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Industrial Automation, PLC, VFD, and Troubleshooting

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34. How to Read and Understand an Existing PLC Program ( 34 of 35 )


August 15, 2026 JoeGuardian 0

Opening an unfamiliar PLC program can feel overwhelming.

You may see:

Dozens of routines

Hundreds or thousands of tags

Timers and counters everywhere

Interlocks

Permissives

Fault logic

HMI commands

VFD control

Analog signals

Communication logic

Old logic that nobody remembers

Comments that may …

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35. PLC Commissioning Checklist ( 35 of 35 )


August 15, 2026 JoeGuardian 0

Commissioning is the stage where a PLC control system moves from programmed to proven in the real machine.

A program may look correct offline and still fail during startup because commissioning …

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Bonus — PLC Input and Output Buffering: Building Cleaner and Safer Logic


August 15, 2026 JoeGuardian 0

Throughout this PLC series, we repeatedly used an important programming concept:

Do not build your entire machine logic directly from physical I/O addresses.

Instead, create a clean separation between the real hardware …

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0. Industrial Sensors Explained: The Foundation of PLC Feedback (0 of 15)


May 25, 2026 JoeGuardian 0

Introduction

In industrial automation, the PLC does not physically “see” the machine, conveyor, door, bottle, box, valve, or actuator. The PLC depends on sensors to know what is happening in the …

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1. What Is an Industrial Sensor? Contact vs Non-Contact (1 of 15)


May 25, 2026 JoeGuardian 0

Introduction

In industrial automation, sensors are one of the most important parts of a control system. A PLC can execute logic, energize outputs, control motors, start conveyors, open valves, and trigger …

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2. Discrete vs Analog Sensors Explained for PLC Technicians (2 of 15)


May 25, 2026 JoeGuardian 0

Introduction

In industrial automation, sensors provide the feedback that allows a PLC to understand what is happening in the real machine. However, not all sensors send the same type of signal.

Some …

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3. How to Select the Right Sensor for an Industrial Application (3 of 15)


May 25, 2026 JoeGuardian 0

Introduction

Selecting the right sensor is not just about choosing a device that can detect something.

In industrial automation, the correct sensor must detect the right condition, at the right time, in …

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10. Ultrasonic Sensors: Distance and Level Detection (10 of 15)


May 25, 2026 JoeGuardian 0

Introduction

Ultrasonic sensors are industrial sensors used to detect distance, presence, or level by using sound waves.

Unlike photoelectric sensors, ultrasonic sensors do not depend on light reflection. This makes them useful …

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12. Encoders: Incremental vs Absolute Position Feedback (12 of 15)


May 25, 2026 JoeGuardian 0

Introduction

In industrial automation, not every feedback signal is a simple ON/OFF input.

Sometimes the PLC or controller needs to know:

How fast is the shaft moving?How far did the conveyor travel?What position …

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15. Using Sensor Feedback in PLC Logic: Permissives, Interlocks, Faults, and Alarms (15 of 15)


May 25, 2026 JoeGuardian 0

Introduction

Industrial sensors are not installed only to turn a PLC input ON or OFF.

They are installed to give the PLC useful feedback from the real machine.

A sensor can tell the …

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  • Analog Signals
  • Automation Technician Roadmap (1 of 41)
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  • HMI \ SCADA Fundamentals
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  • Industrial Sensors (1 of 15)
  • Industrial Troubleshooting (1 of 13)
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  • Variable Frequency Drives (1 of 19)