1. Control Systems Did you get these? Washing machine Microwave cooker
Dishwasher
Fridge
Video recorder

2. Control Systems Did you get these? Remote control for television
Central heating system
Burglar alarm system
Car alarm
External security light

3. Input, Process, Output
INPUT: something that puts information into the system e.g. a keyboard
OUTPUT: something that shows the information that comes out of the system e.g. a printer
PROCESSOR: the part of the system that takes decisions (turn off, turn on...)

5. How Central Heating Works
We want to keep the room at 22ºC.
The thermostat takes regular temperature readings in the room and sends the readings to the control panel.
The control panel looks at the data to see if it matches the ideal 22ºC.

6. Central Heating
If it is lower e.g. 20ºC, then the control panel decides to turn the heating on.
If it is higher e.g. 24ºC, the control panel turns the heating off or turns the air conditioning on.
This decision making is called processing.

8. Wait for microwave to finish
Open Loop Systems
Only look at their input signals when deciding what to do (ignore what is happening to its output).
e.g. programming a video recorder
e.g. setting the microwave
Set time on microwave
Press ON
Wait for microwave to finish
START
STOP

9. Closed Loop Systems
Keep working continuously (don’t just stop after one decision has been made)
'Listen' to their own outputs and act on them
e.g. a central heating system
e.g. a watering system in a greenhouse
Listening to your own output is called feedback

10. COMFORTABLE TEMPERATURE
Closed Loop Systems
Thermostat decides...
Too hot
Heating OFF Air con ON
COMFORTABLE TEMPERATURE
Heating ON Air con OFF
Too hot
Thermostat decides...