27.4 DESIGN CASES

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27.4.1 PLC Interface To a Robot

Problem: A robot will be loading parts into a box until the box reaches a prescribed weight. A PLC will feed parts into a pickup fixture when it is empty. The PLC will tell the robot when to pick up a part and load it into the box by passing it an ASCII string, "pickup".

Figure 418 Box Loading System

Solution: The following ladder logic will implement part of the control system for the system in Figure 418.

Figure 419 A Box Loading System