PLC Programming is almost all visual. The thought process for designing the PLC program is the same as with other programming languages, but that is where the similarities end. A PLC program is also referred to as ladder logic, or a ladder diagram, due to the resemblance of the program to a ladder. The power rails of the program are on the left and right, with the rungs between them containing the instructions. There are a few options for training on PLCs, with teaching yourself being the most time efficient and flexible.
Determine the type of PLC that will be used for your project. Most companies prefer to use only one brand and type to make their jobs easier.
Obtain a computer and PLC programming software for your PLC to teach yourself as you go. The PLC programming software is specific to the brand of PLC, so verify the make and model before ordering your software.
Start programming with simple tasks. One simple task would be to turn on a light with a switch. When the switch turns on, it will activate an input that will be represented in your program with a normally open (NO) contact that looks like this: --| |--. After that input is activated by the switch turning on, power will flow through the NO contact to a coil that represents the light. The coil will look like this in the program: --( )--. The complete rung will look like this: --| |----( )-- with the vertical power rails on either side.
Once the simple tasks are mastered, then you can start experimenting with more complex functions. Most PLCs can do simple math, with add and subtract blocks in their instruction list. These vary based on brand of PLC, so it is important to look at the documentation provided for more information.
Each rung of a PLC program needs to have an output. It doesn’t necessarily need an input.
Talk to your local PLC vendor. Most of the time, they will offer classes on ladder logic; some classes are also free.
Practice. As with anything, the more you practice, the better you will get.