The Elecrow Crowtail – Photo Electric Counter 2.0 is a digital optical counting module that detects interruptions of a light beam using a groove IR optocoupler. Its design features a U‑shaped slot, with an IR emitter on one side and an IR receiver on the other. When an object passes through the slot, interrupting the IR beam, the sensor outputs a digital signal that can be used to count rotations, detect object passage, or measure speed. This makes it useful for tasks like counting conveyor belt items, measuring RPM with a disc having holes, or triggering alarms or events when beam interruption happens. The output is processed via an LM393 comparator so that the signal is clean and easy to read: when nothing is between the IR emitter and receiver, the output (logic signal D0) is LOW and an indicator LED is ON; when the beam is blocked (object in slot), the output goes HIGH and the LED turns OFF. A potentiometer is provided to adjust sensitivity, which helps in fine‑tuning detection (especially with variations in object color, ambient light, or IR source/receiver degradation). Powered from 3.3V to 5V via the Crowtail interface, the module is compact and easy to integrate into existing Crowtail‑compatible systems (like Crowduino or Arduino with Crowtail shield). Its small size and simple digital output make it well suited for both educational projects and practical sensing applications in robotics, automation, or DIY devices.