Often called Trimpots, these little components are essential for fine-tuning circuits and ensuring your devices function just the way you want. A potentiometer is essentially a variable resistor, which allows you to manually adjust the resistance in a circuit. A trim pot is a type of potentiometer that’s designed for more precise, infrequent adjustments. Think of it as the control knob that you set once and forget. They are used for tuning circuits, setting reference voltages, and setting opamp gains when resistance tolerance needs to be handled post-assembly.

Trimpots have 3 terminals, two connected to the ends of a resistive element, and a third one (the wiper) that slides along the resistive track. By adjusting the wiper, you change the resistance between the wiper and each end of the resistor. What you need to remember is that there will always be a finite resistance between the terminals, it may not always be zero on one end. Refer to the datasheets for the minimum resistance or the terminal resistance for this value. When selecting trimpots, consider the same factors you’d consider when choosing a resistor like resistance tolerance, temperature variation, and power rating. What is extra would be contact variational resistance, which is the max change in contact resistance that will be encountered when the wiper moves from one place to another. We want this to be low. Good quality manufacturers also specify vibrational or shock tolerances.
They come in different shapes and types. The key one is a single turn vs multi-turn. It specifies the number of rotations you need to full resistance range. Multiturns are expensive but offer precise control of resistance for fine-tuning. It comes in open frame or sealed packages(useful in high humidity cases).
A common mistake I see among clients is using trimpots(as they are smaller) where rotary potentiometers should be used. Trimpots have a notoriously short lifespan (100-200 cycles) compared to rotary pots (about 10k cycles). Always check the datasheet for cycles! If the knob will be adjusted often, use a rotary pot.
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