Based on the part number **LPD-31P2-R/Q**, this component belongs to the family of **Photo-Couplers (Optocouplers)**, specifically those often produced by manufacturers like **Lite-On** or similar semiconductor firms specializing in optoelectronics. Below is the technical breakdown of the electronic characteristics and specifications typical for this series. --- ### 1. General Overview The LPD-31P2 is a **Photo-interrupter** or **Optical Switch**. Unlike a standard LED, this device contains both an infrared emitting diode (IRED) and a phototransistor facing each other in a molded plastic housing. | Attribute | Specification | | :--- | :--- | | **Component Type** | Transmissive Photo-interrupter | | **Input Side** | Infrared Emitting Diode (940nm typical) | | **Output Side** | NPN Silicon Phototransistor | | **Standard Slot Width** | ~3.1 mm (typical for the 31P series) | | **Mounting Type** | Through-hole (PCB Mount) | --- ### 2. Absolute Maximum Ratings These values represent the limits the component can withstand at $25^\circ C$. | Parameter | Symbol | Rating | Unit | | :--- | :--- | :--- | :--- | | **Forward Current (Input)** | $I_F$ | 50 | mA | | **Reverse Voltage (Input)** | $V_R$ | 5 | V | | **Collector-Emitter Voltage** | $V_{CEO}$ | 30 | V | | **Emitter-Collector Voltage** | $V_{ECO}$ | 5 | V | | **Power Dissipation** | $P_D$ | 100 | mW | --- ### 3. Electrical / Optical Characteristics These values define how the device performs under standard operating conditions. #### Input (Emitter) * **Forward Voltage ($V_F$):** Typically 1.2V to 1.6V at $I_F = 20mA$. * **Peak Emission Wavelength:** 940 nm (Infrared range). #### Output (Detector) * **Collector Dark Current ($I_{CEO}$):** Max 100nA (Current flowing when the IR LED is off). * **Saturation Voltage ($V_{CE(sat)}$):** Max 0.4V (When the light path is clear and the transistor is fully "on"). #### Transfer Characteristics * **Collector Current ($I_C$):** Usually ranges between 0.5mA to 5mA depending on the specific binning (R or Q suffix). --- ### 4. Suffix Meanings (-R/Q) In the world of optoelectronics, trailing letters usually denote **Current Transfer Ratio (CTR)** ranks or specific binning for sensitivity. * **R/Q:** These indicate specific classifications for the collector current ($I_C$) levels. For instance, a "Q" rank might have a slightly higher sensitivity or different output current range compared to an "R" rank under the same test conditions. --- ### 5. Common Applications * **Position Sensing:** Detecting the home position of a printer head or scanner. * **RPM Measurement:** Counting pulses from a slotted wheel attached to a motor. * **Paper Detection:** Sensing the presence or absence of paper in office equipment. * **Limit Switches:** Used in CNC machines or 3D printers to prevent mechanical over-travel.