Trimpot

 
Trimpot

What is a trimpot? A trimpot or trimmer potentiometer is a small potentiometer which is used for adjustment, tuning and calibration in circuits. When they are used as a variable resistance (wired as a rheostat) they are called preset resistors. Trimpots or presets are normally mounted on printed circuit boards and adjusted by using a screwdriver. The material they use as a resistive track is varying, but the most common is either carbon composition or cermet. Trimpots are designed for occasional adjustment and can often achieve a high resolution when using multi-turn setting screws. When trimmer potentiometers are used as a replacement for normal potentiometers, care should be taken as their designed lifespan is often only 200 cycles. Trimpot definition Trimmer potentiometers and preset resistors are small variable resistors which are used in circuits for tuning and (re)calibration. Types of trimpots Several different versions of trimpots are available, using different mounting methods (through hole, smd) and adjusting orientations (top, side) as well as single and multi-turn variations. Single turn Single turn trimmers/presets are very common and used where a resolution of one turn is sufficient. They are the most cost effective variable resistors available. Multi turn For higher adjustment resolutions, multi-turn trimpots are used. The amount of turns varies between roughly 5-25, but 5, 12 or 25 turns are quite common. They are often constructed using a worm-gear (rotary track) or leadscrew (linear track) mechanism to achieve the high resolution. Because of their more complex construction and manufacturing, they are more costly than single turn preset resistors. The lead screw packages can have a higher power rating because of their increased surface area. Trimpot symbols The following IEC symbols are used for trimpots and preset resistors. Although this are the official symbols for occasionally adjusted resistors, the standard symbols for [… read more]

Potentiometer

 
Potentiometer

What is a potentiometer? A potentiometer is a manually adjustable variable resistor with 3 terminals. Two terminals are connected to both ends of a resistive element, and the third terminal connects to a sliding contact, called a wiper, moving over the resistive element. The position of the wiper determines the output voltage of the potentiometer. The potentiometer essentially functions as a variable voltage divider. The resistive element can be seen as two resistors in series(potentiometer resistance), where the wiper position determines the resistance ratio of the first resistor to the second resistor. A potentiometer is also commonly known as a potmeter or pot. The most common form of potmeter is the single turn rotary potmeter. This type of pot is often used in audio volume control (logarithmic taper) as well as many other applications. Different materials are used to construct potentiometers, including carbon composition, cermet, wirewound, conductive plastic or metal film. Potentiometer definition A potentiometer is a manually adjustable, variable resistor with three terminals. Two terminals are connected to a resistive element, the third terminal is connected to an adjustable wiper. The position of the wiper determines the output voltage. Types of potentiometers A wide variety of potmeters exist. Manually adjustable potmeters can be divided in rotary or linear movement types. The tables below list the available types and their applications. Besides manually adjustable pots, also electronically controlled potentiometers exist, often called digital potmeters. Rotary potentiometers The most common type of potentiometer where the wiper moves along a circular path. Type Description Applications Single-turn pot Single rotation of approximately 270 degrees or 3/4 of a full turn Most common pot, used in applications where a single turn provides enough control resolution. Multi-turn pot Multiple rotations (mostly 5, 10 or 20), for increased precision. They are constructed either with a wiper [… read more]