Transducers
A transducer is a device which converts a signal from one form to another.
Most electronics circuits use both input and output 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.
Examples:
Output Transducers convert an electrical signal to another quantity.
Examples:
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.
Please see the next page for more information about voltage dividers.
Most electronics circuits use both input and output transducers:

Input Transducers
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LDR Photograph © Rapid Electronics |
- LDR converts brightness (of light) to resistance.
- Thermistor converts temperature to resistance.
- Microphone converts sound to voltage.
- Variable resistor converts position (angle) to resistance.
Output Transducers
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Loudspeaker Photograph © Rapid Electronics |
- Lamp converts electricity to light.
- LED converts electricity to light.
- Loudspeaker converts electricity to sound.
- Motor converts electricity to motion.
- Heater converts electricity to heat.
Using input transducers (sensors)
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Voltage divider circuit |
The conversion of varying resistance to varying voltage is performed by a simple circuit called a voltage divider.
Please see the next page for more information about voltage dividers.
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