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Potentiometers adjust electricity flow in devices. Analog potentiometers modulate circuits by controlling power flow, while digital potentiometers are controlled by digital signals and convert them to analog output. Digital potentiometers have limitations in modulation and voltage range, but some have onboard memory to remember settings.
A potentiometer is used to adjust the general level of electricity passing through a device. Typically used in items such as volume control knobs and light dimmers, standard analog potentiometers allow an individual to modulate the responsiveness of a circuit, by controlling the flow of power within it. A digital potentiometer, or digipot, is controlled entirely by digital signals; in use, these signals are converted to an analog output, allowing the user to control the electrical signal. Digital potentiometers are typically used to modulate analog signals in microcontrollers, such as the central processing units in a computer. By controlling the amount of power passing through the microcontrollers, the potentiometer works to keep the power flowing through sensitive electronic devices in tight control.
Digital potentiometers are constructed using R-2R ladder integrated circuits or using a direct digital-to-analog converter. Either way, these devices take the digital binary code generated by the digital potentiometer and translate it into an analog voltage signal for the device. This results in the correct amount of power being transferred to the device, allowing modulations to be made through nothing more than adjustments to the digital signal moving through the device.
Compared with traditional potentiometers, digital potentiometers have some shortcomings. The first of these is modulation; digital signals cannot be adjusted as finely as analog signals, resulting in adjustments that cannot be made as precisely. The most common are 256-step digital potentiometers, but ones ranging from 32 to over 1,000 steps are also available. Another drawback is the limitation to their digital supply voltage range, which typically runs from 0 to 5 volts direct current (VDC), lower than the standard range of most analog potentiometers. Occasionally, during a ignition cycle, a digital potentiometer will default to a random value, which can potentially cause circuit problems.
Some versions of a digital potentiometer contain onboard memory. This allows them to remember their specific setting even after the flow of energy moving through the device has been disrupted, such as by a user turning off a computer or other electrical device. For these types of digital potentiometers, as soon as they are turned on again, they immediately resume operating at the exact power level they were at before the power was turned off.
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