1. Systems Approach Universal System  We use a systems diagram to analyse technology.  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 PROCESS INPUTOUTPUT

2. 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, OUTPUTS: KETTLE Water and Electricity Hot water, Noise and Steam Water and Electricity. Hot water, noise, steam. INPUTS:

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

4. Pupil Problems 3)Washing machine Washing M/C Water, Dirty clothes, Electrical energy Hot water, Noise, Steam, Clean clothes 4)Television TV Electrical energy, Digital signal Picture, Sound, Heat

5. 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 SwitchBulb Chemical energy Light and Heat energy System Boundary

6. 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

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

8. Control Systems  All types of system need some form of control to operate  There are 2 main types of control, OPEN LOOP  In an OPEN LOOP system the input causes the output  The output operates independently of the input CLOSED LOOPand  Open loop system are cheap but not very accurate Light switchBulbActionLight

9. 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 On/OffMotorFanHeater Thermostat Set temp Elect Heat

10. Control Systems Tap Handle ValveWater level Water Person Flood Manual Open Loop

11. Control Systems Tap Handle ValveWater level Water Eyes / Brain Hand Correct level Manual Closed Loop

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

13. 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.