How Ladder Logic Program Scan Works

How Ladder Logic Program Scan Works

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

Timing Diagram NOT Just Used for a Timer

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

Create a PLC HMI Training Learning Environment

We will now create a PLC with HMI Training and learning environment. All of the software is free and fully functional. Learn PLC programming and use a powerful HMI (Human Machine Interface) easily and free. We will use the Automation Direct Do-More programming software tied into the Advanced HMI learning package via Modbus TCP. Setting … Read more

How to Implement Modbus TCP Protocol VBA Excel

We will use Visual Basic for Applications (VBA) to communicate to a PLC using Modbus TCP protocol. Reading ten registers in the PLC and displaying a bar graph in Excel. Previously we have used VB6 to communicate Modbus TCP. Sequence for Modbus TCP on Excel using VBA The following steps will be done: Explain Modbus … Read more

Omron Host Link Protocol Part 2 – VBA Excel

We will not use VBA in Excel to communicate to an Omron PLC. This will use the serial host link protocol. ACC Omron Host Link VBA In Part 1, we used VB6 to communicate from the computer to the PLC (Host Link Protocol). We will now use Visual Basic for Applications (VBA) to accomplish the … Read more

Three Free PLC Programming Software Tools

Three Free PLC Programming Software Tools

Every manufacturer has there own software to program the programmable logic controller (PLC) or the human-machine interface (HMI). However, there are a few tools that are free which will help in the development of your PLC programs. We will look at three of these software tools and show how beneficial they can be to you. … Read more