Ladder Logic Programming Examples - PLC Practical Problems Example 17 To draw the ladder diagram and mimic the diagram for the automatic metal cutting process. In this process, a metal sheet is allowed to move on the conveyor belt. When the metal sheet is sensed by the sensor, a holder holds the sheet at that instant and Ladder Logic Examples and PLC Programming Examples Traffic Light Ladder Logic Diagram. One of the most used applications for a PLC is the traffic lights. At many schools, universities and even companies you will get the challenge to make a traffic light ladder logic diagram. The traffic light PLC program is a combination of timers to control which lights are turned on and for how long time. Logical vs Physical Data Flow Diagrams Benefits of Logical Data Flow Diagram. A physical data flow diagram shows how the system will be implemented, including the hardware, software, files, and people in the system. It is developed such that the processes described in the logical data flow diagrams are implemented correctly to Logical and Physical Data Flow Diagrams The logical data flow diagram illustrates the processes involved without going into detail about the physical implementation of activities. The physical data flow diagram shows that a bar code—the universal product code (UPC) BAR CODE found on most grocery store items—is used.