Potentiometers
A potentiometer
is simply a variable resistor that can be controlled by the user.
Potentiometers accomplish this by having three terminal resistors forming and a
load that connect the potentiometer and the voltage source in one loop and the
potentiometer and the load in another. Potentiometers have a wide range of
uses, ranging from CD players to Servo mechanisms.
How Does a Potentiometer
Work?
A potentiometer has 3 pins. Two
terminals (the blue and green) are connected to a resistive element and the
third terminal (the black one) is connected to an adjustable wiper. The
potentiometer will work as a rheostat (variable resistor) or as a voltage
divider.
Rheostat
To use the potentiometer as a
rheostat, only two pins are used: one outside pin and the center pin. The
position of the wiper determines what quantity resistance the potentiometer is
imposing to the circuit, as the figure demonstrates:
If we have a 10kΩ potentiometer, it
means that the maximum resistance of the variable resistor is 10kΩ and the
minimum is 0Ω. This means that by changing the wiper position, you get a value
between 0Ω and 10kΩ.
Voltage Divider
Potentiometers can be used as
voltage dividers. To use the potentiometer as a voltage divider, all the 3 pins
ar connected. One of the outer pins is connected to the GND, the other to Vcc
and the middle pin is the voltage output.
When the potentiometer is employed
as a voltage divider, the wiper position determines the output voltage. When
you have the potentiometer connected this way, you have the following circuit:
Basically, the voltage divider is
employed to show an oversized voltage into a smaller one.
Potentiometer Taper
One main thought related to potentiometers
is that the taper. The taper is the relationship between the position and the
resistance of the potentiometer. The most common types are linear and
logarithmic tapers.
Linear potentiometers
The most common form is the simple
linear taper. In a linear taper, the relationship between the resistance and
the potentiometer position is linear. This means that if the knob of the
potentiometer is at the medium position, the output voltage is half of the
voltage through the potentiometer.
Logarithmic
potentiometers
Non-linear tapers are specially
used in audio control applications, namely logarithmic tapers (there are also
inverse-logarithmic tapers).
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