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Design & Technology

Components

Light-emitting diode (LED)

A white LED light

A light-emitting diode (LED) is a special kind of diode that glows when electricity passes through it. Most LEDs are made from a semi-conducting material called gallium arsenide phosphide.

LEDs can be bought in a range of colours. They can also be bought in forms that will switch between two colours (bi-colour), three colours (tri-colour) or emit infra-red light.

In common with all diodes, the LED will only allow current to pass in one direction. The cathode is normally indicated by a flat side on the casing and the anode is normally indicated by a slightly longer leg. The current required to power an LED is usually around 20 mA.

Seven-segment LED displays

Seven-segment LCD alarm clock

A seven-segment LED is a special type of LED display used in digital clocks, video recorders and microwave ovens.

Other output devices

  • Like LEDs and seven-segment displays, lamps also convert electricity into light.
  • Piezo sounders, buzzers, bells, loudspeakers and sirens are used to convert electricity into sound.
  • Microphones convert sound into electricity.
  • Solenoids are used to convert electricity into linear movement.
  • Motors convert electricity into rotary movement.

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