Potentiometers Explained: Types, Tapers, and How to Use Adjustable Resistors

Overview

This video provides a practical introduction to potentiometers, adjustable resistors used to tune voltage and current in electronic circuits. It covers rotary, slider, and trimming variants, how the resistance changes with knob position, and how to use potentiometers as voltage dividers or rheostats. Real world examples include joystick pots in game controllers, servo position sensing, volume control in radios, and RGB LED color control. The presenter also demonstrates measuring resistance with a multimeter and discusses datasheets and taper codes. A sponsor acknowledgement for PCB Way appears in the video description.

What you will learn

You will learn the basic construction, how the three terminals connect to resistive tracks, and how to interpret markings like 1k, 500K, and 1M. The video also explains linear versus logarithmic tapers and why different tapers suit different applications, such as audio volume versus lighting control. Finally, practical tips for testing and implementing potentiometers in your own circuits are covered.

Introduction to Potentiometers

Potentiometers are adjustable resistors used to manually vary resistance in a circuit. They come in several forms, including rotary pots with a shaft and knob, slide pots, and compact trimmers. Each variant shares a common principle: a resistive track runs between two end terminals, with a wiper that slides along the track and connects to the center terminal. Turning the knob or moving the slider changes the wiper position, which in turn changes the resistance between the center pin and the end pins. The outer track is typically the fixed resistance, while the center pin is the wiper output that changes as you adjust the shaft.

How They Work

In a rotary potentiometer, rotating the shaft moves the wiper along the resistive track. The resistance increases or decreases depending on the wiper position and the wiring. The device can be used as a voltage divider, where the input voltage is applied across the two end terminals and the output comes from the center terminal. If you connect a multimeter between the center and one end, you will see a variable voltage proportional to the wiper position. If you measure across the end terminals, you see the total resistance of the track, which is fixed for a given pot.

Taper Codes and Markings

Potentiometers have markings that indicate their maximum resistance and taper type. Common markings include 1k, 500K, and 1M. The first letter on some types indicates taper, with B for linear, A for logarithmic, and C for inverse logarithmic tapers. However, these letters and codes can vary by manufacturer, so consulting the datasheet or testing with a multimeter is wise to confirm behavior. The video demonstrates how linear (B) tapers provide a constant resistance change per degree of rotation, while logarithmic (A) tapers change more gradually at one end and more rapidly at the other, which is useful for audio volume control.

Types of Potentiometers

The video covers several types: rotary potentiometers (two or three terminals, with linear or log tapers), dual (two pots joined on one shaft for stereo control), multi-turn pots (higher precision with more shaft rotations), slide potentiometers (variable resistance via a sliding contact), and trimmer potentiometers (small, for calibration with limited rotation). Multi-turn pots use a gear-disc mechanism to allow many turns, enabling very precise control, while slide pots provide a compact form factor with a linear resistance change along a track. Trimmers are often used for occasional adjustments and have limited movement. Each type has different mounting, power ratings, and durability characteristics that influence their use in circuits.

Using Potentiometers in Circuits

You can use potentiometers as voltage dividers by applying the supply across the two end pins and taking output from the center pin. This allows you to vary the output voltage smoothly by turning the shaft. In rheostat mode, you can use a potentiometer to limit current by placing the wiper output in series with a load. The video emphasizes the importance of not exceeding the device’s power rating and demonstrates a LED brightness control circuit as a practical example. The presenter also discusses how a series resistor is still needed to limit maximum current when using the pot as a rheostat, to prevent damage to the LED if the wiper is turned to the near end of travel.

Practical Projects and Resources

In addition to theory, the video provides practical projects such as controlling colors in an RGB LED with linear-taper potentiometers and offers downloadable PCB project files for free. The content also touches on measuring resistance with a multimeter, checking pinouts, and referencing datasheets for power, voltage, and switching characteristics. For viewers looking to prototype, PCB Way is introduced as a sponsor offering PCB fabrication and assembly services, as well as a project library and related manufacturing capabilities. The video encourages engagement by asking where viewers have encountered potentiometers in real life.

Conclusion and Next Steps

By understanding the structure of potentiometers, their taper types, and how to wire them in typical circuits, you can design precise, adjustable control for voltage and current in a wide range of applications. The video serves as a practical primer for hobbyists and engineers alike and points to additional resources, including downloadable PCB designs and a community of projects to explore.