Understanding Flow Chart language for PLC's


Thread Starter

Nasir Bashir

I am having some problem in understanding the making of the flow chart. Could you please provide and give me some sugesstions by which i can understand how to make a flow chart.

Nasir Bashir

Jerry Richardson

The flow chart is a graphical diagram of program flow. Whereas Ladder logic is based upon relays which may (once) could act simultaneously, a flowchart is more oriented toward a single processor, which can only do one thing at a time (however fast).

There are several symbols in the diagram, but it seems to me that only two or three are important.

"Start" is a horizontal oval that represents the routine being called or the program being run. It might be a mouse click.

A diamond represents a decision. "Is motor ON?" Generally one line goes in at the top, and at least two leave (at right and bottom). At the simplest, these two paths represent yes or no answers to the question.

A box represents processing. Something the computer can do without making a decision. Flow is generally from the upper left to the lower right, but arrows may be used to show unconventional paths.

Circles may enclose numbers or names to refer to other diagrams or parts of a diagram.

The flowchart may be more abstract, less detailed than a logic diagram, or functional control diagram, but it still represents the logic of the machine.

There are templates (pieces of plastic) to help you draw flowcharts, and you may wish to use graph paper. There are also computer programs. Visio may be a sort of electronic template and paper (though I have not used later versions), but I am sure there are more advanced tools.