The **MH18TDD-R** is an electronic component primarily classified as a **Hall Effect Sensor**. These sensors are used to detect the presence and strength of a magnetic field and convert that information into electrical signals. Below is a detailed breakdown of its electronic characteristics and specifications. --- ## 1. Core Functionality The MH18TDD-R is a **Unipolar Hall Effect Switch**. Unlike bipolar sensors (which require both North and South poles to toggle), a unipolar sensor activates in the presence of a specific magnetic pole (usually South) and deactivates when that pole is removed. ### Key Electronic Attributes: * **Sensor Type:** Hall Effect Integrated Circuit (IC). * **Output Type:** Open-Drain (requires a pull-up resistor). * **Switching Logic:** Digital (High/Low). --- ## 2. Technical Specifications The following table outlines the typical electrical parameters for the MH18 series: | Parameter | Typical Value | Unit | | :--- | :--- | :--- | | **Supply Voltage ($V_{CC}$)** | 2.5 to 24 | Volts (V) | | **Output Current ($I_{OUT}$)** | 25 - 50 | Milliamps (mA) | | **Operating Temperature** | -40 to +125 | Celsius (°C) | | **Magnetic Operate Point ($B_{OP}$)** | 30 - 60 | Gauss (G) | | **Magnetic Release Point ($B_{RP}$)** | 10 - 45 | Gauss (G) | | **Package Type** | SOT-23 or TO-92S | - | --- ## 3. Pin Configuration For the common **SOT-23** surface-mount package, the pinout is generally as follows: | Pin Number | Name | Description | | :--- | :--- | :--- | | 1 | **$V_{CC}$** | Input Power Supply | | 2 | **OUT** | Output Signal (Open Drain) | | 3 | **GND** | Ground | --- ## 4. Typical Application Circuit Because the output is **Open-Drain**, you must connect a pull-up resistor from the Output pin to $V_{CC}$ to get a valid digital signal. ```python # Conceptual Wiring Schematic # [VCC] ----+---------- [Pin 1: VCC] # | # [Resistor 10k] # | # [MCU IN]--+---------- [Pin 2: OUT] # # [GND] --------------- [Pin 3: GND] ``` --- ## 5. Common Use Cases 1. **Proximity Sensing:** Detecting when a door or lid is closed. 2. **Speed Measurement:** Counting rotations of a wheel with an embedded magnet (Tachometer). 3. **Non-contact Switching:** Replacing mechanical switches to prevent wear and tear in harsh environments. 4. **Liquid Level Sensing:** Detecting a magnetic float in a tank.