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PLC Tutorials

Programmable Logic Controllers run machines, production lines and utilities in almost every industry. This series starts with PLC fundamentals and hardware, then moves through programming languages, software tools, project practices, troubleshooting and modern trends such as IIoT-enabled PLCs and cybersecurity.

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1

Getting Started

  1. PLC Introduction What a programmable logic controller is and how it controls a machine: inputs, program and outputs, a worked conveyor example in ladder logic and structured text, the parts of a PLC system, how PLCs differ from relays, PCs, DCS and SCADA, where they are used, key terms and how to start learning.
  2. PLC History and Evolution How the programmable logic controller developed: the relay panels it replaced, the 1968 General Motors specification and the Modicon 084, ladder logic, microprocessor PLCs, networking, IEC 61131-3 and PLCopen, PACs, integrated safety and motion, cybersecurity after Stuxnet, and virtual PLCs, with a timeline and what it means for installed systems.
  3. Importance of PLCs in Industrial Automation Why PLCs dominate machine and process control: deterministic scan, rugged hardware, easy reprogramming, diagnostics and modular I/O, plus real limitations and how PLCs compare with relays, PCs and DCS.
  4. PLC Basic Components The hardware of a PLC system and how to choose it: CPU and memory areas, digital inputs (sinking and sourcing, PNP and NPN), relay and transistor outputs, analog I/O resolution and ranges, special modules, remote I/O, power supply sizing with an example, communication modules, and LED-based troubleshooting.
  5. How PLCs Work How a PLC executes its program: the scan cycle, input and output process images, cyclic, periodic and event tasks (Siemens OBs, Rockwell tasks), asynchronous I/O, scan time and worst-case response time with a worked example, the watchdog, operating modes, retentive memory and scan-related programming mistakes.
  6. Types of PLCs Programmable Logic Controllers (PLCs) come in different types, each designed to cater to specific industrial needs.
  7. PLC Vendors Compared A vendor-neutral guide to PLC platforms: controller families, engineering software, native networks, safety and motion options and typical fit for Siemens, Rockwell Automation, Mitsubishi Electric, Schneider Electric, Omron, Beckhoff, B&R, CODESYS-based and open Linux controllers, plus virtual PLCs, lifecycle notices and selection criteria.
2

Programming

  1. PLC Programming Languages The IEC 61131-3 PLC programming languages explained with the same tank-filling example written in ladder diagram, function block diagram, structured text, sequential function chart and instruction list; program organisation units, data types, timers, counters and edge detection, vendor names for each language, and how to choose.
  2. PLC Programming Software and Tools How PLC engineering software is used in practice: what a project contains, hardware configuration, offline and online work, simulation and virtual commissioning, software and firmware version compatibility, licences, comparing and version control of PLC programs, automation interfaces and PLCopen XML, with the main tools per vendor.
  3. PLC Programming Best Practices A practical PLC coding standard: program structure by equipment, naming conventions, reusable function blocks with a motor block example, state machines for sequences, interlocks and permissives, alarms and diagnostics, analog handling, fail-safe behaviour, comments, common mistakes and a code review checklist.
  4. Servo Motion Control How servo motion control works: cascaded position, velocity and current loops, servo motors and encoders, motion networks, sizing (torque, speed, inertia ratio), tuning, PLCopen motion function blocks, homing, electronic gearing and cams, drive safety functions and troubleshooting.
3

Applications

  1. Manufacturing and Production Lines How PLCs control discrete manufacturing: typical machine applications (conveyors, packaging, assembly, robot cells, presses, palletisers), what the PLC does in each, line control and machine-to-machine signals, PackML states, a production line architecture, safety integration, and collecting OEE and traceability data for MES.
  2. Process Control How PLCs are used in continuous and batch process control: pump stations, chemical dosing, level, flow, pressure and temperature loops, PID in PLCs, sequences and batch, process skids and utilities, process object libraries, redundancy, integration with SCADA and DCS, and when a DCS is the better choice.
  3. Building Automation How building automation systems work: BMS architecture, DDC controllers vs PLCs, BACnet, Modbus, KNX and DALI, HVAC and chiller plant control, lighting, energy metering, interfaces to fire and security systems, and when SCADA is used.
  4. Energy Management How to implement energy management in PLCs: reading power meters, calculating energy KPIs, peak demand control and load shedding, VFD speed control, compressor and pump sequencing, and idle-mode logic.
  5. Transportation Systems Where PLCs are used in transportation infrastructure and where they are not: airport baggage handling, road tunnel ventilation and safety, rail wayside and depot systems, port cranes and conveyors, parking and traffic, with typical architectures.
4

Troubleshooting & Challenges

  1. PLC Troubleshooting Guide A practical PLC troubleshooting method: status LEDs, diagnostic buffers, I/O and field wiring checks, communication faults, program and scan-time problems, plus a preventive maintenance checklist.
  2. Upgrading and Integration Challenges How to plan a PLC migration or upgrade: auditing the installed base, compatibility issues, migration strategies, code conversion, testing, cutover, rollback and a practical checklist.
  3. Security Concerns Why PLCs are vulnerable, what real ICS incidents teach (Stuxnet, Ukraine grid attacks, TRITON, PIPEDREAM, exposed PLCs), and a practical defence-in-depth checklist for controllers, networks, remote access and recovery.
5

Projects & Standards

  1. PLC Standards (IEC 61131, Machine Safety) The standards that apply to PLC projects, organised by task: IEC 61131 and IEC 61499 for controllers and programming, PLCopen, machine safety (ISO 12100, ISO 13849-1, IEC 62061, IEC 60204-1, NFPA 79), process safety (IEC 61508, IEC 61511), panels (UL 508A), networks, EMC, cybersecurity (IEC 62443), ISA-88 and ISA-95, and EU machinery rules.
  2. PLC Project Process How to run a PLC automation project for a machine, line or skid: requirements, functional specification, risk assessment and machine safety, I/O list and hardware design, programming, simulation, FAT, installation, SAT and commissioning, handover and lifecycle support, with key documents, best practices for each phase and common pitfalls.
  3. Case Studies and Successful Implementations Five worked PLC application examples: conveyor with jam detection, duty/standby pump station, tank level control, batch mixing sequence and a bottle reject station, each with I/O list, control narrative, interlocks and commissioning checks.
7

References

  1. References and Further Reading A curated, verified list of PLC learning resources: textbooks for beginners and professionals, IEC 61131-3 references, standards bodies, protocol organisations, free vendor software and ways to practise.