Presentation on theme: "FLOWCHART BASED DESIGN A flowchart is ideal for a process that has sequential process steps. The steps will be executed in a simple order that may change."— Presentation transcript:
FLOWCHART BASED DESIGN A flowchart is ideal for a process that has sequential process steps. The steps will be executed in a simple order that may change as the result of some simple decisions
The symbols used for flowcharts are
SUMMARY Flowcharts are suited to processes with a single flow of execution. Flowcharts are suited to processes with clear sequences of operation.
STATE BASED DESIGN A system state is a mode of operation. A State based system can be described with system states, and the transitions between those states
A state diagram
The most essential part of creating state diagrams is identifying states. 1. Consider the system, What does the system do normally? Does the system behavior change? Can something change how the system behaves? Is there a sequence to actions? 2. List modes of operation where the system is doing one identifiable activity that will start and stop. Keep in mind that some activities may just be to wait.
SUMMARY State diagrams are suited to processes with a single flow of execution. State diagrams are suited to problems that has clearly defines modes of execution. Controller diagrams can be converted to ladder logic using MCR blocks The sequence of operations is important when converting state diagrams to ladder logic.
TIMING DIAGRAMS Timing diagrams can be valuable when designing ladder logic for processes that are only dependant on time. The timing diagram is drawn with clear start and stop times. Ladder logic is constructed with timers that are used to turn outputs on and off at appropriate times
The basic method is 1. Understand the process. 2. Identify the outputs that are time dependant. 3. Draw a timing diagram for the outputs. 4. Assign a timer for each time when an output turns on or off. 5. Write the ladder logic to examine the timer values and turn outputs on or off.
Timing Diagram Door opener has a button that will open two doors. When the button is pushed (momentarily) the first door will start to open immediately, the second door will start to open 2 seconds later. The first door power will stay open for a total of 10 seconds, and the second door power will stay on for 14 seconds.
SUMMARY Timing diagrams can show how a system changes over time. Process sequence bits can be used to design a process that changes over time. Timing diagrams can be used for systems with a time driven performance