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ladder logic

30 articles tagged “ladder logic”.

Flat vector diagram comparing a CTU count-up and CTD count-down PLC counter instruction side by side with accumulated value bars and ladder rung connections
plc countersctu ctdladder logic

CTU vs CTD: PLC Counter Instructions Compared

CTU counts up from zero; CTD counts down from a preset. Learn when to use each, how they differ across platforms, and how to wire both into working ladder logic.

Aug 2, 2026 · 9 min read

Flat vector diagram of three cascading PLC TON timers in ladder logic where each timer done bit triggers the next step in a timed sequence
plc timersladder logicton timer

Cascading PLC Timers: Chain TON Logic Right

Learn how to cascade TON timers in PLC ladder logic to build reliable multi-step timed sequences. Real examples, common mistakes, and field-tested patterns.

Aug 2, 2026 · 7 min read

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 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 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

Flat vector diagram of a tank fill control system showing level sensors, inlet valve, transfer pump, and connections to a PLC I/O rack for a ladder logic exercise
ladder logictank fill controlplc exercise

Tank Fill Control PLC Exercise: Ladder Logic

Build a tank fill control program from scratch. This exercise covers level sensor inputs, inlet valve control, pump sequencing, high-level fault latching, and HMI interlock in ladder logic.

Jul 25, 2026 · 7 min read

Flat vector diagram showing a laptop running a ladder logic simulation with ghost PLC rack and sensor icons connected by dashed lines, representing offline PLC simulation
ladder logicplc simulationcommissioning

How to Simulate Ladder Logic Without a PLC

Learn how to simulate ladder logic in Studio 5000, TIA Portal and CODESYS so you can catch logic errors before commissioning, with real examples and gotchas.

Jul 20, 2026 · 8 min read

Flat vector diagram comparing normally open and normally closed contact symbols in PLC ladder logic rungs
ladder logicplc contactsnormally open vs normally closed

NO vs NC Contacts in PLC Ladder Logic: Full Breakdown

Confused about normally open vs normally closed contacts in PLC ladder logic? Learn what NO and NC mean in hardware vs software, with real wiring examples.

Jul 20, 2026 · 8 min read

Flat vector diagram comparing XIC and XIO ladder logic contact symbols with bit-state labels showing how each instruction evaluates its tag
ladder logicallen-bradleystudio 5000

XIC vs XIO: Ladder Logic Contacts Explained

XIC and XIO are the two most fundamental contacts in Allen-Bradley ladder logic. Learn exactly how each evaluates its bit, where to use them, and the mistakes that catch beginners out.

Jul 19, 2026 · 9 min read

Flat vector infographic comparing TON on-delay, TOF off-delay and TP pulse PLC timer waveforms side by side with labeled input and output signal bars
plc timersladder logiciec 61131-3

TON vs TOF vs TP: PLC Timer Comparison

TON, TOF and TP are the three IEC 61131-3 standard timer types. Learn exactly how each one behaves, where each one fails you, and which to pick for your application.

Jul 19, 2026 · 8 min read

Flat vector diagram of a ladder logic rung showing XIC and XIO contacts connected to an OTE output coil with a TON timer block, representing ladder logic interview questions
ladder logicplc interviewplc programming basics

Ladder Logic Interview Questions: Real Answers

Preparing for a PLC role? These ladder logic interview questions cover contacts, coils, timers, counters, latching, scan cycle, and common gotchas interviewers love to probe.

Jul 16, 2026 · 13 min read

PLC pump station ladder logic exercise diagram showing two pumps, level switches, duty/standby alternation and fault detection
ladder logicplc exercisepump control

PLC Pump Station Exercise: Ladder Logic

Build a realistic two-pump station in ladder logic: level-based start/stop, duty/standby alternation, run-confirm fault detection, and a hand-off-auto selector.

Jul 15, 2026 · 7 min read

Car wash PLC ladder logic exercise diagram showing sensor inputs, state machine, and output devices
ladder logicplc exercisesequencer

Car Wash PLC Exercise: Full Ladder Logic

A step-by-step PLC ladder logic exercise for an automated car wash: inputs, outputs, sequence states, interlocks, and the timing tricks you need to get it right.

Jul 15, 2026 · 6 min read

PLC online monitoring troubleshooting showing live ladder rung status on a laptop connected to a PLC rack
plc troubleshootingonline monitoringladder logic

PLC Troubleshooting with Online Monitoring

Online monitoring turns a running PLC into its own diagnostic tool. Learn the exact steps to isolate faults using live rung status, force tables and tag cross-reference.

Jul 14, 2026 · 8 min read

Keyence KV Studio getting started guide showing PLC rack and ladder logic editor diagram
keyencekv studioladder logic

Keyence KV Studio: A Practical Getting-Started Guide

KV Studio is Keyence's free PLC programming environment for the KV-8000, KV-5500 and KV-7500 series. Here's what you actually need to know to get productive fast.

Jul 8, 2026 · 8 min read

TON TOF TONR PLC timer comparison diagram showing input and output timing waveforms
timersladder logicplc programming

TON, TOF and TONR Timers: What Actually Differs

TON, TOF and TONR timers behave very differently under power loss and input cycling. Here's exactly how each one works, with real ladder examples and common gotchas.

Jul 7, 2026 · 7 min read

CTU CTD and CTUD PLC counter instructions diagram showing preset and accumulated count values
countersladder logicplc programming

PLC Counter Instructions: CTU, CTD and CTUD Explained

CTU, CTD and CTUD counters explained with real preset values, accumulated counts, reset behaviour, and vendor-specific differences you need to know.

Jul 7, 2026 · 9 min read

Five types of PLC programming languages shown as flat vector icons representing IEC 61131-3 standard
plc programming languagesiec 61131-3ladder logic

5 Types of PLC Programming Languages Explained

IEC 61131-3 defines five PLC programming languages. Here is a plain-English breakdown of each, with real examples and honest advice on which to pick.

Jul 4, 2026 · 7 min read

Traffic light PLC exercise ladder logic diagram showing four-phase timer sequencer
ladder logictimerssequencer

Traffic Light PLC Exercise: Full Ladder Logic

A traffic light PLC exercise is the perfect timer and sequencer workout. Build the full four-phase cycle in ladder logic, then add a pedestrian call button.

Jul 3, 2026 · 6 min read

PLC elevator logic exercise diagram showing 3-floor shaft wired to a PLC rack with ladder logic rungs
ladder logicsequencerexercise

PLC Elevator Logic Exercise: Step-by-Step

A complete PLC elevator logic exercise covering floor call latching, direction interlocks, door timers and a state-based sequencer. Real runnable ladder included.

Jul 3, 2026 · 7 min read

PLC bottle filling machine project diagram showing conveyor, fill valve, sensors and PLC rack in flat vector style
ladder logicsequencerhands-on project

PLC Bottle Filling Machine: Step-by-Step Project

A hands-on PLC bottle filling machine project covering I/O design, sequence logic, fill-by-time control, and a real ladder rung you can adapt today.

Jul 3, 2026 · 8 min read

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