Control Logic/Process Logic Summary and Worked out Example 2 Natalie Duchene Jeff Byrd Seung Youn Lyu

Logic Controls IF-THEN Statements “IF” states the condition to evaluate that determines whether an additional step is taken “THEN” states the next step to take if the condition is true Parameters defined with constants or with set values EX:IF T < T1 THEN close V 1 (using a constant) IF T < 200°C THEN close V 1 (using a set value)

Logic Controls Continued ELSE Statements “ELSE” states the alternative step for an IF-THEN statement ELSE statement followed when IF condition is false EX:IF T < 200°C THEN close V 1 ELSE open V 2 V 2 will open only when T is less than 200°C

Logic Controls Continued IF-AND Statements Both the IF condition, as well as the AND condition must be true to continue WHILE statements used in place of IF-AND statements for efficiency EX:IF T > 100°C AND IF T < 200°C THEN close V 3 V 3 will close when T is between 100°C and 200°C

Logic Controls Continued WHILE Statements Simpler than multiple IF-AND statements Allows once to compare variable (T) to a range of values EX:WHILE 100°C < T < 200°C THEN close V 3 V 3 will close when T is between 100°C and 200°C

Worked out Example 2 Temperature control for a simulated cell on a computer chip

Chip has to remain at temperature between 96°F to 98°F Chip is attached to a thermostat Automatic switches/valves: – S1 controls the power supply of the chip – V1 controls the flow of cold water for cooling – V2 controls the flow of warm water for heating Worked out Example 2 Continued

Controlled Logic Scheme When the temperature gets out of range of 96 to 98°F, the power supply needs to be shut off: WHILE (96<T<98) S1 is on ELSE S1 is off Chip may have to be heated or cooled depending on the temperature state: – When temperature of the chip is above 98, cooling valve has to be open: IF (T>98) THEN V2 is open ELSE V2 is closed – When temperature of the chip is below 96, heating valve has to be open: IF (T<96) THEN V1 is open ELSE V1 is closed

Thank you!