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An Introduction to Grafcets

by John Schop

I often find that using SFC's or Grafcets is the easiest way to design industrial automation systems. I have worked for several machine builders, and one of them had given the term 'SFC logic' another meaning. There was absolutely no process in their PLC logic that was not documented by an SFC or as I like to call it, a Grafcet. After some getting used to that, I absolutely loved the way it enabled me to program and troubleshoot complex machinery, and ever since, I've tried to use this method whenever I could.


A Tale of Programming Two PLCs

Developing and managing several different PLCs and HMIs can be a real burden on a PC or laptop.  The problems include:

  • The different software packages can cause conflicts with each other.  Communication problems are a common example
  • Memory gets loaded up with automatically started background services even if you're not using the programs.  This kind of bloat makes everything slower.
  • Some packages don't uninstall well and leave behind a lot of files.
  • Older legacy software may only run on older operating systems.

To remedy the situation there are some options:


Modbus FAQ

General

1. What is MODBUS?

MODBUS is a commonly used industrial communications protocol. It allows the exchange of data between PLCs and computers. It was originally designed for Modicon (Schneider Electric) PLCs but has become widely used by many PLC manufacturers and industrial networks.

2. Why would I use MODBUS?

MODBUS is a common means of gathering data from many different sources for viewing operations, archiving and troubleshooting from a central remote location. It is widely used and a fairly simple protocol. Depending on the application a newer protocol may have more advantage.


Analog Input Simulator (4 Channel, 0-10 Volt, Din Rail Mount)

Analog Input Simulator (4 Channel, 0-10 Volt, Din Rail Mount)

The analog input simulator provides functionality to completely control the inputs of a PLC.

Price: USD $95.00

Digital Input Simulator (8 point, Din Rail Mount)

Digital Input Simulator (8 point, Din Rail Mount)

The digital input simulator provides functionality to completely control the inputs of a PLC.

Price: USD $80.00