FC-33 Optocoupler Counter Module with LM393

The FC-33 is an optocoupler counter module built around the LM393 comparator and an infrared slot sensor. It detects the presence of objects passing through a 10mm wide slot, where an infrared LED on one side and a phototransistor on the other generate a digital pulse each time the light beam is interrupted. The module outputs a clean TTL-level digital signal (0 or 1) that can be connected directly to microcontrollers such as Arduino, making it suitable for motor speed measurement, object counting on production lines, and position limit control. It operates on a 5V DC supply (with a working range of approximately 3.2V to 5V), includes an output status indicator LED, and features a compact 28 × 20 × 16 mm board. Because the FC-33 optocoupler design minimizes interference from ambient light, it provides stable and repeatable pulse counting for robotics, educational, and industrial projects. This optical counter module is a practical solution for applications requiring reliable LM393 speed sensor-based detection and pulse counting.