# @stem_antics on Instagram

- **Type:** Video
- **Original URL:** https://www.instagram.com/p/DY8-qP5gFLu
- **Gondola URL:** https://gondola.cc/posts/66053059-stem-antics-instagram
- **Thumbnail:** https://img.gondola.cc/tr:w-,h-,fo-auto/postThumbnails/26a5c3de5e.jpg
- **Posted:** 2026-05-30T14:49:47.000+00:00
- **Account Owner:** Stem Antics (@stem_antics) — https://gondola.cc/stem_antics

## Caption

Twist a volume knob and you may be turning one of two devices that look nearly identical from the outside. The split between a potentiometer and a rotary encoder is one of the cleaner illustrations of analog versus digital position sensing.

A potentiometer is fundamentally a variable resistor. A wiper slides across a resistive track, dividing it into two halves and forming a voltage divider. The output is a continuous analog voltage that maps directly to shaft angle. This makes it inherently absolute: power up the circuit and the voltage already tells you exactly where the shaft sits. The tradeoffs all follow from that sliding physical contact:

	•	Rotation is bounded, typically around 270 degrees for a single turn
	•	The wiper wears over time, eventually producing scratchy, noisy output
	•	Resolution is limited only by the ADC reading it, but so is the noise floor

A rotary encoder reports motion digitally. Incremental encoders output two square waves, channels A and B, held 90 degrees out of phase. This quadrature scheme is elegant: the order in which the edges arrive reveals direction, and counting those edges reveals distance. Decoding all four transitions per cycle yields four counts per pulse, the distinction between PPR and CPR.

The contrasts run deep:

	•	Encoders spin continuously with no mechanical end stop
	•	Incremental types are relative and lose position on power loss unless homed
	•	Absolute encoders assign each position a unique Gray code, where only one bit changes per step to prevent transition errors
	•	Optical and magnetic variants avoid wiping contact entirely, extending lifespan dramatically

The choice is rarely about which one wins. A pot hands you absolute position for free on a single analog pin. An encoder demands a microcontroller and counting logic but rewards you with endless travel, finer resolution, and durability. One trades simplicity for limits; the other trades complexity for freedom.

#stemantics #electronics #engineering #sensors #embeddedsystems

## Stats

- **Views:** 17,953
- **Likes:** 4,524
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- **Comments:** 15

## Tags

sensors, engineering, embeddedsystems, stemantics, electronics

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