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Introduction to Microcontroller Programming

About PICmicro Chips

Clocking Your PICmicro Devices


Flowcode Step By Step

PICmicro Projects



An electronic control system knows nothing about the outside world unless we give it sensors - its eyes, ears etc. The language it understands is that of electrical signals, voltages and currents.

A sensor has to turn changes in the outside world, such as light level, temperature, sound level, humidity, pressure etc., into changing electrical signals. A different type of sensor is needed for each of these tasks.

Here are some of them.

Light sensor:

The light dependent resistor (LDR) - Its resistance drops when a brighter light shines on it. It is relatively slow to react to changes in light level, though.

The photodiode - A component that passes an electric current only when sufficient light shines on it. It reacts much faster than the LDR to changes in light level.

Temperature sensor:

The thermistor - There are two versions of thermistor. One type, called ntc (negative temperature coefficient) has a resistance that gets less when its temperature goes up. The other type, ptc, (positive temperature coefficient) has a resistance which gets bigger when the temperature rises.

Sound sensor:

The microphone - The common form of microphone generates a voltage when it picks up a sound. The louder the sound, the bigger the voltage!

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Page last modified on August 26, 2011, at 10:42 AM