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A transducer is a device which converts a signal from one form to another. Most electronics circuits use both input and output transducers:

simple electronic system

Input Transducers


Input Transducers convert a quantity to an electrical signal (voltage) or to resistance (which can be converted to voltage). Input transducers are also called sensors.


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LDR photograph © Rapid Electronics

Output Transducers


Output Transducers convert an electrical signal to another quantity.


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Loudspeaker photograph © Rapid Electronics

Using input transducers (sensors)

Most input transducers (sensors) vary their resistance and this can be used directly in some circuits but it is usually converted to an electrical signal in the form of a voltage.

The voltage signal can be fed to other parts of the circuit, such as the input to an IC or a transistor switch.

The conversion of varying resistance to varying voltage is performed by a simple circuit called a voltage divider.

voltage divider with LDR at top

Voltage divider circuit

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