Washing M/C Water, Dirty clothes, Electrical energy Hot water, Noise, Steam, Clean clothes
TV Electrical energy, Digital signal Picture, Sound, Heat
Sub-Systems Sometimes it is necessary to break the PROCESS down into smaller pieces.
To enable this we consider the system’s
Example: A battery powered torch Switch Bulb Chemical energy Light and Heat energy System Boundary
Pupil Problems 1) A microwave oven Timer Magnetron Electrical energy Heat, Light, Hot food On/Off Turntable Food 1 st Inputs 2 nd Subsystems 3 rd Boundary 4 th Flow of information arrows 5 th outputs Set time
Pupil Problems 2) Washing machine Heater Motor Electrical energy Clean Clothes Control Dirty clothes Pump Drum Water Hot water,etc. Set Cycle
State three examples of manual open-loop control. Draw a system diagram for each one and show the system boundary.
State three examples of manual closed-loop control. Draw a system diagram and show the system boundary.
State three examples of automatic closed-loop control. Draw a system diagram and show the system boundary.
Control Diagrams Example: Temperature control in a gas oven We could draw a systems diagram for the gas oven, but it is sometimes necessary to draw a more accurate control diagram Temperature sensor Oven Burner Gas Valve - + Set value Correct temperature Actual value
Error Detector Symbol - + Set value Actual value Error How the error detector works: If SET VALUE (+) is bigger than the ACTUAL VALUE (-) the ERROR SIGNAL is ON (Raising the oven temperature) If the SET VALUE (+) is less than the ACTUAL VALUE (-) the ERROR SIGNAL is OFF (Cooling the oven temperature)