Sharp Microelectronics GP2A25 Series Photointerrupter - Reflective Type, 3-7mm Range, TTL Output

The Sharp Microelectronics GP2A25 photointerrupter is designed for a standard 5V DC supply and provides a digital TTL output signal. The output pin switches between logic high and low states based on the presence or absence of a reflective target within its 3–7mm sensing window, making it directly compatible with microcontrollers like Arduino, Raspberry Pi, and industrial PLC digital inputs.

The sensor uses a modulated (pulsed) infrared LED. The detector circuit is tuned to this specific modulation frequency, which allows it to effectively filter out constant ambient light (e.g., sunlight, room lighting) and electrical noise. This results in highly reliable and stable object detection with minimal false triggering in varying environmental lighting conditions.

For reliable operation, mount the sensor so its front face is parallel to the target surface, maintaining a gap between 3mm and 7mm. Ensure the target surface is reflective (e.g., white paper, retro-reflective tape) for maximum signal strength. Avoid mounting where dust, dirt, or condensation could accumulate on the optical window, as this will attenuate the signal.

The GP2A25 relies on the reflection of infrared light. Transparent objects (like clear plastic or glass) may not reflect sufficient IR light to be detected reliably. Very dark or matte black objects absorb most IR light and will also provide a weak or non-existent reflection, potentially causing detection failures. It is best suited for detecting opaque, light-colored, or specifically reflective surfaces.