What Is Ladder Logic Programming?

Ladder logic programming is a coding language used to create circuit representations to help people build devices and to give instructions to controllers. While this can be used to build many different circuits, ladder logic programming primarily is used to make programmable logic controllers (PLCs). Aside from building the circuit, this language also enables users to make if/then statements. This language was made to be similar to hardware production systems so common users who knew these systems would not need training, but there still tends to be a learning curve to this programming language.

When a circuit is built, both the people assembling the circuit and the device itself need to know how the circuit works. People need to know so they can create the appropriate hardware, and the device needs to know so it understands how power can flow. With ladder logic programming, the user is able to make a representation for both. The representation built with this language is simple, primarily showing brackets, hyphens and slashes to depict wires, and letters for variables.

The ladder logic programming language has the capability of creating many different circuits, but it primarily has been used to program PLCs. These devices can be programmed with relative ease and are capable of controlling manufacturing and device processes. Aside from their ability to be used for many different purposes, ladder logic coding has many blocks and variables that are especially suited for building PLCs.

Circuits, especially advanced ones, rarely have a simple path. There usually are conditions, such as a portion of the circuit having to remain open for a period of time or only sending power somewhere if a condition has been satisfied. Ladder logic programming addresses this need through if/then statements. This allows the programmer to tell the circuit to perform one operation until a condition appears, and then a new operation will occur from the condition.

Created in the 1970s, ladder logic programming was intended to be simple and to mimic hardware production programs. Targeted users were those familiar with hardware production systems, so those in the industry thought users would not require any training to start building a ladder logic program for a PLC or circuit. While it is similar to this type of work, however, most people do need training to fully grasp ladder logic coding. Training is often slight, however, because this language does tend to be simpler than other programming languages.