The **MEWT-122W-R** is a specific model within the **MEWT series** of electromagnetic buzzers (transducers). These components are widely used in automotive, medical, and industrial electronics to provide audible feedback. Below is an explanation of its electronic characteristics and specifications. ### 1. Device Overview The MEWT-122W-R is a **washable, electromagnetic transducer**. Unlike a "piezo" buzzer, an electromagnetic transducer uses an electromagnet and a metal diaphragm to produce sound. | Feature | Specification | | :--- | :--- | | **Type** | Electromagnetic Transducer | | **Drive Type** | External Drive (Requires an oscillator circuit) | | **Washable** | Yes (Contains a protective tape for PCB cleaning) | | **Mounting Type** | Through-hole (Pins) | | **Orientation** | Top sound port | --- ### 2. Key Electrical Characteristics To operate this part effectively, you must understand its input requirements. It does not make sound just by applying DC voltage; it requires a **square wave signal**. | Parameter | Typical Value | | :--- | :--- | | **Rated Voltage** | 12.0 Vp-p | | **Operating Voltage** | 8.0 ~ 16.0 Vp-p | | **Rated Current** | Max 40 mA | | **Coil Resistance** | 140 $\pm$ 14 $\Omega$ | | **Sound Pressure Level (SPL)** | Min 85 dB (at 10cm) | | **Resonant Frequency** | 2,400 Hz | --- ### 3. Electronic Driving Circuit Since the MEWT-122W-R is a **transducer** (not an indicator), it lacks internal circuitry. You must provide a signal at its resonant frequency (2,400 Hz) to achieve maximum volume. #### Basic Schematic Logic: To drive this with a microcontroller (like an Arduino or ESP32), use a transistor switching circuit: ```cpp // Example Arduino Code snippet to drive MEWT-122W-R int buzzerPin = 9; // Connected to the base of a transistor void setup() { pinMode(buzzerPin, OUTPUT); } void loop() { // Generate a 2400Hz square wave tone(buzzerPin, 2400); delay(500); noTone(buzzerPin); delay(500); } ``` --- ### 4. Component Construction * **Magnet/Coil:** When current flows through the internal coil, it creates a magnetic field that moves a metal disk. * **Housing:** Typically made of PPO (Polyphenylene Oxide) plastic to withstand high soldering temperatures. * **Washable Tab:** The "W" in the part number usually signifies a waterproof adhesive tab over the sound hole. This allows the PCB to be washed after soldering without damaging the internals. **Note:** This tab must be removed after washing to allow sound to escape. ---