Potentiometer

Potentiometers are three-terminal resistor with a sliding connection that forms the voltage divider can be set. If only two terminals are used (one fixed terminal and the terminal sliding), the potentiometer acts as a variable resistor or rheostat. Potentiometer is usually used to control electronic devices such as voice control on the amplifier. Potentiometer operated by a mechanism can be used as a transducer, such as a joystick sensor.

Potentiometer is rarely used to control high power (greater than 1 Watt) directly. Potentiometer used to set the standard analog signal (eg voice control on audio devices), and as controller inputs for electronic circuits. For example, a potentiometer for dimming the lamp using a TRIAC switching menendalikan, so indirectly control the brightness of the lights.

Potentiometer used as volume control sometimes equipped with an integrated switch, thus opening the switch when the potentiometer wiper is at the lowest position.

Potentiometers  Construction

A potentiometer is usually made of a semi-circular resistive element with shear connection (sweeper). Resistive element, with terminals at one or both ends, is flat or oblique, and usually made of graphite, although other materials may also be used instead. Sweeper is connected to other terminals. In panel potentiometer, wiper terminal is usually located in the middle of the two terminal resistive element. For a single rotation potentiometer, wiper usually move less than one full rotation during the contact. Potentiometer “double-loop” also exists, perhaps in the form of the element resistifnya wrench and wiper may move 10, 20, or more rounds to complete the cycle. However, double-loop cheap potentiometers are usually made from the same conventional resistive element with a single round of resistors, while the wiper is driven through a worm gear. In addition to graphite, the material used to make the resistive element is a resistance wire, plastic, carbon particles and ceramic-metal mixture called cermets. In the linear slide potentiometer, a slide control is used instead of the control of the play. Resistifnya element is a square path, not a semi-circular path as in turn potentiometer. Potentiometer of this type are often used in graphics tuner devices, such as ekualizer graph. Since there are openings big enough for the sweeper and kenob, this potentiometer has a lower reliability when used in a bad neighborhood.

Potentiometer is available with linear or logarithmic relationship between the sweeper position and the resulting resistance (potentiometer law or “tapers”).

Constructor potentiometers conductive path using conductive polymer resistor paste containing resins and polymers, solvents, lubricants and carbon. Point made by printing the surface of the substrate phenolic papua and roast in oven. Roasting process removes all of the solvent and allow the pasta to be a solid polymer. This process produces durable lines with stable resistance throughout the surgery.

Linear potentiometer

Linear potentiometer resistive element with constant cross section, resulting in devices with a resistance between the wiper with one terminal is proportional to the distance between them .. Linear potentiometer used if desired proportional relationship between the rotation axis with the division ratio of the potentiometer, for example controllers are used to set the oscilloscope screen center point.
[Edit] Logarithmic Potentiometer

Logarithmic potentiometer has a resistive element which progressively narrowed or made from materials that have resistivity varies. This gives a resistance device is a logarithmic function of the potentiometer shaft angle.

Most of the potentiometer log (especially the cheap) is actually not really logarithmic, but uses two linear resistive path to mimic logarithmic law.  log potentiometer can also be made by using a linear potentiometer and an external resistor. Potentiometer is really very expensive relative logarithmic.

Logarithmic potentiometers are often used in the audio devices, especially as the volume control.

Rheostat

The most common way to vary the resistance in a circuit is to use a variable resistor or rheostat. A rheostat is a two terminal variable resistor and is often designed to handle high currents and voltages. Rheostat is usually made of resistive wire coil wrapped around to form a toroid with a wiper that moves at the top of the toroid, touching the coil windings of one coil to the next.

Three-terminal potentiometer can be used as a variable resistor with two terminals are not using a third terminal. Often a third terminal connected to the terminal is not used mops to reduce the resistance fluctuations caused by dirt.

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