Rotary Encoders

Choose the right rotary encoder type before comparing specs

Incremental encoders do not retain position after power-off; absolute encoders do. For deeper background on the difference between encoder outputs and how quadrature works, that article helps once you have narrowed the family.

Quick comparison: module, bare encoder, optical shaft encoder, Hall motor encoder, and absolute magnetic sensor

For shaft-feedback options in an ESP32 project, the 3.3 V logic side and hardware counting support on ESP32 boards can matter as much as encoder resolution. For deeper implementation detail on optical models, see reading a photoelectric shaft encoder with a microcontroller.

Electrical compatibility checks that prevent the most common wrong encoder purchases

• CLK = channel A, DT = channel B, and SW = push button. On a typical hand-input encoder, A/B use two digital inputs, and SW is optional if you want click-to-select behavior.
• KY-040 rotary encoder with push switch includes onboard 10 kΩ pull-ups, which makes it the easier first-project choice than a bare encoder.
• EC11 rotary encoder with push button does not include pull-ups; most builds use the microcontroller’s internal pull-up resistors.
• Open-collector optical encoders such as the HN3806 class require pull-ups.
• On the 100PPR HN3806, the data lines must connect to VCC through 1 to 100 kΩ resistors, and the AB outputs should not be tied directly to VCC.
• The 360PPR HN3806 optical encoder also needs external pull-up resistors on both phases because its outputs are NPN open collector.
• ESP32 GPIOs are 3.3 V, so power a KY-040 from 3.3 V or level-shift any 5 V signals before feeding them into an ESP32 input.
• One interrupt pin per encoder is enough for x2 decoding; two pins allow x4 decoding. For higher pulse rates, ESP32 hardware PCNT and the timer encoder mode on STM boards reduce missed counts.
• AS5600 uses I2C instead of A/B quadrature decoding and sits at fixed address 0x36, which saves pulse-counting pins but matters if you want more than one on the same bus.

For a concrete hookup example, see wiring CLK, DT, and SW on a rotary encoder module.

Resolution, feel, and speed: how many pulses are actually enough?

For a hand-turned encoder knob, 15 to 30 detents per revolution is the normal range. That is why the KY-040 at 20 pulses per revolution feels right for menus rather than coarse or under-specced. The FZ0535 rotary encoder with reset button is also specified at 20 pulse precision, but adds a dedicated reset button when you want a quick return-to-zero control.

Motor feedback is a different sizing problem. The HN3806 options here are 100 PPR and 360 PPR, while the Hall motor encoder for JGB37 and JGA25 motors comes in 12, 13, or 16 CPR versions for lower-resolution integrated feedback. AS5600 uses absolute 12-bit angle measurement instead of pulse counting, which means 4096 positions per turn.

Watch the PPR/CPR distinction. In x4 quadrature decoding, CPR can equal 4 × PPR. That matters quickly at speed—a 400 PPR encoder at 3000 RPM generates 20,000 pulses per second—so more resolution is not always the right call, especially if your controller is not using hardware counting on ESP32. If you want the count-mode detail, see why one encoder can produce multiple counts per click.

Common mistakes to avoid before you order an encoder

• KY-040 is a module, while EC11 is the bare component used in this style of build. If you expect headers and plug-in wiring, choose the module.
• Mechanical knob encoders are for hand-turn speeds. For high-RPM motor feedback, move to an optical HN3806 or the Hall motor encoder instead of using a KY-040 or EC11.
• Incremental encoders lose position at power-off. If the system must know its angle immediately after reboot, use AS5600, not a standard incremental rotary encoder.
• AS5600 needs a diametrically magnetized magnet centered over the chip with a 0.5–3 mm air gap, and ferrous shafts or mounts should be avoided. The module includes a small magnet, but the mounting requirement still decides whether it will read cleanly.
• AS5600 uses fixed I2C address 0x36, so multiple sensors need bus planning such as a TCA9548A multiplexer or a second I2C bus.
• HC-020K is the right buy when you only need RPM. If you need direction too, choose a 2-channel quadrature encoder instead.
• The 16-position rotary DIP switch gives fixed 0-F positions, not continuous pulse output.
• A module does not solve debounce by itself. The resistors you see on a KY-040 are pull-ups, not a full debounce circuit, so software filtering is still the normal fix for skips or double counts.
• In a menu-driven interface, many buyers pair a hand encoder with LCD modules; blocking display updates can still make mechanical encoder decoding feel worse.

For the common symptom side of this problem, see why mechanical encoder modules can skip or double count without proper decoding.

FAQs on Rotary Encoders

Glossary

Incremental encoder

An incremental encoder reports movement step by step, but it does not remember position after power loss.

Absolute encoder

An absolute encoder reports the actual shaft angle at startup, which is why it suits power-loss-sensitive position sensing.

PPR

PPR means pulses per revolution on one channel, and it is the main resolution figure on shaft encoders.

CPR

CPR means counts per revolution, and with x4 quadrature decoding it can equal 4 × PPR.

Detent

A detent is the tactile click you feel when turning a hand encoder, and it strongly affects menu-control feel.

Pull-up resistor

A pull-up resistor holds a signal line high until the encoder pulls it low, which is required for bare EC11 parts and open-collector optical encoders.

Debounce

Debounce is the filtering that removes false transitions from mechanical contacts so the encoder does not skip or double count.

Open collector (NPN)

Open collector means the output can pull low but not drive high by itself, so products such as HN3806 optical encoders need pull-up resistors.