Inputs
Design & Technology: AQA GCSE, topic 1.4.1
Inputs: Sensors
Inputs are things that are put in to the system. They can be activated mechanically (e.g. a switch), or sense a change (e.g. sensor).
Systems
- Electronic systems are broken down into stages.
- The main stages are the inputs, processes and outputs.
- Systems diagrams tend to be drawn as flow charts.
System diagram
Light sensors
- Component name: Light dependent resistor (LDR).
- A light sensor that is sensitive to a change in light.
- Its resistance increases in the dark so can act as a switch turning on street lights in the dark and off in the light.
Component symbol: light sensors
Temperature sensor
- Component name: Thermistor.
- A temperature sensor that is sensitive to a change in temperature.
- Its resistance increases with a change in temperature so can act as a switch turning the oven on when it is too cold and off when it has reached the desired temperature.
Component symbol: temperature sensor
Inputs: Switches
Inputs are things that are put in to the system. They can be activated mechanically (e.g. a switch), or sense a change (e.g. sensor).
Switches
- Mechanical switches are added to systems, allowing them to be turned on and off.
Pressure switch
- Component name: Pressure switch.
- A pressure switch is sensitive to a pressure or weight being applied.
- It can be used in cars to remind the driver to fasten their seat belt.
Component symbol: pressure switch
Toggle switch
- Component name: Toggle switch.
- Once switched on a toggle switch will complete the circuit and it will remain on until it is turned off and the circuit is broken.
- It is used for light switches.
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Component symbol: toggle switch
Push to make (PTM) switch
- Component name: Push to make (PTM) switch.
- This circuit is usually off and when you push the switch the circuit is completed and turned on.
- A good example of this is the door bell, whereby it rings when pushed.
Component symbol: PTM switch
Push to break (PTB) switch
- Component name: Push to break (PTB) switch.
- This circuit is usually on and when you push the switch the circuit is broken and turned off.
- This can be used in a lift when the user wants the door to be kept open for longer by pressing a button.
Component symbol: PTB switch
Test yourself on Inputs
Which of the following appliances is likely to have a thermistor?
What does LDR stand for in relation to inputs?
What type of switch is used for light switches?