Systems Approach Universal System All systems can be

Systems Approach Universal System =All systems can be analysed and simplified in terms of their inputs, process and outputs =The UNIVERSAL SYSTEMS DIAGRAM consists of these three basic elements. =This process is known as the “BLACK BOX” approach to technology =We use a systems diagram to analyse technology. INPUT PROCESS OUTPUT

Systems Diagrams §To analyse a system more fully, we can list the inputs and outputs from the system. As an example, consider an electric kettle, INPUTS: Water and Electricity. OUTPUTS: Hot water, noise, steam. Water and Electricity KETTLE Hot water, Noise and Steam

Pupil Problems Here are some problems for you to try, 1) Battery powered torch Chemical energy Torch Light energy Heat energy 2) Vacuum cleaner Electrical energy Dirt Vacuum Noise, Heat, Clean carpets

Pupil Problems 3) Washing machine Water, Dirty clothes, Electrical energy Washing M/C Hot water, Noise, Steam, Clean clothes 4) Television Electrical energy, Digital signal TV 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 SUB SYSTEMS Example: A battery powered torch Chemical energy Switch Bulb System Boundary Light and Heat energy

Pupil Problems 1) A microwave oven Inputs Set time 2 nd Subsystems 1 st Electrical energy 3 rd Boundary Timer 5 th outputs Magnetron On/Off Turntable Heat, Light, Hot food Food 4 th Flow of information arrows

Pupil Problems 2) Washing machine Electrical energy Water Set Cycle Control Heater Motor Drum Dirty clothes Pump Hot water Clean Clothes

Control Systems §All types of system need some form of control to operate §There are 2 main types of control, OPEN LOOP and CLOSED LOOP §In an OPEN LOOP system the input causes the output §The output operates independently of the input §Open loop system are cheap but not very accurate Action Light switch Bulb Light

Control Systems §In a CLOSED LOOP system, the output is compared with a reference value §Closed loop systems are more accurate, but also more expensive §The self monitoring action of closed loop is achieved through a FEEDBACK loop Set temp Thermostat Heat On/Off Elect Motor Fan Heater

Control Systems Manual Open Loop Water Tap Handle Person Valve Water level Flood

Control Systems Manual Closed Loop Correct level Water Tap Handle Hand Valve Water level Eyes / Brain

Control Systems Automatic Closed Loop Water Correct Temp Required Temperature Heating Switch Control Unit Valve Boiler Temp Sensor

Pupil Problems • 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.