Practical Tips and Techniques
A human-machine interface (HMI) is present in some form for every PLC. The HMI connects a user to a machine system to exchange information or control data. This interaction with the system can be through hardware or software. HMIs offer different people information and control in many ways for the automated system. Operators, supervisors, mechanics, … Read more
Developing a programmable logic controller (PLC) program can be broken down into five steps. These programming steps are as follows: Five Steps to PLC Program Development Step 1 – Define the task Step 2 – Define the Inputs and Outputs Step 3 – Develop a logical sequence of operation Step 4 – Develop the PLC … Read more
Programmable logic controllers (PLC) use a cyclic scan. The time that it takes to complete one scan is called Scan Time. Typical scan times range from 10 milliseconds to 10 microseconds. This translates from 0.01 to 0.0001 seconds per PLC scan. Understanding how the program scan will help us in programming and troubleshooting the PLC. … Read more
All programmable logic controllers (PLC) have the same numbering system at their core. This is the same with all computers as well. The status of any memory location can be either on or off. A one (1) will represent an on or “True” status and zero (0) will represent an off or “False” status. This … Read more
PLC memory is very similar to personal computer memory. There is the operating system and firmware of the processor and connected modules. PLC programs and data that are used by the program are also stored in the memory. We will now look at the basic understanding of memory in the PLC. Looking at two examples … Read more
PLC outputs are the next component of our PLC block diagram. The PLC program will control the outputs of the PLC. Controlling outputs is one way to get the inputs to change. We will be looking at digital and analog outputs that can be wired to the programmable logic controller. PLC troubleshooting outputs will also … Read more