Rotary Encoder Frequently Asked Questions

This is an output circuit using a transistor, with the collector serving as the output terminal. When the transistor is ON, it outputs less than 0.5V, but when it is OFF, the signal level becomes uncertain.
To avoid this situation, the collector terminal is usually pulled up externally and converted into a voltage signal.

With open-collector outputs, the user needs to provide their own power supply, but the advantage is that the voltage level can be freely set.

Open collector output circuit

Recommended circuit (for reference)