PLC Programming for Electrical Engineers: Complete Beginner to Job-Ready Guide 2026
Industrial automation is one of the most overlooked career paths for electrical engineers. While everyone chases software and IT roles, PLC (Programmable Logic Controller) engineers quietly earn Rs 6 to 22 lakh per annum in India, with demand growing at 18% annually as factories automate. The skill gap is massive. A PLC engineer with 3 years of experience is as sought-after as a software developer with 5 years.
This guide covers everything you need to go from zero PLC knowledge to a job-ready industrial automation engineer.
What is a PLC and Why Should You Care?
A Programmable Logic Controller is a rugged industrial computer designed to control manufacturing equipment, assembly lines, robots, and factory floor processes. Unlike general-purpose computers, PLCs are designed to run 24 hours a day, 7 days a week in harsh environments with temperatures, vibrations, and electrical noise that would destroy a regular computer.
Every factory you have ever seen uses PLCs. Every production line that assembles cars, bottles drinks, packages medicine, or processes chemicals is controlled by PLCs. This is a Rs 50,000 crore industry in India growing rapidly as companies upgrade from manual to automated operations.
PLC Programming Languages (IEC 61131-3 Standard)
PLCs are programmed using five standardized languages defined by IEC 61131-3. Understanding all five makes you versatile across different manufacturers and industries.
| Language | Type | Best For | Difficulty |
|---|---|---|---|
| Ladder Diagram (LD) | Graphical | Relay logic, beginners, electricians | Easy |
| Function Block Diagram (FBD) | Graphical | Process control, analog signals | Easy-Medium |
| Structured Text (ST) | Text-based | Complex algorithms, math, loops | Medium |
| Instruction List (IL) | Text-based | Legacy systems, low-level control | Medium |
| Sequential Function Chart (SFC) | Graphical | Sequential processes, state machines | Medium |
Which language to learn first: Start with Ladder Diagram. It is the most widely used, easiest to debug visually, and expected by 90% of employers when they say “PLC programming”.
Ladder Diagram Basics: Understanding the Fundamentals
Core Ladder Diagram Elements
Normally Open (NO) Contact: Passes current when the associated coil is energized. Symbol looks like two vertical lines with a gap: [ ]
Normally Closed (NC) Contact: Passes current when the associated coil is NOT energized. Symbol has a diagonal line through it.
Output Coil: Energized when the rung has a complete path from left rail to right rail. Controls the actual physical output.
Timers (TON, TOF, RTO): Time-based functions essential for controlling process sequences.
Counters (CTU, CTD, CTUD): Count pulses from sensors, encoders, or manual inputs.
Worked Example: Motor Start-Stop Circuit
Problem: Design a PLC program to start a motor when a START button is pressed, keep it running (latch), and stop when STOP button is pressed or overload trips.
Inputs defined:
- I0.0 = START pushbutton (Normally Open)
- I0.1 = STOP pushbutton (Normally Closed)
- I0.2 = Overload relay contact (Normally Closed)
Outputs defined:
- Q0.0 = Motor contactor coil
Ladder Diagram logic (Rung 1):
The rung contains: [START button (NO)] in parallel with [Motor output contact Q0.0 (NO seal-in)] in series with [STOP button (NC)] in series with [Overload (NC)], driving Output Q0.0.
Explanation: Pressing START completes the circuit and energizes Q0.0 (motor starts). The seal-in contact Q0.0 holds the circuit closed even after START button is released. Pressing STOP or an overload trip opens the NC contacts, de-energizing Q0.0 (motor stops).
This motor start-stop circuit is the single most important PLC program to understand. Nearly every industrial machine uses this as a building block.
Top PLC Brands and Which to Learn First
| Brand | Market Share | Popular Series | Software | Cost (entry kit) |
|---|---|---|---|---|
| Siemens | 35% | S7-300, S7-1200, S7-1500 | TIA Portal | Rs 25,000-80,000 |
| Allen-Bradley (Rockwell) | 28% | MicroLogix, CompactLogix | Studio 5000 | Rs 40,000-1,20,000 |
| Mitsubishi | 15% | FX Series, MELSEC iQ-R | GX Works3 | Rs 15,000-50,000 |
| Delta | 8% | DVP Series, AS Series | ISPSoft | Rs 8,000-25,000 |
| Schneider Electric | 7% | Modicon M221, M241 | EcoStruxure | Rs 12,000-40,000 |
Recommendation for Indian engineering students: Learn Siemens S7-1200 with TIA Portal. Siemens holds the largest market share in India and globally. TIA Portal is the most professional development environment. Siemens LOGO! is a low-cost entry point at Rs 4,000 to 6,000 for a basic unit.
Free PLC Learning Resources and Simulators
You do not need to buy physical PLC hardware to start learning. Several free simulators allow complete programming practice:
- PLCSIM (Siemens): Included free with TIA Portal trial. Simulates S7-300, S7-1200, and S7-1500 PLCs completely in software.
- RSLogix Micro Starter Lite: Free Allen-Bradley simulator for MicroLogix 1000. Good for learning AB programming.
- OpenPLC Runtime: Completely free, open-source PLC runtime. Runs on PC, Raspberry Pi, or Arduino. IEC 61131-3 compliant.
- CODESYS: Free professional PLC development environment used by over 400 PLC manufacturers. Industry-standard for learning.
Recommended starting path: Download CODESYS (free), complete the official getting-started tutorials, practice all five IEC 61131-3 languages. Then choose Siemens TIA Portal or Allen-Bradley Studio 5000 based on your target job market.
PLC + SCADA: Understanding the Full Industrial Automation Stack
PLCs control physical equipment. SCADA (Supervisory Control and Data Acquisition) systems provide the human interface and data logging layer above PLCs. Every serious automation engineer needs both.
Popular SCADA systems in India:
- Wonderware (AVEVA): Market leader in process industries. Heavy usage in oil and gas, chemicals, utilities.
- Ignition (Inductive Automation): Modern web-based SCADA. Growing rapidly. Free trial available.
- WinCC (Siemens): Integrated with TIA Portal. Most common in Siemens installations.
- FactoryTalk (Rockwell): Used wherever Allen-Bradley PLCs are deployed.
12-Month Roadmap: Zero to PLC Engineer
Months 1 to 2 (Foundation): Understand relay logic, electrical symbols, and basic industrial circuits. Study IEC 61131-3 language overview. Install CODESYS. Complete basic Ladder Diagram exercises: start-stop, latching, timer, counter circuits.
Months 3 to 4 (Programming Skills): Learn Timer and Counter functions deeply. Practice motor control sequences. Implement analog input/output handling. Study Structured Text for mathematical operations. Complete 10 practice programs covering common industrial scenarios.
Months 5 to 6 (Real Hardware): Purchase an entry-level PLC kit (Delta DVP at Rs 8,000 to 12,000, or Siemens LOGO! at Rs 4,000 to 6,000). Build physical projects: automatic conveyor control, tank level control with pump automation, traffic light control sequence.
Months 7 to 8 (SCADA): Install Ignition SCADA trial. Connect to your PLC. Build an HMI screen showing your physical project. Learn OPC-UA communication protocol. This combination (PLC + SCADA) separates you from pure electricians in job applications.
Months 9 to 10 (Industry Protocols): Learn Modbus TCP/RTU (most common industrial protocol). Study PROFINET (Siemens) and EtherNet/IP (Allen-Bradley). Implement a multi-device communication project.
Months 11 to 12 (Job Preparation): Document all projects with photos, wiring diagrams, and program printouts. Create a portfolio folder. Apply to automation integrators, manufacturing companies, and OEM equipment builders. Target companies that are setting up new factories, as these hire the most automation engineers.
Salary Expectations for PLC Engineers in India
| Experience | Role | Salary Range (LPA) | Top Employers |
|---|---|---|---|
| Fresher (0-1 yr) | Automation Trainee | Rs 3-6 LPA | System integrators, OEMs |
| 1-3 years | PLC Programmer | Rs 6-12 LPA | Manufacturing companies |
| 3-6 years | Senior Automation Engineer | Rs 12-18 LPA | ABB, Siemens, Rockwell |
| 6-10 years | Automation Lead / Consultant | Rs 18-30 LPA | MNCs, consultancy firms |
| 10+ years | Principal Engineer, Manager | Rs 30-50 LPA | Fortune 500 manufacturers |
Industries Hiring PLC Engineers in India
Automotive: Maruti Suzuki, Tata Motors, Hyundai, Toyota all use thousands of PLCs in their assembly plants. Automation engineers are in permanent demand.
Pharmaceuticals: Every FDA-compliant pharmaceutical plant requires PLC-controlled processes. High salaries, good working conditions.
Food and Beverage: Nestle, ITC, Amul, Parle all operate heavily automated plants.
Steel and Metals: JSW Steel, Tata Steel, SAIL operate large automated rolling mills requiring ongoing PLC expertise.
Oil and Gas: ONGC, Reliance Industries, HPCL use PLCs and SCADA across refineries and pipelines.
Key Takeaways
- PLC engineers earn Rs 6 to 22 LPA with demand growing 18% annually as Indian factories automate rapidly.
- Ladder Diagram is the most important language to learn first, used in 90% of PLC applications worldwide.
- Start with free simulators: CODESYS (free) gives you full professional PLC programming experience without any hardware purchase.
- Siemens S7-1200 with TIA Portal is the recommended starting point for Indian job market relevance.
- Adding SCADA knowledge to PLC skills significantly increases your salary and employability.
- Physical hardware experience matters: Budget Rs 8,000 to 12,000 for an entry-level Delta PLC kit for hands-on practice.
- A 12-month structured roadmap can take a fresh electrical engineer to a well-paying automation role with the right portfolio of projects.
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