Practical Tips and Techniques
Scan of the PLC. Reading inputs, solving logic, setting outputs, communications, etc.
The program control method and instructions will allow us to specify what parts of the logic get solved and when this happens. This will control how the PLC will scan and solve your logic in your program using a synchronous PLC Scan. Understanding the PLC program scan post will explain synchronous and asynchronous program scanning. … Read more
PLC programs scan cyclically. This means that it is repeated many times and in the same order. The primary sequence of a PLC scan is reading the inputs, executing the program, diagnostics, and communication, and updating the outputs. We will look at these scan items with particular attention to how the ladder logic program is … Read more
We can learn plc free by using the Do-More Designer simulator. This is free, fully functional programming and simulator software. The PLC simulator also allows communication through the Ethernet and Serial ports of the computer to help you learn about HMI and communication. This video series will take you through the simulator’s basics of installing, … Read more
Most programmable logic controller (PLC) programs will include a counter instruction. The Productivity 2000 Series PLC has two different counter instructions for your program. These can be used in several different ways to adapt to your application. Basically, counters are used to count up or down to a specific limit. When the limit is reached, … Read more
Logic circuits in a PLC ladder logic program are either on or off. The inputs change, which will affect the outputs. This can be expressed in a timing diagram. The timing diagram or chart will show you how the ladder logic program will respond to the changing states of the inputs and outputs. This visual … Read more
Normally open (NO) contacts or inputs in the PLC ladder logic program do not mean the same as a wired normally open switch. NO contacts on the ladder logic provide the logic condition for the rung to turn on the output. We will be looking at three things about the normally open (NO) contact on … Read more
