The **RPR-03-R** is an integrated reflective photosensor (optical sensor) manufactured by ROHM Semiconductor. It combines an infrared light-emitting diode (LED) and a high-sensitivity phototransistor in a single package. ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Type** | Reflective Photosensor | | **Light Source** | Infrared LED | | **Detector** | Phototransistor | | **Peak Wavelength** | 940 nm (Infrared) | | **Operating Voltage** | 1.3V (Forward Voltage typical) | | **Collector Current ($I_C$)** | Max 10mA - 30mA (varies by gain) | | **Detection Distance** | 0.5 mm to 3.0 mm (Optimal) | | **Package Size** | Small Surface Mount / Compact | --- ### 2. Internal Components and Functionality The device operates on the principle of **Optical Reflection**: 1. **The Emitter (LED):** Emits infrared light at a specific wavelength. 2. **The Detector (Phototransistor):** Remains in an "OFF" state when no light is reflected back. 3. **The Process:** When an object passes in front of the sensor, the IR light bounces off the object and hits the phototransistor. This causes the transistor to conduct current, signaling the presence or distance of an object. --- ### 3. Basic Circuit Diagram To use the RPR-03-R, you typically need two resistors: one for the LED current limiting and one for the output pull-up/down. ```text VCC (3.3V/5V) | +---+-------+ | | [R1] [R2] (Resistors) | | [Anode] [Collector] | | (LED) (Transistor) <-- RPR-03-R | | [Cathode] [Emitter] | | GND Output (To MCU) ``` --- ### 4. Common Applications * **Disc Detection:** Detecting the presence of CDs/DVDs in trays. * **Paper Sensing:** Used in printers and copiers to detect the edge of paper. * **Limit Switching:** Detecting the "Home" position in CNC or 3D printer axes. * **Object Counting:** Counting items on a high-speed assembly line. ### 5. Features and Benefits * **Built-in Filter:** Includes a visible light filter to reduce interference from ambient light. * **Compact Design:** Ideal for space-constrained electronics. * **High Sensitivity:** Capable of detecting objects with low reflectivity.