What Is a Rotary Switch / Encoder?
A rotary encoder is an input component that converts a knob's rotation and direction into digital pulses. Unlike a rotary switch, most encoders rotate without limit.
Rotary Switch vs Encoder
A rotary switch seats at defined positions (detents) and each position corresponds to a fixed contact. An encoder, instead of an absolute position, produces the rotation direction and step; it can be turned without limit.
Quadrature Signal
An incremental encoder produces two outputs: A and B. By looking at the phase difference of these two signals, the direction (clockwise/counterclockwise) and the amount of rotation are determined. This is called quadrature encoding.
| Type | Property |
|---|---|
| Rotary switch | Fixed detent/position |
| Incremental encoder | A/B pulses, unlimited rotation |
| Absolute encoder | A unique code for each angle |
Button Feature
Many encoder knobs can also be pressed (push); this is used as a "select/confirm" input. So value adjustment and confirmation are both obtained with a single component.
Where Is It Used?
Volume/menu knobs, 3D-printer interfaces, measurement instruments, motor position feedback and MCU-based control panels.
Common Mistakes
- No debounce: if the A/B signals bounce, the count skips/reverses.
- Assuming it's absolute: an incremental encoder forgets its position when power is lost.
- Fast rotation: insufficient read speed misses steps.
Frequently Asked Questions
Is an encoder a potentiometer?+
How is direction found?+
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