Ladder Logic PLC Programming for Beginners

Ladder logic is a popular graphical language for PLC programming that automates industrial machines; it's easy to read, understand, and troubleshoot on live systems, with rails, rungs, and logical expressions.

Explore ladder logic structure, rails and a rung, with input and output instructions, and learn how a PLC scans from top to bottom and left to right.

Master ladder logic terminology, including bool (boolean) and concepts like true/high/on/set and false/low/off/reset, plus normally open and normally closed contacts and their output behavior.

apply truth tables to map boolean logic in ladder logic, using inputs A and B with output X, and learn how all input combinations create the table with 2^n rows.

Learn boolean algebra, using and, or, and not to express logic, with examples X = A B and Y = A or not B, ahead of ladder logic practice.

Explore ladder logic basics by demonstrating a normally open contact: if A, then X, using tags, data blocks, and boolean inputs in a live Portal example.

Learn ladder logic using the normally closed contact to implement not A and produce X when A is false, then compare with the normally open contact.

Apply the and instruction in ladder logic by placing A and B in series to drive output X, making X true only when both A and B are true. Use the factory example to show how the door closed condition and the start button being pressed must both be true for the start signal, illustrated with a truth table and the use of normally open contacts in series.

Explore how the or instruction energizes X when A or B is true, using parallel contacts on a ladder rung and contrasting it with the and instruction.

Learn how to use multiple outputs in ladder logic, understand series and parallel configurations for outputs, and recognize that unlike inputs, outputs energize identically whether wired in series or parallel.

Present the solution to exercise: a three-input and instruction in ladder logic, energizing X when A and B are true and C is false, using truth tables and open/closed contacts.

Learn to implement the three-input OR instruction in ladder logic using A, B, and not C, and examine the truth table to determine when X energizes.

Learn the XOR instruction in ladder logic, where x is true when either A or B is true, but not both. Prepare for a three-input XOR exercise.

Explore how a three-input XOR instruction outputs true for an odd number of true inputs, using four parallel runs with A, B, and C.

Use a latch circuit in ladder logic to start and stop a motor. Pressing start latches output X on; pressing stop clears it, allowing run without holding the button.

Explore ladder logic for basic integer arithmetic, covering addition, subtraction, and multiplication with integer and real data types, and learn to chain results without overwriting outputs.

Explore ladder logic comparator instructions, including greater than, less than, and equal to, and learn how they compare integers or real numbers to energize the correct rung.

Learn to use ladder logic comparators to check if a value lies in a range with inclusive and exclusive endpoints. See two examples using A, B, and C.

Explore the move instruction, which copies a value from one tag to another, such as from tag a to tag x, and see how user input can drive calculations.

Learn how ladder logic uses comparators and math instructions to compute X and Y: if A>B then X=A-B; if A<=B then X=A+B; finally Y=5*X.

Explore the on delay timer in ladder logic, creating time delays such as traffic light cycles, driving outputs after a preset time and understanding timer behavior with inputs.

Operate the off delay timer to set the output true as soon as the input is true, and keep it true for a ten-second delay after the input goes false.

Design a ladder logic oscillator using on delay and off delay timers to drive output y, producing a 5 s on, 5 s off cycle, enabled by input a.

Explore finite state machines as a powerful ladder logic flow-control tool in PLC programming, illustrating state-based outputs and transitions driven by input combinations.

Master finite state machines in ladder logic, using output coils to drive outputs across states, with a state register, comparator, and move instructions for transitions on inputs B and D.

The lecture compares output coil and set/reset instructions in ladder logic, showing how coils energize the output while set and reset latch and clear the state.

Explore a finite state machine built with set/reset instructions instead of output coils, making X true and Y false in state zero, and Y true in state one.

Explore count-up counters (ctu) in ladder logic, counting rising input edges using pv preset value and cv current value, with reset inputs to energize outputs at preset counts.

Learn how one-shot triggers (p trig) produce a high output for a single PLC scan cycle on a 0→1 input change, preventing multiple counts from a button press.

Apply what you learned in ladder logic PLC programming to a traffic light system through exercises six and seven, using a finite state machine and an approach without one.

Explore a traffic light system built with a finite state machine that cycles red, green, and orange, counts green cycles to five, triggers maintenance required, and resets on maintenance performed.

Demonstrates a ladder logic solution for a traffic light system without a finite state machine, using off-delay timers for red, green, and orange, with a maintenance counter and reset.

Learn how to avoid double output writes in ladder logic plc programming, using the help file for instructions, and employing set/reset coils to prevent conflicting tag values.

Celebrate completing the basics of ladder logic programming and joining this learning adventure, and look forward to an upcoming advanced plc course featuring human interface design.