FLOW CHARTS IN PROCESS DESCRIPTION FRANK CHINGARANDE

Flowcharting It is a technique often used when planning a program after a written description has been developed. Flowcharting—a method of pictorially representing the operation of a process in a sequential manner. Are used for any field and to illustrate events involving processes of any complexity. Can be used as a Programming Language for example Grafcet &SFC.

Definition A flowchart is a pictorial representation that records, analyses, and communicates information, as well as describes the operational process in a sequential manner. Sequences and relationships that are hard to extract from general descriptions also become obvious when expressed through a flowchart. Even the flowchart symbols themselves have specific meanings, which aid in the interpretation of the solution algorithm.

Features A flow chart is made of STANDARD blocks. Arrows indicate the sequence of the steps. Several smaller flowcharts can be used to further describe the functions specified in the main flowchart The different blocks imply different types of program actions. If the flowchart is not standard, the process is not fully understood.

Every route through a flowchart must lead to an end point and each process step must have one output line. Each decision diamond should have only two outputs which are labelled ‘Yes’ and ‘No’, which means that the questions Flowcharts are frequently used to communicate the components of a system or process Flowchart analysis can also be used for troubleshooting The main flowchart itself should not be long and complex; instead, it should point out the major functions to be performed.

Flowchart Symbols

Example 2 : Tank Filler

A flowchart is shown for a control system for a large water tank. In the flowchart the general flow of execution starts at the top The first operation is to OPEN THE OUTLET VALVE AND CLOSE THE INLET VALVE. 1.START BUTTON PUSHED TANK FILL, FLOW OUT STOP. 2.TANK FULL, OR THE STOP BUTTON IS PUSHED OUTLET OPEN, FLOW STOP 3.WAIT FOR A BUTTON TO BE PUSHED. 4.IS THE START BUTTON PUSHED? YES, INLET VALVE OPEN, OUTLET VALVE CLOSE. 5.WAIT UNTIL THE TANK IS FULL, OR THE STOP BUTTON IS PUSHED. 6.IF EITHER CASE OCCURS THE INLET VALVE IS CLOSED AND THE OUTLET VALVE IS OPENED. 7.THE SYSTEM THEN GOES BACK TO WAIT FOR THE START BUTTON TO BE PUSHED AGAIN. FLOW CHART IS SHOWN BELOW; START

Understanding the process or machine operation is the first step in a systematic approach to solving the control problem. Reviewing strategies for new applications, as well as revising the actual method of control for modifications will help detect errors that were introduced during the planning stages.

Logic Design The logic design can be done through the following 1.Process Description 2.Control Description 3.Define Inputs and Outputs 4.Flow Chart 5.Boolean Equation 6.Ladder Logic

Constructing A Flowchart The general method for constructing flowcharts is: 1. Understand the process. 2. Determine the major actions, these are drawn as blocks. 3. Determine the sequences of operations, these are drawn with arrows.

Importance of flowcharting Is an important first step in improving a process. The flowchart ‘pictures’ assist in acquiring a better understanding of the system or process Gathering this knowledge provides a graphic definition of the system and the scope of the program.

Convenience Suitable for recording complicated processes as opposed to a written description. This is particularly so when programming a long process, and its written description would cover several pages. To overcome this difficulty certain methods of recording have been developed and the most powerful of these are mapping and flowcharting. There are many different types of maps and flowcharts which serve a variety of uses.

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