Tag Archives: ladder logic

PLC Learning Series – Program Cyclic Scan


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.

The simplest scan cycle of a PLC consists of 4 steps. Read inputs, execute program, diagnostics, and communication, and update outputs.
We will be looking at each of these steps in a little more detail as we discuss the PLC program cyclic scan. Let’s get started. Keep on Reading!

PLC Learning Series – Understanding Numbers


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 is called binary.

Understanding PLC Numbering Systems
We will be looking at how numbering systems work and some of the common systems that programmable logic controllers use. Let’s get started. Keep on Reading!

EasyPLC – Installing the Software


EasyPLC Software Suite is a complete PLC, HMI, and Machine Simulator Software package. This PLC learning package includes the following:
Easy PLC – PLC Simulation that will allow programming in Ladder, Grafcet, Logic Blocks, or Script.
HMI System – Easily create a visual human-machine interface (HMI)
Machine Simulator – A virtual 3D world with real-time graphics and physical properties. PLC programs can be tested using the EasyPLC or through other interfaces. (Modbus RTU, TCP, etc.)
Machine Simulator Lite – Designed to run on Android Devices.
Machine Simulator VR – Virtual Reality comes to life so you can test, train or practice your PLC programming.
EasyPLC Installing the Software
We will be installing the software and showing you how to order your software package for machine simulation (MS). This includes activating your license. Let’s get started. Keep on Reading!

PLC Learning Series – Memory Backup


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.
PLC Learning Series – Memory Backup
We will now look at the basic understanding of memory in the PLC. Looking at two examples of PLC specifications. We will see how the program is stored and how long data memory will remain when the PLC is not powered up. Let’s get started. Keep on Reading!

PLC Learning Series – What are Outputs?


PLC outputs are the next component of our PLC block diagram. The outputs of the PLC will be controlled by the PLC program. 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 Learning Series - What are Outputs?

PLC troubleshooting outputs will also be discussed. This will be done using a multimeter measuring voltage both at the PLC output and across the discrete output load. We will also measure and control an analog signal output. Let’s get started. Keep on Reading!