1.2 FLOW CHARTS
• Good when the PLC only does one thing at a time in a predictable sequence.
• Basically, we can follow a flowchart one step at a time. Connecting lines indicate the sequences, and the shapes indicate the action/function.
• The real advantage is in modeling the process in an orderly manner.
• General rules for putting these together are,
- determine what the major actions are, these become the boxes.
- determine what sequence the actions normally follow, this determines the lines between elements.
- determine where the sequence may change, these become the decision diamonds.
• The flowchart from the previous example can be converted to ladder logic. The first step is to name each state. From there the states can be converted to ladder logic using MCR blocks.
• For practice,