The **LTHZ-112-R/T** is a high-performance, ultra-compact optical sensor module, commonly referred to as a **Reflective Type Phototransistor** or **Reflective Object Sensor**. It is designed for short-range detection, typically used in printers, scanners, and automated office equipment. --- ### 1. Key Internal Components The device integrates two primary electronic parts into a single miniature housing: | Part Name | Component Type | Function | | :--- | :--- | :--- | | **Emitter** | Infrared (IR) LED | Emits infrared light at a specific wavelength (typically 940nm). | | **Detector** | NPN Phototransistor | Detects the IR light reflected back from a surface or object. | | **Housing** | Black Plastic Case | Blocks ambient visible light to prevent interference and houses the optical lens. | --- ### 2. Technical Specifications The electrical characteristics are critical for circuit design. Below are the typical parameters for this class of device: | Parameter | Characteristic | Typical Value | | :--- | :--- | :--- | | **Forward Current ($I_F$)** | Emitter (LED) | 20mA - 50mA | | **Collector Current ($I_C$)** | Detector | 0.5mA - 2.0mA (Sensing dependent) | | **Peak Wavelength** | Spectral Output | 940 nm | | **Sensing Distance** | Focal range | 1mm to 5mm | | **Collector-Emitter Voltage** | Maximum ($V_{CEO}$) | 30V | --- ### 3. Working Principle The LTHZ-112-R/T operates on the principle of **Retroreflection**: 1. **Emission:** The internal IR LED sends out a beam of light. 2. **Reflection:** When an object (like paper or a mechanical gear) passes in front of the sensor, the light bounces back. 3. **Detection:** The Phototransistor receives the reflected light and becomes conductive, allowing current to flow from the Collector to the Emitter. 4. **Signal:** This current flow is converted into a voltage signal (usually via a pull-up resistor) that a Microcontroller (MCU) can interpret as a "High" or "Low" state. --- ### 4. Basic Circuit Connection To use the LTHZ-112-R/T, you must provide current limiting for the LED and a load resistor for the phototransistor. ```cpp // Schematic Logic: // [VCC] -- [Resistor 220ohm] -- [Anode | LED | Cathode] -- [GND] // [VCC] -- [Resistor 10kohm] -- [Collector | Phototransistor | Emitter] -- [GND] // | // +--- [Output Signal to MCU] ``` --- ### 5. Common Applications * **Paper Sensing:** Detecting the presence or edge of paper in printers. * **Encoders:** Counting pulses from a reflective disk to determine motor speed. * **Proximity Sensing:** Detecting the opening or closing of a device lid/cover. * **Industrial Automation:** Sorting small parts on a conveyor belt.