Technical Tidbits

This page is dedicated to providing guests to our website with useful automation engineering information and examples.  NEW content will be added to this page once every week or so.

• Topics that will be covered include:
• PLC Programming & IEC61131-3
• SCADA Programming & IEC61499
• HMI with OPC & .NET Technology
• Additional Industrial Engineering Information
• Useful Trivia

If you have a question, comment, or request, please feel free to email us at:  info@isdtech.com.

PLC Programming Example #1

A frequent question arises on how to make one pushbutton both an on and off button.  The ladder diagram below will toggle a "real-world" output between on and off states.

Remember to make the contact for the "real-world" input (the pushbutton) a "pulsed relay".

DEFINITION:  A "Pulse Relay"  -| P |-  goes ON for one program scan only.  The ON and OFF state is not externally output and only operates in the program. 

A "Pulse Relay" only goes on when a rising edge start instruction or a falling edge start instruction is executed.