concept potentiometer in category arduino

This is an excerpt from Manning's book Arduino in Action. Login to get full access to this book.

3.1.2. Reading a potentiometer

A potentiometer is one of the simplest ways to show how the Arduino’s analog input works. Potentiometers come in all shapes and sizes, as shown in figure 3.1, and they’re used in many different devices all around us. If you have a stereo with a rotary volume control, it’s likely based on turning a potentiometer. Other examples include dimmer controls on lights and temperature controls on electric cookers or ovens. Despite the different shapes and sizes, they all have some means of varying resistance, either in a linear or logarithmic way.

Figure 3.1. A selection of potentiometers

The majority of potentiometers have three connections; the middle one is usually called the wiper and is used to vary the resistance by moving a contact along a fixed resistor. For this chapter, you want a potentiometer that varies resistance linearly and that’s suitable for plugging into a breadboard; trimpots are often ideal.

Figure 3.2 shows the schematic symbols for a potentiometer. The central arrow, known as the wiper, is overlaid over the standard symbol for a resistor and indicates that the resistance is variable.

Figure 3.2. Schematic symbols for a potentiometer: U.S. (left), International (center), Fritzing (right)

Let’s now move on to connecting a potentiometer to the Arduino.