1) What is an encoder?

An encoder converts mechanical motion into an electrical signal that represents position, speed, or direction. It is the most common feedback device used in motion systems.

2) Why feedback matters

Without feedback, systems assume motion occurred as commanded. With feedback, systems verify motion and correct errors.

• Detect missed steps
• Maintain accuracy under load
• Enable closed-loop control
• Improve safety and reliability

3) Encoder types overview

4) Incremental encoders

Incremental encoders output pulses as the shaft rotates. Position is determined by counting pulses.

• Channels A and B (quadrature)
• Direction from phase difference
• Index pulse (Z) for reference

5) Absolute encoders

Absolute encoders output a unique value for each position. The position is known immediately on power-up.

• Single-turn or multi-turn
• Parallel or serial output
• No homing required

6) Rotary vs linear encoders

7) Resolution, CPR & accuracy

Encoder resolution is often expressed as CPR (Counts Per Revolution).

8) Encoder signals & interfaces

• Quadrature (A/B): Incremental encoders
• Index (Z): Reference point
• SPI / I²C: Digital absolute encoders
• Analog: Sine/cosine outputs

9) Noise, shielding & wiring

Encoder signals are often low-level and susceptible to noise.

• Use twisted pairs for A/B signals
• Shield cables where possible
• Common ground reference
• Keep away from motor power wiring

10) Reading encoders with microcontrollers

Encoders can be read using:

• Interrupts (low speed)
• Hardware quadrature decoders
• Timer/counter peripherals

11) Encoder selection guide

12) Common problems & debugging

1. Missed counts due to noise
2. Incorrect CPR assumptions
3. Poor mechanical coupling
4. Floating grounds
5. Over-speeding the MCU input