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What we know — potentiometer

A potentiometer lets us change its output voltage manually, by rotating it.

From “zero” to “full,” we can describe its position as a percentage.
We can also describe that rotation as an angle.

• 0° → 0% → no output voltage.
• 90° → 50% → half the supply voltage.
• 180° → 100% → full supply voltage.

Our example: a linear potentiometer with 180° travel, connected between GND and 5V, with an unloaded output.

What we know — PWM

PWM controls the percentage of time the output is ON.
Arduino expresses that setting as a number from 0 to 255.

• 0 → always OFF → LED off.
• 128 → ON about half the time → LED dimmer.
• 255 → always ON → LED fully bright.

Half the ON time does not necessarily look half as bright.

Put the scales together

For our 5V example:

This table connects familiar scales. The servo’s actual command uses pulse duration — we’ll connect that next.