Variable resistor basics

variable resistors are used as volume control and also for other controls in radio and TV sets. They are also referred as "pots". For high power application fixed wire wound resistor and for low power application fixed carbon resistor of high value is used.

variable resistor

As shown in the figure, variable resistor will have three tags viz. two outer one and one at the center. A wiper makes contact with the track which is connected with center tag. Rotation of the spindle moves the wiper over the track which changes the resistance between the center tag and the end ones. slide type variable resistors will have straight track.

There are different types viz. linear and log. In linear type, change in resistance is proportional to angle. In log type, change in resistance at one end of track is less than at the other for equal angular positions.

Variable resistors are available with typical maximum values which include 10KOhm, 50KOhm, 100KOhm, 500KOhm and 1MOhm. These devices often referred as potentiometers are tuned as per resitance value needed using screwdriver.

Variable resistor is used for following functions:
•  As rheostat to control the current in the electronic circuit.
•  As voltage divider to obtain any voltage from zero to maximum of supply voltage.

Variable resistor manufacturers

Following are few of the reputed variable resistor manufacturers also referred as trimmers, potentiometers and rheostats.
1. vishay
2. Hindustan Electronic Components
3. Jameco Electronics
4. Mouser Electronics
5. Ohmite
6. CTS
7. NTE Electronics Inc.
8. Murata electronics
9. ACP
10. C & K Components
11. Nobel
12. Omite
13. TOCOS America
14. P3 America


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