18. Program Control Instructions: JSR, MCR, JMP, and Fault Routine


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In PLC programming, not every instruction directly turns on a motor, counts a box, or starts a timer.

Some instructions are used to control how the PLC program executes.

These are called …

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16. PLC Counters: CTU, CTD, and One-Shots


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In industrial automation, PLC counters are used when a machine needs to count events.

A counter can count:

Parts
Boxes
Bottles
Cycles
Machine strokes
Rejects
Pallets
Sensor pulses
Production totals

A counter does not count time.A counter counts how many times …

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12. Seal-In Circuits Explained


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Seal-In Circuits Explained

A seal-in circuit is one of the most important basic patterns in PLC ladder logic and relay logic.

It is commonly used when an operator presses a momentary Start …

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11. Basics of Ladder Logic Programming


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Ladder Logic is one of the most common PLC programming languages used in industrial automation.

It was designed to look similar to electrical relay control circuits, which makes it easier for …

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10. Fundamentals of Logic: AND, OR, NOT in Ladder Logic10.


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Before learning advanced PLC programming, every automation technician must understand the basic logic operations used in ladder logic.

The three most important logic functions are:

AND
OR
NOT

These are the foundation of almost every …

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9. Number Systems for PLC Technicians


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When working with PLCs, it is important to understand that the controller does not “think” the same way humans do.

Humans normally use the decimal system:

0, 1, 2, 3, 4, 5, …

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8. PLC Memory Basics: Bits, Words, DINTs, and Tags


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To understand PLC programming, you need to understand how a PLC stores information.

A PLC does not only turn inputs and outputs ON or OFF. It also stores data in memory.

That …

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5. Troubleshooting When Nothing Works (5 of 13)


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How to Diagnose a Control Panel That Appears Completely Dead

One of the most common troubleshooting situations in an electrical control panel is this:

Nothing works.No lights.No relay response.No motor starter.No PLC …

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9. PLC Troubleshooting: Inputs, Logic, Outputs, and Field Devices (9 of 13)


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How to Diagnose PLC-Controlled Circuits Without Guessing

PLC troubleshooting is one of the most important skills for an automation or maintenance technician. In modern industrial panels, the PLC is often the …

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10. PLC Output LED ON but Device OFF (10 of 13)


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Why the PLC Says “ON” but the Field Device Does Not Energize

One of the most common troubleshooting problems in PLC-controlled panels is this:

The PLC output LED is ON,but the field …

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