A practical reference for technicians and engineers building, wiring, programming, and troubleshooting industrial control systems. This index is the navigation hub for industrial automation articles drawn from the DigiKey workbench and field experience. Content is organized by what you are trying to do — not by product category.
Attention Educators: Structured learning pathways are available for selected field-guide content. While the field guide is organized by technical action and uses difficulty icons, the learning pathways arrange selected materials into learner-centric instructional sequences. Not all field-guide content is included in the pathways.
Use the difficulty icons to find your level: 
Student → 
Technician → 
Engineer → 
System Integrator
Last Update: 17 Aug 2026
Latest Additions to the Field Guide
Starter Kit for the Siemens S7-1200 G2 Safety PLC: Parts & Build Guide- Beyond Current Rating: Choosing Between IEC and Definite-Purpose Contactors
- Can a 4-20 mA signal conditioner be series-connected into an existing loop?
- A Reliable Ammeter Connection for 24 VDC Control Circuits
- Quality Standards for Wire-Ferrule Crimps
- Exploring Polarity with DC Industrial Control Relays: A DigiKey Lab
Understand It
The physics, theory, and operating principles behind industrial control systems. No product agenda — just how things work and why. If you want to know what’s happening inside the contactor or why the AS-i bus faulted, start here.
Circuit Protection
Sensors
- Introduction to the Inductive Proximity Sensor
- Radar Tank Level Measurement: Lessons from a 55-Gallon Drum Experiment
- Getting Started with Non-Contact Industrial Thermal Sensors
- Sourcing and Sinking Configurations in Industrial Control Circuits
- Applications of Type PNP and NPN Sensors
- Guide to Precision Encoders: From Quadrature to Hall
- Quadrature Encoder
Relay Logic
Fundamentals
- Teaching Electrical Nodes: Using 3D-Printed Wire Markers to Connect Wiring and Ladder Diagrams
- Recommended Wire Colors for +24 VDC Industrial Control Labs
- Exploring Polarity with DC Industrial Control Relays: A DigiKey Lab
- Relay Normally Open vs Normally Closed Contacts
- AC vs DC Relay Specifications: Coil Ratings, Contact Ratings, and Common Mistakes
- Polarity and Flyback Protection in a 24 VDC Industrial Control Relay
- Relay Jumpers Cut Wiring Time and Panel Clutter
Logic & Control
Timing & Sequencing
Circuit Theory
Motor & Contactor Behavior
PLC Scan Cycle & Memory
Safety Concepts
- What are the attributes of an emergency stop pushbutton?
- What Are Safety Door Interlocks? Wiring Standards and Tamper Protection Explained
- How Are Light Curtains Mounted to Industrial Equipment?
- How Are Light Curtains Aligned?
- Finger vs Hand Light Curtains: Beam Spacing, Safety Distance, and Selection
- Introduction to the Industrial Safety Relay
- Getting Started with the Siemens Safety PLC
Network Fundamentals
24 VDC Control Power
Applied Theory
- A Comprehensive Guide to Magnetic Field Behavior in Relays
- Operation of the Latching Solenoid
- H-Bridge Motor Drive Dynamics: Identification of Current Spikes
- Visualizing Core Saturation and the Voltage-to-Frequency (V/f) Ratio
- Guide to Ratiometric Sensor Applications
- Permanent Magnets as an Energy-Saving Feature of a 3-Phase Motor Starter
- Modeling PLC Digital Inputs: Transitioning from the Microcontroller to the PLC World
Potentiometer Linearization Series
EMI & Power Quality
Teardowns
Industrializing Microcontroller-Based Designs
- Building Blocks of the 4-20 mA Industrial Ecosystem: SPI to Current Loop
- Building Blocks of the 4-20 mA Industrial Ecosystem: Analog Transmitter
- When to Use PCB-Mounted Relay Sockets
- DIY PLC Components: Key Attributes of a 24 VDC Output Driver for Industrial Automation
- The MOSFET Active Clamp: The Case Against a Relay’s Parallel Flyback Diode
Teach It
Structured learning for instructors and students with hardware in hand. Labs, guided Q&A sequences, and curriculum-aligned content. Not theory for its own sake — pedagogy with a workbench.
Kits
Shop Practices
Industry Context
Lab & Trainer Builds
Component Selection for Education
PLC Language for the Classroom
Showcase It
DigiKey demonstrator projects
- DigiKey Industrial Automation Demo: Interactive Sensors
- DigiKey Industrial Automation Demo: IO-Link Ball Float
- DigiKey Industrial Automation Demo: Siemens 3SK1 Safety Relay Demo
Select It
Choosing the right component for the job. Comparisons, selection guides, and specification walkthroughs. The product is the hero here — specific enough to act on.
PLCs
- Are 12 VDC Programmable Logic Controllers (PLC) Available?
- Software Compatibility Between the Arduino Opta and the Schneider Electric Modicon M171/M172 PLCs
- How to Choose the Correct PLC
- Beyond Specs: Soft Requirements for Selecting the Right PLC
- Schneider Modicon M221 Programmable Logic Controller
- Navigating Siemens S7-1200 PLC Model Numbers
Pilot Devices
Relays
- Spring Terminal vs Screw Terminal Connections for Industrial Control Panels
- What is a DIN Rail Relay?
- What Is an Ice Cube Control Relay?
- What Is an Octal Socket?
- Beginner’s Guide to Selecting an Industrial Control Relay
- An Engineer’s Perspective on Power Relays
- Anatomy of a DC Solid-State Relay: Internal Design, Heat Limits, and Wiring Implications
Motor Drives (VFDs)
Panel Hardware
Networks & Comms
Power Supplies
Other
- How to Choose a Fluke Multimeter or Process Calibrator for 4–20 mA Work
- Different Size Pin Diameters in M8 and M12 Circular Connectors
- Locating Siemens SMF Starters and MMS Switches for Fractional HP Motor Control
- An Engineer’s Perspective on Power Transformers
- Wireless Pushbuttons for Industrial Control Panels
- Introduction to the Lighted Pushbutton for Industrial Control Panels
Start It
Platform-specific onramps for when the hardware just arrived. Unbox to first operation. Assumes you chose it already — this is how you get it running.
Integrate It
The convergence of electrical, network, and safety engineering. This category moves beyond physical installation to address systemic automation challenges: distributed I/O, network topology, and safety-rated signaling. We ensure every node is logically mapped, functionally validated, and architecturally secure.
Safety
Panel Construction
Terminal Blocks & Ferrules
I/O Wiring (sourcing/sinking)
Network Cabling (M8/M12)
Program It
Writing, structuring, and organizing control logic. Language-agnostic where possible — the concept is the hero, the platform is the support unless otherwise noted.
PLC
- PLC Ladder Logic FAQs: A Practical Path from Beginner to Mastery
- PLC Latches and the False Dichotomy Between Set/Reset and Traditional Logic
- Guide to Programming a PLC in C++: Cycle Scan
- PLC Programming Language Introduction
Siemens S7-1200 and S7-1500
- Make Your PLC Play a Song: Mastering Siemens PLC Memory Arrays
- Building a State Machine in Function Block Diagram Using Siemens TIA Portal
- Using Ladder Logic Rung with Multiple Serial Connected Coils
- How to Configure the FirstScan Bit in Siemens TIA Portal
- Understanding the Siemens Data Block (DB) File Format in TIA Portal
Siemens LOGO!
Schneider Zelio
Schneider Modicon
- Introduction to the Modicon PLC UDFB
- Introduction to the Schneider Electric TMH2GDB HMI for the Modicon M221 Nano PLC
- Integrating the Banner K50 Pro Optical Series Touch Button with a Schneider Modicon PLC
- How to Configure the Modicon PLC for a Quadrature Encoder
- Single Pushbutton On-Off Control Including a Ladder Logic Demo in the Modicon PLC
Crouzet
- Cell Phone Control of a Crouzet PLC Using Bluetooth
- Prevent Unexpected Equipment Start-Up with Defensive PLC Programming
- Power-On Safety Macro for the Crouzet PLC
- Crouzet Sequential Function Chart Macro for a Three-Phase Motor Starter
- Introduction to Crouzet PLC Sequential Function Chart (SFC) Programming
- PLC Finite State Machine Control Using a Sequence Cam Block
Arduino Opta
Refer to the manufacturer’s information to get started:
- PLC IDE: Getting started with Finder OPTA and PLC IDE - Finder OPTA
- Arduino IDE: Getting Started with Opta™ - Finder OPTA
DigiKey Resources:
- Beginner’s Guide to Connecting Outputs with Arduino Opta PLC
- Beginner’s Guide to Connecting Digital Inputs to the Arduino Opta PLC
- Mapping DigiKey’s Opta PLC Trainer to the Arduino Academy ACE-100 Course
- Arduino Opta PLC Ladder Logic Memory Structures
- Ladder Logic UDFB in the Arduino Opta PLC
- How to View I/O Status on the Arduino Opta
- Programming a PLC in C++: Pointer Injection for Structured Handling of Digital I/O
State Machines
Data Structures (UDT/DB)
PID & Analog
Networks & Protocols
Distributed I/O
Peripherals & Smart Devices
Measure It
- Multimeter Fuse Replacement: Use the OEM-Recommended Fuse, No Substitutions
- Introduction to Megger Insulation Resistance Tester for Motor and Cable Testing
- Understanding Thermal Imaging for Electrical Inspections
- Process Meter First Steps: Source vs. Simulate Mode in a 4-20 mA Loop
Troubleshoot It
Something is wrong and you need to find it. Fault patterns, diagnostic techniques, and real failure modes from the bench. Assumes you know how it should work.
Relays & Contactors
Power Supplies
Safety Systems
Certify It
Compliance, standards, and documentation for panels and systems that need to meet a code. UL, SCCR, and inspection-readiness.
Human Factors
UL 508A
- Peak Let-Through Current FAQs for UL 508A Industrial Control Panel Fuses
- Integrating a 120 VAC Programming Receptacle into a UL 508A Listed Control Panel
- Circuit Breaker Branch Protection vs. Supplementary Protector in a UL 508A Listed Control Panel
- Navigating UL 508A for Industrial Control Panel Enclosures
