Mapping DigiKey's OPTA PLC Trainer to the Arduino Academy ACE-100 Course

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Key takeaways:

  • DigiKey ’s flexible PLC trainer is fully compatible with Arduino’s ACE-100 foundations course.

  • The DigiKey trainer features the same quality components as found in industrial control panels.

  • I/O mapping of the physical screw-terminals to software tags is an essential skill enhanced by the DigiKey trainer.

  • Wiring and troubleshooting with the DigiKey trainer significantly increases the learning experience.

  • The DigiKey PLC trainer may be expanded to cover additional material such as relay fundamentals.

Introduction

Arduino recently announced the Arduino Opta Essentials Course (ACE-100) offering free hands-on learning for industrial control and automation systems. The material is centered on the Arduino Opta Programmable Logic Controller (PLC). DigiKey’s Opta trainer, as shown in Figure 1, enhances the learning experience with additional lessons in wiring and troubleshooting as described in this DigiKey Lab.

This engineering brief explores the mapping (wire diagram) allowing students to easily perform the ACE-100 lessons on the DigiKey trainer.

Figure 1: Image of the complete PLC trainer showcasing the Arduino Opta PLC and supporting field devices.
Figure 1: Image of the complete PLC trainer showcasing the Arduino Opta PLC and supporting field devices.1920×1652 222 KB

Figure 1: Image of the complete PLC trainer showcasing the Arduino Opta PLC and supporting field devices.

Purchase now: The trainer shown in Figure 1 is available in kit form. Note that the kit does not include the recommended wire ferrules and UL 508A compliant white-with-blue-stripe wire for ground signals.

You may be interested in this page which describes the thought process involved in trainer component selection.

We encourage you to adjust the parts list to meet your student’s needs.

Introduction to the Arduino ACE-100 course

The ACE-100 is the first in a series of Arduino courses focused on industrial controls and automation. It serves as an introduction to the Arduino Opta with guided projects. It begins with a comprehensive introduction to the Opta and the Arduino PLC IDE. Later examples focus on applications such as the bottle filling station as shown in Figure 2. Students will simulate the filling station using the trainer with the various sensors and actuators mapped as shown in Figure 3.

Figure 2: Bottle filling example from the Arduino ACE-100 course.
Figure 2: Bottle filling example from the Arduino ACE-100 course.975×450 92.3 KB

Figure 2: Bottle filling example from the Arduino ACE-100 course.

Figure 3: Mapping of the bottle filling station on to the DigiKey trainer.
Figure 3: Mapping of the bottle filling station on to the DigiKey trainer.988×838 215 KB

Figure 3: Mapping of the bottle filling station on to the DigiKey trainer.

Mapping physical I/O to software

Mapping of physical I/O to descriptive software names (tags) is a fundamental aspect of PLC programming. This abstraction allows the programmer to use English statements when referring to field devices. For example, the tag gxPBStop (global Boolean Push Button Stop) provides a self-documenting descriptor for the normally closed pushbutton attached to the I2 screw terminal. The tag gxPBStop is an abstraction that hides background details, thereby allowing the programmer to focus on the essential actions performed by the stop pushbutton.

These essential mapping operations are performed in the Local I/O Mapping section of the Arduino IDE. The concept is explored in Module 4 of the ACE-100 course under the heading, Understanding Ladder Diagram.

Tech Tip: Use of Hungarian notation is highly recommended for PLC programming in a tag-based environment. With this notation, we prefix each variable with the data type such as “x” for Boolean. We also include the “g” prefix to indicate that a variable is global in scope. As an instructor, I will tell you that this saves a tremendous amount of heartache when your students explore advanced topics. Getting into the habit of explicitly calling out scope (local vs variable vs UDFB) will save hours of troubleshooting. For more information about PLC programming styles, please see this PLCopen Coding Guidelines document.

ACE-100 to DigiKey trainer mapping

The mapping process requires us to walk through several steps:

  1. We identify the field devices (sensors and actuators) for our project. An example, consider the sensor in the bottle filling station from Figure 2.

  2. Map the field devices onto the trainer. This is shown in Figure 3 where a capacitive proximity sensor is used.

  3. Construct your own wire diagram or use an established one to map the field devices to specific I/O. An example from the DigiKey Opta wiring lab is shown in Figure 4. In this example, the proximity sensor is physically attached to the Opta’s I4 input.

  4. Map the screw-terminal I/O to descriptive names following the instructions in the ACE-100 documentation.

Figure 4: Simplified wire diagram for the PLC trainer.
Figure 4: Simplified wire diagram for the PLC trainer.872×633 64.7 KB

Figure 4: Simplified wire diagram for the PLC trainer featured in a DigiKey lab.

Instructor Tip: Don’t let your students get comfortable with a fixed wire trainer. Move things around so they become comfortable with the mapping process. This will serve them well in the field where the need to quickly associate field devices with the software tags.

Parting thoughts

The DigiKey PLC trainer is an adaptable platform that is easily integrates into the Arduino ACE-100 course via this DigiKey Lab. Your students will learn to wire the PLC with representative sensors leading to improved job performance as future technicians or someday, system integrators.

The DigiKey trainer’s flexibility with its high-quality components offers an ideal platform for an introduction to the PLC. Students are certain to use components in their capstone projects. Be sure to keep an inventory.
Let us know what future content you would like to see regarding the Opta or other industrial control topics.

Best wishes,

APDahlen

Related information

Please follow these links to related and useful information:

Questions

The following questions will help reinforce the content of the article.

  1. Define mapping as applied to a PLC’s I/O.

  2. Define the term tag as applied to PLC programming.

  3. What is the purpose of the Local I/O Mapping section in the Opta PLC IDE?

  4. Define Hungarian notation and how it may be used in PLC programming.

  5. Suppose output relay O2 is damaged. To restore the machine’s operation, the technician moves the critical load to O3. Ideally, how many lines of code need to be changed to accommodate this modification?

Critical thinking questions

These critical thinking questions expand the article’s content, allowing you to develop a big picture understanding of the material and its relationship to adjacent topics. They are often open-ended, require research, and are best answered in essay form.

  1. Industrial components are often sold by family. For example, the switch and pushbuttons are Altech Corp. products. As a logistic challenge, determine the DigiKey part number for a selector switch with a mon-off-mon operation.

  2. Search the web for PLC troubleshooting tips. According to your research, approximately what percentage of PLC problems involve wiring to field devices?

  3. What are the benefits and downside of Hungarian notation?

  4. From a pedagogical perspective, what is the advantage of students wiring the PLC?

About this author

Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer, which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this.