Design & Technology Resources
©2019 E.Clarvis
An output transducer is simply a component that converts electrical energy into light, sound, movement or heat.
A piezoelectric transducer is a very simple type of speaker that can be used to produce high pitched sounds. They are used in musical Christmas cards and the sirens in smoke alarms. To make them work you usually need to connect them to the output of an astable circuit.

A piezoelectric transducer can also be used to generate electricity. If the transducer is squeezed it will actually produce a pulse of electricity. They are  used in some lighters to produce a spark which ignites the gas. For more information click on the link for smart materials
A DC Motor converts an electric current into rotational movement. When we use them in an electronic circuit we usually have to use a transistor to drive them because they need quite a high current. Look at the transistors section of this web site to find out about this.
A filament lamp (commonly known as a light bulb) converts electrical energy into light.

They contain a thin coil of tungsten that gets so hot when current is passed through it actually glows, this is called incandescence. Lamps have a relatively short life and are easily damaged by shock, They are also very inefficient, the majority of the energy produced is in the form of heat rather than light.

They are gradually being replaced by LEDs in many applications including car indicators and brake lights.

This is because they are much more efficient, have a longer life and are not damaged by physical shock.
A speaker is a device that takes in an electrical signal and converts it into sound. It consists of a cardboard diaphragm, a magnet and a coil of wire. The come in a wide range of sizes and powers.

If we were to connect a speaker to the output of an astable circuit the speaker can be made to produce a tone.
Circuit Symbol
Circuit Symbol
An LED is a type of diode which lights up when a current flows through it. As mentioned above they are much more efficient than incandescent lamps (normal electric light bulbs).

When LEDs were first developed only a few different colours were available. Now there are even pink and ultraviolet LEDs.

RGB LEDs are available which consist of three LEDs in one: red, green and blue. By controlling the brightness of each LED any visible colour can be created! Flashing LEDs are also available.
Circuit Symbol
Piezoelectric Transducers
Output Components
Circuit Symbol
Light Emitting Diodes (LEDs)

Longer lead

Shorter lead
Flat side
The cathode is identified in two different ways: Shorter lead and the flat side on the body of the LED.
Televisions are now manufactured that use LEDs to produce the picture, they have a high contrast and are much more efficient than the older CRT type (the ones with a tube). The picture on the left shows an LED screen designed for use at the Beijing Olympics. It uses 2929 RGB leds!

The picture below shows the fountain in front of Sheffield railway station illuminated by LEDs
A buzzer is much simpler than a piezoelectric transducer or a speaker. To make it buzz all you have to do is connect it up to a battery. It is a polarised  component which means it must be wired up the right way around.
Circuit Symbol
Buzzers and Sounders
7-Segment LED Displays

A 7-Segment display is made up of seven rectangular LEDs arranged in a figure of 8 pattern. By lighting up the LEDs in the right order it is possible to get them to display the numbers 0 to 9.


An integrated circuit (IC) is available called a 4026 which allows you to build a counter that will increase its value every time it receives a clock pulse. This pulse could come from a switch of some kind or the output of an other circuit, like an astable circuit for example. To see how a 4026 works click on this link:

4026 7-Segment Counter
A buzzer is much simpler than a piezoelectric transducer or a speaker. To make it buzz all you have to do is connect it up to a battery. It is a polarised  component which means it must be wired up the right way around.

Expansion spring

Iron rod

Copper coil


A solenoid is an output component that converts electrical energy into linear movement. Normally the rod is pushed out by the spring. When the coil is connected to a battery it works like an electromagnet and pulls the rod into the casing. Once the power is disconnected the electromagnet turns off and the rod extends again.


Solenoids are used in water valves that turn the water on and off depending one whether the coil is turned on or off.



When the power to a coil is switched off a large voltage is produced called a back EMF. This high voltage can damage components like transistors and Ics. A blocking diode is needed in a circuit using a solenoid to prevent this damage, the diagram below shows this:

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Blocking diode

Smart Materials
Smart Materials
Light Emitting
Diodes (LEDs)
Light Emitting Diodes

Click here for more detailed information on LEDs.