Rotary Potentiometers
About rotary potentiometers
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What is a rotary potentiometer?
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Rotary axis and attachment of rotary potentiometers
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Resistance values and load capacity
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Notes on manufacturing
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What types and types of rotary potentiometers are available?
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Purchase criteria for rotary potentiometers
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FAQ – frequently asked questions about rotary potentiometers
What is a rotary potentiometer?
Rotary potentiometers are adjustable electrical resistors which are used to implement control procedures in electrical and electronic systems , for example for volume control in a radio. Potentiometers consist of a support on which the resistor material is applied.
For rotary potentiometers, the resistance material is usually flat and circular . At both ends there are electrical connections for screwing, plugging or soldering. A sliding contact, the so-called grinder, is moved on the resistor material by means of a rotary axis. Depending on the angular position of the rotating contact to one of the connections, a defined electrical resistance is achieved between the connection and the slider position. The maximum rotation angle is approximately 300 degrees. However, there are also special versions, so-called multi-turn potentiometers, in which the resistance material is arranged in a spiral so that the grinder can perform several revolutions by 360 degrees. Special models are equipped with drive motors that can be used to implement remote control . Depending on the resistor material used, different power ranges are possible. The material used also influences the durability of the rotary potentiometer. For operation, the slider is led out of the potentiometer with an axis. The axle can have different versions so that it can be attached to its control buttons. The axis has a slot/cross for screwdriver for the rarely necessary settings. For simultaneous control processes, several rotary potentiometers can be arranged one after the other and connected to a completed axis. An example is the volume control of a stereo amplifier.
Rotary axis and attachment of rotary potentiometers
In many rotary potentiometers, the rotary axis is surrounded by a threaded piece that allows the potentiometer to be attached to a support such as the implement housing or an installation angle. Most potentiometer models are surrounded by a housing that is either fixed to the thread or can be soldered onto PCBs . Additional elements are often placed on the thread itself or on the housing, with which the entire rotary potentiometer is secured against twisting when reaching the end position.
Resistance values and load capacity
Rotary potentiometers are available in a wide range of resistance values from 4.7 ohms to 4.7 megohm. The load capacity ranges from 0.05 to 170 watts. There are also rotary potentiometers with switch function in one of the end positions of the slider as well as with latching rotary positions.
Notes on manufacturing
In production, manufacturers must comply with limit values for substances that are hazardous to health and that are hazardous to the environment. Directive 2011/65/EU of the European Parliament and of the Council of 8 June 2011 on the restriction of the use of certain hazardous substances in electrical and electronic equipment is in place. The non-official designation is RoHS 2.
What types and types of rotary potentiometers are available?
Linear rotary potentiometer
For rotary potentiometers with linear resistance characteristic, the resistance changes proportionally to the angle of rotation.
Logarithmic rotary potentiometer
In this version, when turning, only a small resistance value is initially changed, then the resistance value per degree angle of rotation is always increased and vice versa. Volume controls are a classic application. The decibel scale is converted as a measure of the volume, which also has a logarithmic curve.
Special rotary potentiometer
These are rotary potentiometers with special properties, such as dust protection and very high precision.
Thread dimensions
Threaded devices are available in inch sizes, starting with 3/8 inch and with metric thread dimensions M7 to M10. The latter is most frequently represented.
Axle diameter
The axle diameter ranges from 3 millimeters to 6.35 millimeters. The most common axle diameter in the Conrad range is 6 millimeters.
Axle design
The design of the axis influences the way the potentiometer is operated. Conrad has:
- Flattened ends for screwing on control elements
- Corrugated axes for direct operation or for attaching control elements
- Slotted axles for screwdriver
- Smooth axes for screwing control elements into place
- round axes for screwing on control elements
- Plastic axles, which can be guided to the outside in isolation and
- Metal axles for high stability
Purchase criteria for rotary potentiometers
In addition to the high precision of the specified resistance values, rotary potentiometers should offer a good compromise between smooth running and torque to be used for motion. For some models, there is information in the product description or in the data sheet. The data sheets contain information on durability, which can range up to turning cycles in the middle five-digit range. When developing new devices, the data sheets of the suppliers help to find the exact rotary potentiometer suitable for the desired application area.
With industrial packaging in large quantities, favorable purchase prices can be achieved.
FAQ – frequently asked questions about rotary potentiometers
What should be taken into account when replacing rotary potentiometers?
The replacement of potentiometers should only be carried out by qualified personnel, as if the potentiometers are not removed or unsoldered properly, this can cause considerable damage to the devices concerned. When replacing the potentiometer, make sure that the replacement potentiometer has exactly the same performance characteristics. The rotary potentiometers offered meet high quality standards and are characterized by reliability and long life. In any case, pay attention to existing warranty claims. The manufacturer's warranty will generally be void in the event of interference with the device. The general safety rules of electrical engineering must be observed.
How do I know that a rotary potentiometer is defective?
Defective rotary potentiometers are usually indicated by one of the following problems:
- Crackling or rustling while changing the volume
- Stiff axle
- Loose mounting
- "Spin" without control influence by removing the slider from the axis
This is due to the wear of mechanical components.