The **MEWT-13A-R** is a specific type of **Magnetic Buzzer** (also known as an electromagnetic transducer) commonly used in consumer electronics, automotive alerts, and industrial equipment. Below is a detailed breakdown of its electronic parts, specifications, and internal structure. --- ### 1. Key Technical Specifications The "13A" in the part number typically refers to its diameter (13mm), while the "R" often indicates it is a **RoHS compliant** or side-opening version depending on the specific manufacturer (like Star Micronics or similar vendors). | Parameter | Typical Value | | :--- | :--- | | **Type** | Magnetic / Electromagnetic Transducer | | **Operating Voltage** | 1.0V – 2.0V DC (Typical 1.5V) | | **Rated Current** | Max 10mA - 30mA | | **Sound Pressure Level (SPL)** | ~80dB at 10cm | | **Resonant Frequency** | 2,048 Hz (Standard for many 13mm models) | | **Coil Resistance** | 16 $\Omega$ – 42 $\Omega$ (Varies by sub-model) | | **Mounting Type** | Through-hole (Pins) | --- ### 2. Internal Electronic Components A magnetic buzzer like the MEWT-13A-R does not usually contain an internal driving circuit (it is a **transducer**, not an indicator). It requires an external oscillating signal to function. #### A. The Coil (Copper Winding) * **Function:** When an alternating current (AC) or pulsed DC passes through the coil, it creates a fluctuating magnetic field. * **Material:** Very fine enameled copper wire. #### B. The Permanent Magnet * **Function:** Provides a static magnetic bias. This ensures that the metal diaphragm is always under slight tension and reacts correctly to the fluctuations in the coil's field. #### C. The Metal Diaphragm (Disk) * **Function:** A thin plate of ferromagnetic material. It is pulled toward and pushed away from the coil/magnet assembly rapidly, vibrating the air to create sound waves. #### D. The Housing (Casing) * **Material:** Usually PPO (Polyphenylene Oxide) plastic. * **Sound Port:** A small hole (top or side) designed to act as an acoustic chamber to amplify the sound at the resonant frequency. --- ### 3. Application Circuitry Because the MEWT-13A-R is a transducer, you cannot simply connect it to a battery to get sound. You must use a switching component: 1. **Transistor Driver:** A NPN transistor (like a 2N2222) is used to switch the buzzer on and off at the desired frequency (e.g., 2kHz). 2. **Flyback Diode:** Because the buzzer is inductive (it contains a coil), a diode should be placed in parallel with it to protect the circuit from voltage spikes when the magnetic field collapses. --- ### 4. Comparison: Transducer vs. Indicator | Feature | MEWT-13A-R (Transducer) | Built-in Indicator | | :--- | :--- | :--- | | **Circuitry** | External oscillator required | Internal oscillator included | | **Flexibility** | Can play different tones/frequencies | One fixed tone | | **Complexity** | Higher (requires MCU programming) | Lower (Plug and play) |