An Arduino-based Programmable Logic Control (PLC) Lab Activity for Undergraduate Engineering and Technology (ETM) Students

Abstract

A PLC lab activity is developed for use in an Undergraduate Engineering and Technology (ETM) electronics survey class. The existing class uses the Arduino to teach real-time programing and basic electronics. One of the department goals is to include Based Programmable Logic Control (PLC) training in a number of the existing courses including the electronics survey class. To incorporate a PLC programing experience using the Arduino, the freeware software package SoapBox Snap is used. The lab is developed and tested in the classroom. The success of lab activity is evaluated using pre and post surveys, assessments, and classroom observations.

The lab activity objectives are to a) introduce the student to PLC control and ladder logic, b) provide a hands on activity using the PLC, c) prepare the student for future classes in the ETM program, and ultimately employment in industry. PLCs are common in industry and used in other technology classes such as mechatronics, and robotics. Teaching the basics in the electronics course provides familiarity with the concept that potentially improves performance of the students in advanced courses.

The survey course already includes a lab activity using a magnetic starter, and a variable speed motor drive. The magnetic starter lab has two pushbuttons for start and stop, and a dual in-line package (DIP) relay. The relay is used to seal in the starter circuit. An Arduino Pulse Width Modulation (PWM) pin is connected to a transistor amplifier that drives the motor. The motor drive lab is completed first and the PLC lab is completed during the following week. By completing the motor drive lab first wiring is correct before starting the PLC lab. This allows the students to concentrate on the PLC lab.

SoapBox Snap is used to implement the PLC in the Arduino. SoapBox Snap consists of two components, an Arduino sketch, and a PLC programing environment that runs on a windows personal computer (PC). The sketch is uploaded to the Arduino with no changes. The sketch does not contain the PLC program. The program is developed on the PC, including both the ladder logic, and Input / Output (I/O) mapping, then uploaded to the Arduino. The PLC program is stored in the Arduino Electrically Erasable Programmable Read Only Memory (EEPROM).

The lab activity consists of a PLC lecture followed by a pre-quiz/survey. At this point students know what a PLC is, but the question is do they have any understanding. The lab activity consists of two parts. First a magnetic motor starter is implemented. This is followed by a variable speed motor drive. At the conclusion of the lab the quiz/survey is repeated. The post-quiz/survey includes the muddiest question and a few additional questions regarding interest level. Results based on classroom observation, and the quiz/survey results are analyzed. The results are used to determine if the lab should remain as a permanent part of the electronics survey course. The lab provides the students with a hands on PLC experience. The experience gained is useful in the balance of the ETM curriculum. After graduation students can take the experience into their developing careers.