Control Systems

Did you get these? Washing machine Microwave cooker Dishwasher Fridge Video recorder

Control Systems

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

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...)

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.

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.

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

STARTSet time

onmicrowave

PressON

Wait formicrowave

to finishSTOP

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

Closed Loop Systems

COMFORTABLETEMPERATURE

Too hot

Too hot

Thermostatdecides...

Thermostatdecides...

Heating OFFAir con ON

Heating ONAir con OFF