Signswise Incremental Optical Rotary Encoder for Arduino 600P/R Wide Voltage Power Supply DC 5-24V 6mm Shaft Quadrature

Works well

No issues so far. Good price.

I used the example code in the questions/answers section of this page, and the arduino was missing pulses. Sometimes the counts would sporadically go backwards. Slow revolutions would give hundreds of counts per revolution, but fast revolutions would give 30 counts.

I am using this with an arduino DIY preamp as a volume control (of all things).

Great item.