers (PLCs). The lab objectives are to help students identify PLC input/output ports, connect input switches and output loads, program a basic logic ladder diagram to control an LED using three push buttons, and explain ladder diagram programming. Equipment used includes a Windows PC, Omron PLC, and demo boards. The introduction explains how PLCs evolved from electromechanical relays to computer-based controllers used across industries. Key PLC components are input/output units, CPU, programming device, power supply, and memory. Seven ladder logic programs are presented to demonstrate controlling an LED based on different combinations of button presses

Uploaded by

kione
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
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Aim

The lab aims to educate students on being able to:

 Identify the input and the output ports of a PLC.


 Connect input switches and output loads to a PLC.
 Connect a PLC to a PC via serial port.
 Use SYSWIN to write a basic logic ladder diagram program and download it to a PLC.
 Explain the operation of a ladder diagram program.
 Use the address Symbol Editor to add symbol names and comments to PLC ladder programs.
 Use the KEEP, SET and RESET functions in a ladder program.
 Use Timers and Counters in ladder program.

Equipment

 Windows PC with SysWin 3.4 installed


 Omron CPM1/CPM2 PLC
 PLC Demo boards

Introduction

At one time, people were considered the main controlling method for any system. And as years gone by,
control engineering developed control systems which works through electricity. It was the
electromechanical relay that was first employed. It basically is a switch, as it uses switches for power on
and power off. Basic logic control design decisions are carried out by relays, which are the electrical
elements that is used when a low power signal is needed to control the circuit, or when multiple circuits
needs to be controlled by a single signal. As advancements of computers occur, it brought about the
modern revolution, which is the Programmable Logic Controller(PLC). It first came about the 1970’s in
industries of motor manufacturing and automation.

It operates by the use of a programmable memory for its internal storage of instructions for applying
particular functions for instance sequencing, logic, counting, timing and arithmetic of controlling, by
digital or analog input/output parts, different types of machineries or processes. It is composed of both
hardware and software components. PLC checks inputs, generate a decision according to its program,
and uses these decisions to give off outputs which is needed for a process or a machine to function.
Fig 1: Block Diagram of the Basic Parts to a PLC

Programmable Logic Controllers (ijcaonline.org)

It is composed mainly of Input/ Output unit, CPU unit, Programming device, Power supply and memory.
How it works, is that the input source changes the real time electrical analog signals to digital form
which then is given to the PLC through connecting rails. This signal is held in the PLC external image
memory in bits, which are locations. This is carried out by the CPU. The program instructions are
transcribed onto the programming device using mnemonics or symbols and held in user memory. CPU
then fetches those instructions and executes the signal inputs by computing, manipulating, processing
to control the output devices. The outputs are then held in external image memory which controls the
output drives The output signals are monitored by the CPU which keeps updating whatever latest result
stored in the input image memory in line with the alternation in output memory. The CPU also executes
internal programming functions like setting and resetting of the timer, monitoring the user memory.

Knowing the basics of PLCs | EC&M (ecmweb.com)

Introduction of Programming Logic Controller PLC | Working Principles (elprocus.com)

Procedure

 There were three temporary push button Normally Open (NO) switches and a single LED that
was utilized in this lab. The LED was connected to the PLC output 1 0.0 as can be seen below in
Fig 2. The Normal Open switches were connected to the inputs as indicated in previous
programmes.
Fig.2: The Wiring Part to connect LED to the PLC output.

The program was written using SYSWIN in ladder program language in the and for debugging it was
tested without first connecting the switches. The system was first put into MONITOR mode and not in
RUN mode after program was downloaded to PLC. Monitoring which was Online/Monitoring on the PLC
was selected.

The programs from programs 1 to 7 were drawn and downloaded and run in the ladder program
language as can be seen in the following figures as seen below.

Fig 3: Program 1
Fig 4: Program 2

Fig 5: Program 3

Fig 6: Program4
Fig 7: Program 5

Fig 8: Program 6
Fig 9: Program 7
REFERENCE

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