Ladder Diagram Design : Petri Net Method

Some systems like manufacture system, telecommunication network & computer, and real-time system nowadays are more complex. All of those system are dynamic and discrete. With the increased system usage, then needs a way to model the system. 

Petri net is a method for modelling a dynamic and discrete system. Petri net could be simulated using computer so it easily to analyse attitude of the system. Petri net provide a form that could be used in process of system planning. Petri net illustrates the system using graphical way so it will easier to understand.

As graphical device, petri net could be used as visual-communication assistance like flowchart, block diagram, state diagram, and networking. 

COMPONENTS

Token is showing an active place.

Transition is showing an event that can happen in the system.

Directed Arc is showing a relationship between "Place" and "Transition".

Place is showing the state of system.

EXAMPLE

START, A+, B+, B-, A-

The merged petri net,