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PLC and Automation Guides, Page 2

In-depth PLC programming and industrial-automation guides: ladder logic, timers, SCADA, HMI and communication, plus the practical know-how the field runs on.

Side-by-side timing diagram comparing a retentive PLC timer that holds its accumulated value versus a non-retentive timer that resets to zero when the enable signal drops
plc timersretentive timerladder logic

Retentive vs Non-Retentive PLC Timers: Key Differences

Retentive and non-retentive PLC timers behave completely differently when the enable bit drops. Learn which to use, how each resets, and see real ladder examples across platforms.

Aug 2, 2026 · 8 min read

Flat vector diagram of three PLC timer ladder rungs labeled TON, TOF and TP each with a timing waveform showing input and output signal behavior
plc timersladder logicton tof tp

PLC Timer Ladder Logic: 5 Practical Examples

Five practical PLC timer ladder logic examples covering TON, TOF and TP instructions, with timing diagrams, gotchas and field-tested advice for Rockwell and generic platforms.

Aug 1, 2026 · 8 min read

Flat vector timing diagram comparing a TON timer that resets on false rung with a retentive TONR timer that holds its accumulated value across multiple enable pulses
retentive timerplc timersladder logic

Retentive Timer in PLC Ladder Logic Explained

A retentive timer keeps its accumulated value when power is lost or the rung goes false. Learn how TONR works, when to use it, and see real ladder examples.

Aug 1, 2026 · 9 min read

Flat vector ladder logic diagram showing a set-reset flip-flop with OTL and OTU latch coils driving a shared output tag on a PLC rack
ladder logicset reset flip flopplc programming

Set-Reset Flip-Flop in Ladder Logic: Full Guide

Learn how the set-reset flip-flop works in PLC ladder logic, how it differs from a seal-in rung, and when each pattern belongs in your program.

Aug 1, 2026 · 8 min read

Flat vector diagram showing a PLC input signal falling edge triggering a single OSF one-shot output pulse in ladder logic
one-shotedge detectionladder logic

Falling-Edge One-Shot in Ladder Logic: OSF Explained

The OSF instruction fires a single scan pulse on a signal's falling edge. Learn exactly how it differs from OSR, where it saves you from logic bugs, and see a real worked example.

Jul 31, 2026 · 8 min read

PLC ladder logic rung showing an OSR one-shot rising instruction converting a sustained input signal into a single-scan output pulse
ladder logicone-shotedge detection

One-Shot Rising Edge in Ladder Logic: OSR Explained

Learn how the OSR (one-shot rising) instruction works in PLC ladder logic, when to use it, and how to avoid the single-scan pitfall that catches every newcomer.

Jul 31, 2026 · 8 min read

Flat vector infographic showing four ladder logic interlock rung patterns for PLC programming, including permissive, mutual exclusion, run confirm and safety guard circuits
ladder logicinterlocksplc programming

Ladder Logic Interlocks: How They Work and Why

Ladder logic interlocks stop dangerous or invalid machine states before they happen. Learn the four core interlock patterns, see real rung examples, and avoid the wiring gotchas that bite engineers on commissioning day.

Jul 31, 2026 · 8 min read

Flat vector ladder logic diagram showing OTL latch coil and OTU unlatch coil rungs with a shared retentive bit and memory icon
ladder logiclatching coilplc programming

OTL and OTU Latch Coils in Ladder Logic Explained

OTL and OTU latch coils hold state through a power cycle. Learn how they work in ladder logic, how they differ from seal-in rungs, and when each belongs in your program.

Jul 30, 2026 · 8 min read

Flat vector diagram of a PLC rack showing input module connected to field sensors and output module connected to actuators with signal path arrows through optocouplers
plc i/o modulesplc inputsplc outputs

How PLC Input and Output Modules Work

PLC input and output modules are more than just terminal strips. Learn exactly how signals get conditioned, isolated, and mapped into CPU memory on every scan.

Jul 30, 2026 · 9 min read

Flat vector diagram comparing PLC direct addressing, indirect addressing with an array index pointer, and symbolic tag addressing across three memory layout panels
plc addressingladder logicplc programming basics

PLC Addressing Modes: Direct, Indirect and Symbolic

Direct, indirect and symbolic addressing each work differently inside a PLC. This guide breaks down how each mode works, when to use it, and the gotchas that catch engineers off guard.

Jul 30, 2026 · 9 min read

Flat vector infographic of the PLC scan cycle showing four phases arranged in a circle: input scan, program execution, output scan, and housekeeping with connecting arrows
plc scan cycleplc basicsladder logic

How the PLC Scan Cycle Works: Step by Step

The PLC scan cycle is the heartbeat of every control system. Learn exactly what happens during input scan, program execution, and output scan, with real numbers and field gotchas.

Jul 29, 2026 · 10 min read

Flat vector diagram of a PLC rack with internal bit memory cells highlighted in teal and grey showing how internal flags connect input and output logic rungs
internal bitsplc flagsladder logic

PLC Internal Bits: Flags, Coils and How to Use Them

Internal bits, flags and internal coils let your PLC logic communicate with itself across rungs. Learn what they are, how to use them correctly, and the gotchas that trap beginners.

Jul 29, 2026 · 9 min read

Flat vector diagram of a PLC controller rack showing CPU, I/O modules, power supply, and connections to sensors and actuators representing a complete PLC system
plc basicsplc programmingwhat is a plc

What Is a PLC Controller and How Does It Work?

Learn what a PLC controller is, how it executes logic in a repeating scan cycle, and how inputs, outputs, and memory work together to control real machines.

Jul 29, 2026 · 8 min read

Flat vector diagram of an EtherNet/IP network with a PLC rack, managed switch and three remote adapter nodes, one node highlighted in amber showing a communication loss fault
ethernet/ipcommunication faultsplc troubleshooting

EtherNet/IP Communication Loss: How to Diagnose It

EtherNet/IP communication loss can halt a whole production line in seconds. This guide walks through every layer of the fault, from cable to CIP timeout settings, with real diagnostic steps.

Jul 28, 2026 · 10 min read

Flat vector diagram of a PLC analog output module wiring to a VFD with a multimeter measuring the 4-20 mA current loop and fault indicators at key points
analog output fault4-20ma troubleshootingplc fault diagnosis

PLC Analog Output Faults: How to Diagnose Them

Analog output faults are sneaky: the PLC logic looks fine but nothing moves. Learn how to isolate 4-20 mA and 0-10 V AO faults in under 20 minutes.

Jul 28, 2026 · 9 min read

Flat vector diagram showing a six-step PLC fault finding flowchart with icons for a PLC rack, multimeter, laptop, sensor, terminal block and a green checkmark
plc fault findingplc troubleshootingfault diagnosis

PLC Fault Finding: A Systematic 6-Step Method

Learn a systematic 6-step PLC fault finding method: gather clues, isolate the fault layer, use online monitoring, test I/O, and verify the fix. Real field examples included.

Jul 28, 2026 · 7 min read

Flat vector diagram of a PLC digital input module with sensor wiring and a multimeter measuring input voltage at a terminal block
plc input faultdigital input diagnosisplc troubleshooting

PLC Digital Input Faults: How to Diagnose Them

PLC digital input faults are deceptive. The status bit looks fine but the machine misbehaves. Here is how to systematically find the real cause in minutes.

Jul 27, 2026 · 9 min read

Flat vector diagram showing PLC communication faults with broken network connections between a PLC rack, HMI, remote I/O module and VFD drive
communication faultsindustrial networking

PLC Communication Faults: How to Diagnose Them

PLC communication faults kill production fast. This guide walks you through diagnosing lost connections between PLCs, HMIs, remote I/O and drives with real steps and field-tested methods.

Jul 27, 2026 · 9 min read

Flat vector diagram of a Mitsubishi MELSEC PLC rack with GX Works3 error log window showing Mitsubishi PLC error codes on a connected laptop
mitsubishi plcplc error codesmelsec troubleshooting

Mitsubishi PLC Error Codes: How to Read and Fix Them

Mitsubishi MELSEC PLCs log specific error codes when something goes wrong. This guide explains how to read them in GX Works3, what the most common codes mean, and how to fix each one.

Jul 27, 2026 · 9 min read

Flat vector diagram of a PLC rack showing a power supply module, CPU and I/O modules with a multimeter probing the 24 VDC supply rail, illustrating PLC power supply fault diagnosis
plc troubleshootingpower supply faultsplc maintenance

PLC Power Supply Faults: How to Diagnose Them

PLC power supply faults are among the most misdiagnosed problems in industrial automation. Learn exactly how to test, isolate and fix them with a multimeter and a clear method.

Jul 26, 2026 · 10 min read

Flat vector diagram of an Omron NX PLC rack connected to a laptop running Sysmac Studio with an error code event log displayed on screen
omron plc error codesplc troubleshootingsysmac studio

Omron PLC Error Codes: How to Read and Fix Them

Omron PLC error codes explained: what each severity level means, where to find the details in Sysmac Studio and CX-Programmer, and how to clear them safely.

Jul 26, 2026 · 8 min read

Flat vector diagram of PLC output module channels connected to relay, transistor and analog loads with diagnostic measurement badges on each circuit
plc output faultplc diagnosticsoutput troubleshooting

PLC Output Faults: How to Diagnose Them Fast

PLC output faults stop machines cold. Learn how to diagnose relay, transistor and analog output failures fast using the right tools and a proven sequence.

Jul 26, 2026 · 9 min read

Flat vector diagram of a Siemens S7-1200 PLC connected to a laptop displaying a diagnostic buffer with amber error code badges and teal module icons
siemens plc error codestia portal diagnostics

Siemens PLC Error Codes: How to Read and Fix Them

Siemens PLC error codes tell you exactly what went wrong if you know where to look. This guide covers diagnostic buffers, OBs, and fixes for the most common faults.

Jul 25, 2026 · 8 min read

Flat vector diagram showing a three-motor start sequence connected to a PLC output rack with timed interlock arrows and fault latch symbols
motor sequenceladder logicplc exercise

3-Motor Start Sequence PLC Exercise: Ladder Logic

Learn how to write a 3-motor timed start sequence in PLC ladder logic. Full rungs, tag names, fault handling and a worked Rockwell example included.

Jul 25, 2026 · 8 min read