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For safety, there is a sensor that detects when a worker is inside the press (S, connected to I:011/ 02), which must be off before the press can be activated. There is also a button that must be pushed 5 times (B, connected to I:011/01) before the press cycle can begin. If at any time the worker enters the press (and S becomes active) the press will be shut down (P and R turned off). Develop the process sequence and sequence bits, and then ladder logic for the states. State all assumptions, and show all work.
1. A machine is being designed to wrap boxes of chocolate. The boxes arrive at the machine on a conveyor belt. The list below shows the process steps in sequence.
1. The box arrives and is detected by an optical sensor (P), after this the conveyor is stopped (C) and the box is clamped in place (H).
2. A wrapping mechanism (W) is turned on for 2 seconds.
3. A sticker cylinder (S) is turned on for 1 second to put consumer labelling on the box.
4. The clamp (H) is turned off and the conveyor (C) is turned on.
5. After the box leaves the system returns to an idle state.

Develop ladder logic programs for the system using the following methods. Don’t forget to

include regular start and stop inputs. i) a timing diagram ii) process sequence bits

plc flowchart -11.1

11. FLOWCHART BASED DESIGN

Topics:

• Describing process control using flowcharts

• Conversion of flowcharts to ladder logic Objectives:

* Baabletodescribeaprocess with aflowchart.
* Be able to convert a flowchart to ladder logic.

11.1 INTRODUCTION

A flowchart is ideal for a process that has sequential process steps.

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