The **48-SM-R** is a specific surface-mount (SMD) part number commonly associated with **Electromagnetic Buzzers** or **Magnetic Transducers**. These components are widely used in consumer electronics, medical devices, and automotive systems to provide audible feedback. --- ### 1. Technical Specifications Below are the typical technical parameters for a 48-SM-R series magnetic buzzer: | Parameter | Specification (Typical) | | :--- | :--- | | **Type** | Magnetic / Electromagnetic | | **Mounting Type** | Surface Mount (SMD) | | **Rated Voltage** | 3.0V - 5.0V DC | | **Operating Voltage** | 2.0V ~ 6.0V DC | | **Current Consumption** | Max 80 - 100 mA | | **Sound Pressure Level (SPL)** | Min 85 dB @ 10cm | | **Resonant Frequency** | 2400 Hz - 2700 Hz | | **Operating Temperature** | -40°C to +85°C | --- ### 2. Physical Characteristics The "48" in the part number often refers to the physical size of the casing (e.g., approximately 8.5mm x 8.5mm or similar compact footprints). * **Housing Material:** LCP (Liquid Crystal Polymer) or high-temperature plastic to withstand reflow soldering. * **Polarity:** Usually marked with a "+" or a chamfered corner to indicate the positive terminal. * **Acoustic Hole:** Located on the top or side to allow sound waves to exit. --- ### 3. Functional Mechanism The 48-SM-R is an **externally driven** transducer. Unlike an "indicator" which beeps as soon as DC power is applied, this part requires an external oscillating signal (PWM) to function. 1. **Coil:** A copper wire coil inside the housing. 2. **Magnet:** A permanent magnet creates a static field. 3. **Diaphragm:** A metal disk that vibrates. 4. **Process:** When an AC/PWM signal passes through the coil, it creates a fluctuating magnetic field that moves the diaphragm, producing sound at the frequency of the input signal. --- ### 4. Circuit Integration Example To drive a 48-SM-R from a microcontroller (like an Arduino or STM32), a transistor switching circuit is required because the current draw (up to 100mA) is too high for a standard GPIO pin. ```cpp // Example: Driving the 48-SM-R using a PWM Signal int buzzerPin = 9; // Connect to Base of NPN Transistor void setup() { pinMode(buzzerPin, OUTPUT); } void loop() { tone(buzzerPin, 2700); // Send 2.7kHz signal delay(500); // Beep for 0.5 seconds noTone(buzzerPin); // Stop delay(500); } ``` ---