There are two types of transducers.
|Input Transducers||Output Transducers|
|photoresistors||light emitting diodes|
|and many more....|
Photoresistors are variable resistors. When the light shining on them increases in intensity, their resistance is lowered. Working photoresistors into your circuits will allow you to detect changes in lighting. For example you could build a circuit to beep if someone turned on your room lights.
Thermistors are also variable resistors, however instead of being sensitive to light, they are sensitive to temperature. There are two types of thermistor:
A microphone converts pressure changes (sound) to voltage changes. Speakers are usually used to convert voltage changes to pressure changes (sound), but they can also work the other way. Normally, pressure changes near a microphone do not affect the voltage very much, and the signal must be amplified.
Piezoelectric devices contain special crystals. These crystals will produce a voltage if pressure is applied to them in one direction. The crystals will also bend if voltage is applied to them. A common use of piezoelectric devices are "buzzers", which produce a buzzing noise when a voltage is applied.
Light Emitting Diodes
Light emitting diodes, or LED's as they are usually called, generate light when a current is passed through them. You will learn about diodes in the next section. LED's have many widespread uses.