What Is a Trimmer Potentiometer?
A trimmer potentiometer is a variable resistor whose resistance value can be changed.
They are also called trimmer resistors or trim potentiometers because of their role in adjusting (trimming) the resistance value of a circuit in an electronic device. They adjust for variations due to individual differences in other electronic components.
The resistance of a trimmer potentiometer is adjusted by turning a knob with a driver. There are two types: top-turned and side-turned, and single-turn and multi-turn knobs.
Applications of Trimmer Potentiometers
Trimmer potentiometers are used in a variety of products, including communications equipment, measuring instruments, medical equipment, audiovisual equipment, office equipment, and general electronic equipment. They are applied in situations such as post-production timing adjustment, temperature adjustment, and display brightness adjustment.
Typically, once set, they operate as fixed resistors without being seen by the end user, but they may need to be readjusted during maintenance.
Trimmer potentiometers are often used in hobbyist electronics work, as they are useful for fine-tuning circuit boards.
Principle of Trimmer Potentiometers
The principle of the trimmer potentiometer is simple. When voltage is applied to both terminals (terminals 1 and 3) of a resistive element, the physical position of the contacts (slider or wiper) that move on the resistive element changes the resistance between terminals 2 and 1 (or 3), which is connected to the slider.
A trimmer potentiometer has two roles. Voltage adjustment, in which a larger voltage is lowered to obtain the required voltage. And current adjustment, in which the resistance value is adjusted to change the current value.
When used for voltage adjustment, a trimmer potentiometer is used as a 3-terminal element: voltage is applied between terminals 1 and 3, and the voltage divided by the voltage is taken from terminal 2.
When used for current regulation, a trimmer potentiometer is used as a 2-terminal element, and voltage is applied between terminals 1 and 2 to regulate the current. However, it is safe to leave the unused No. 3 terminal open and connect it to the No. 2 terminal.
The resistance between the two ends of a trimmer potentiometer and the total resistance vary. If the total resistance value is small, the variable range becomes narrower. On the other hand, if the total resistance value is large, the variable range becomes large. However, the setting accuracy becomes lax. Generally, a trimmer potentiometer is selected so that adjustment can be made over a variable range of half the total resistance.