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PLC Programming

⬢ TIER 2Technical
High
Salary impact
2 months
Time to learn
Hard
Difficulty
1
Careers
At a glance

PLCs (Programmable Logic Controllers) are embedded computers running factories: assembly lines, packaging machines, conveyor belts, HVAC systems. Engineers write PLC logic (ladder logic, structured text) to react to sensors (button presses, temp sensors, flow meters) and trigger outputs (motors, solenoids, lights). Mastery takes 6-8 weeks. Only 3% of software engineers know PLC programming; manufacturing and utilities depend on it. Industrial automation engineers earn $100K-$180K; skills command premium because they prevent production downtime ($10K+/hour lost).

What is PLC Programming

A PLC (Programmable Logic Controller) is an industrial computer controlling machinery and processes. It has inputs (sensors, buttons) and outputs (motors, lights, solenoids). You write logic, "if input A and input B, turn on output C", and the PLC runs it thousands of times per second, responding to factory floor conditions. Example: A beverage bottling line has 50 PLCs. Each controls one section: caps at position X, dispenser fills bottle, capping arm tightens. Each PLC reads sensors (bottle present? full?), executes logic, and commands motors (advance conveyor, activate dispenser). If sensor fails, logic stops that section safely, alerts operator.

🔧 TOOLS & ECOSYSTEM
Siemens TIA PortalRockwell LogixProGE FactoryTalkAllen-Bradley PLCMitsubishi GX WorksLadder logicStructured textOscilloscope

💰 Salary by region

RegionJuniorMidSenior
USA$80k$130k$190k
UK£50k£85k£125k
EU€55k€90k€135k
CANADAC$80kC$135kC$200k

🎯 Careers using PLC Programming

Embedded Systems Engineer

❓ FAQ

What's the difference between ladder logic and structured text?
Ladder logic is visual (like circuit diagrams); intuitive for electricians, older. Structured text is text-based (like Pascal/C); easier for complex algorithms. Both compile to same machine code. Choose based on your team: electrician-heavy = ladder. Software engineer-heavy = structured text. Most programs use both.
How do I debug a PLC that's not responding?
Connect with engineering software (TIA Portal, LogixPro). Set breakpoints. Monitor I/O states in real-time. Is the input being read? Is the logic executing? Is the output being set? Step through one rung at a time. Use test mode before deploying to production.
What's the difference between a PLC and an industrial PC?
PLC = small, rugged, deterministic (code runs every 10ms precisely), simple logic, offline programming. Industrial PC = large, runs Windows/Linux, non-deterministic timing, powerful, runs complex software. PLCs control machinery. Industrial PCs run dashboards, data collection, SCADA systems.
How often should I back up PLC code?
Every change. Version control (Git) is best; at minimum, save a backup before each modification. Factory code downtime costs thousands. You need to revert quickly if something breaks.
Can PLCs connect to the internet?
Yes, but risky. Industrial networks were air-gapped for safety. Newer PLCs have Ethernet and OPC UA. If connecting to internet, implement strict firewalls, VPNs, and intrusion detection. Manufacturing vulnerabilities = production stops = huge liability.

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