22-06-2012, 05:11 PM
Design Projects in a Programmable Logic Controller (PLC) Course in Electrical
Engineering Technology
Design Projects in a Programmable Logic Controller.pdf (Size: 134.5 KB / Downloads: 314)
Abstract -
A Programmable Logic Controller (PLC) is a specialized computer used for the control
and operation of manufacturing process and machinery. A junior/senior level PLC course
in a four-year electrical engineering technology institution mainly covers the following
topics: PLC hardware components, developing fundamental PLC wiring diagrams, basics
of PLC programming, timers, counters, program control instructions, data manipulation
instructions, math instructions, sequencer and shift register instructions, PLC installation,
editing and troubleshooting.
Introduction
A programmable Logic Controller (PLC) is a specialized computer used for the control
and operation of manufacturing process and machinery1. It uses a programmable memory
to store instructions and execute functions including on/off control, timing, counting,
sequencing, arithmetic, and data handling2.
Characteristics of Design Projects
Students are required to complete conventional assignments of a regular lecture-based
course including examinations, quizzes, and homework problems. Towards the end of the
semester, students have learned the basic PLC programming instructions. It is a good
time to enhance their practical problem solving abilities by working on a design project
using PLCs. The purpose of the design projects is to motivate creative application of
knowledge, enhance problem-solving skills, and apply real solutions to real needs10.
Examples of Design Projects
Example 1: Monitoring and control of filling a tank
The PLC program simulates a process tank being filled with a fluid. The tank will start
filling (via a valve) whenever the start process button is enabled and the tank is below
50% full. It will shut off when the tank is 100% full. In case the level sensor is out of
calibration or not working properly, there is a high-level safety limit to prevent the tank
from overfilling. If the high limit is met at a preset value of 102% full the process will
shut down and a strobe light will turn on. Indicator lights are activated when the tank
level reaches 50%, 75% and 100% full as shown in the diagram of the tank in Figure 1.
There is a slight dead band to prevent flickering lights when tank levels vary slightly due
to filling or splashing.