PLC POCKET · ACADEMY

PLC Academy

Field-tested PLC lessons for automation engineers. Read each preview free; unlock the full lessons and live tools in the app.

Basics

What is a PLC? Programmable logic controllerWhat a PLC is, how it works and how it differs from relay panels — a clear starting point for automation engineers.What is the PLC scan cycle?A PLC reads inputs, runs the program and writes outputs — why this cycle matters and how it drives edge detection.

Signal & Analog

Why is the 4-20 mA current loop used?What the 4-20 mA signal is, what live zero means and why it resists noise — plus the analog scaling logic.

Ladder Logic

Start/Stop seal-in (latch) circuitThe most basic ladder circuit: start, seal-in, stop. Why must the e-stop be NC?

Timers & Counters

PLC timers: TON vs TOF vs TPThe difference between on-delay, off-delay and pulse timers — with examples.

Communication

What is Modbus? Master, slave and function codesHow Modbus TCP/RTU works, register tables and the most common function codes FC01-FC06.

Wiring

Sink vs source: PNP/NPN sensor wiringPNP vs NPN sensors, where to wire the PLC input common, and brand terminal names.

Troubleshooting

PLC troubleshooting: a systematic approachHow to find a fault fast by following the signal chain instead of swapping parts at random.

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