The DigiKey Industrial Automation Kit (IA Kit) may be expanded into a trainer for the Crouzet Millenium MXD12SD1ET PLC as shown in Figure 1.
Key Takeaways
- The system is like an industrial breadboard for the Crouzet PLC.
- Keeping the same IA components allows students to see what changes and what does not change when logic is transitioned from relay-based to PLC-based control.
- Figure 2 presents a wiring diagram showing how the system may be configured to integrate sensing, operator controls, PLC logic, and motor control.
- Do not teach troubleshooting as an appendix. Instead, treat it as a persistent technique that grows along with the student’s skills.
- The Crouzet PLC may be used to teach digital logic concepts as described in this article.
This article is part of the DigiKey Field Guide for Industrial Automation
Location: Teach It → Kits
Difficulty: 
Student — difficulty levels explained
Author: Aaron Dahlen | MSEE | Senior Applications Engineer, DigiKey
Last update: 31 Aug 2026
Figure 1: The Crouzet PLC trainer including the DigiKey three-phase motor simulator.
Add These Components to the DigiKey IA Kit
This PLC trainer is an extension of the kit described in this article. The IA Kit provides the base and a variety of components to support the PLC-based exercises. To the IA Kit we add the Crouzet MXD12SD1ET PLC and the DigiKey three-phase motor simulator.
A 24 VDC power supply is also required. The bench style supply featured in Figure 1 is a good match.
Trainer Wiring Diagram
A wiring diagram for the assembled Crouzet PLC trainer is included in Figure 2. This particular layout was selected to make the best use of DigiKey’s IA Kit.
The assembled trainer includes:
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The mom-off-mom selector switch connected to In_1 and In_2 may be used to explore the operation of the set/reset block. For later experiments, it may be used for reset (left) and start (right).
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The green and red pushbuttons provide carryover from earlier relay-based exercises. This helps students transition from the traditional hardwired three-wire control to the PLC equivalent.
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The Weidmüller distribution block serves as the rails the +24 VDC and return supply rails for the industrial breadboard.
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The Crouzet PLC includes a small screen and several pushbuttons. This provides a significant expansion of the operator interface beyond the pushbuttons and dual-colored 22 mm indicator lamp included in the IA Kit.
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The featured Crouzet PLC has solid-state outputs. The interposing relay shown in Figure 2 is used between the PLC and the larger motor starter. The configuration requires students to consider the difference between semiconductor and relay-based PLC outputs. For example, the featured PLC has fast solid-state outputs that may be used to produce a tone over a speaker using the PWM functionality. By contrast, the mechanical interposing relay is slow. However, it can drive a large load and it can provide galvanic isolation if desired.
Tech Tip: The red pushbutton has a normally closed (red) switch contact block. This is an important learning concept as students must be familiar with fail-safe design thinking. Generally, contacts that stop a machine should be normally closed. Breaking the wire results in the same control operation as pressing the button. This should not be confused with an emergency-stop system, which adds a layer of protection above and beyond a traditional PLC. This article introduces the safety PLC and distributed I/O.
Figure 2: Wiring diagram for the Crouzet PLC with an emphasis on motor control.
Recommended Experiments
Previously, I recommended using the Crouzet PLC to teach gate-level digital logic. The IA Kit plus the Millenium PLC provide an incremental progression, with the configuration shown in Figure 1 as a capstone. That article is important as it contains the pedagogical rationale for the Crouzet platform. It explain why Crouzet PLC is not a neutral commodity component decision but is part of a deeper instructional sequence.
As an instructor, I recommend:
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Start Simple: Repeat the lesson on wire nodes as wires are connected to the PLC. This is one of the greatest benefits of the IA Kit. As students wire the kit, they will see the relationships between the PLC and the field devices. The instructor can also inject deliberate wiring errors to reinforce the troubleshooting skills required in a competency-based setting. Stated another way, the troubleshooting mindset is persistent across the course. The complexity follows the students’ abilities as opposed to appending troubleshooting as a final exercise to a “completed” trainer.
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Combinational Logic: Work through the canonical textbook gate-level digital logic exercises. However, add an additional terminology layer focused on signal purpose, as described in this article. Instead of using abstract signal names such as ‘A’ and ‘B’, use functional names such as ‘MotorOVLDLockout’ or ‘PartPresentPermissive’. From the very beginning, students gain experience using the vocabulary and signal semantics of PLC controls.
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Sequential Logic: Traditional logic classes introduce state machines using discrete logic. There is nothing inherently wrong with this approach. However, it consumes considerable time that may not be warranted in an IA curriculum. The Crouzet sequential cam block and SFC solutions are alternatives available within the Crouzet environment. This software scaffolding allows a fast transition from combinational to sequential logic. It also provides several different ways of encoding the state machine. This is especially useful if the semantics from the previous section are introduced with rigor.
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Motor Control from Figure 2": This article would be incomplete without treating Figure 2 as part of the learning process. Implicit in the wiring diagram are lessons on:
- seal-in logic
- interposing relays
- motor start contact welding
- motor starter overloads
- sequencing based on permissives, interlocks, and detected faults
- HMI controls and fault status display
- machine commissioning and the importance of a full functional
- significant troubleshooting as the compact assembly can accommodate many realistic wiring faults
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Modbus TCP: The featured PLC supports Modbus TCP. Toward the end of the semester, students could construct a network with a pair of Crouzet PLCs. They may also explore communication with Modbus sensors and actuators.
Parting Thoughts
There is no single best way to teach PLC.
Fair enough.
Yet, should we teach only the PLC?
In this article, I’ve argued that physically wiring is a critical step to develop troubleshooting skills. I’ve also argued that persistent emphasis on signal semantics is important. Instead of a pure abstraction, we should attach physical and process meaning to the signals.
The PLC is part of a system. Our students need to understand the relationship between the physical wires and signal abstractions.
I’d love to hear your thoughts on this topic. What have I overstated or overlooked?
Sincerely,
APDahlen
About this Author
Aaron Dahlen, LCDR USCG (Ret.), is a Senior Applications Engineer at DigiKey in Thief River Falls. His background in electronics and industrial automation was shaped by a 27-year military career as both technician and engineer, followed by over a decade of teaching.
Dahlen holds an MSEE from Minnesota State University, Mankato. He has taught in an ABET-accredited electrical engineering program, served as coordinator of an electronic engineering technology program, and instructed military technicians in component-level repair.
Today, he has returned to his home in northern Minnesota, completing a decades-long journey that began with a search for capacitors. Read his story here.