The **47LAC-200B-R** is a specific model of an **Electromagnetic Passive Buzzer** (also referred to as a transducer). These components are widely used in consumer electronics, automotive alerts, and industrial equipment to provide audible feedback. Below is a detailed breakdown of its technical specifications and characteristics. --- ### 1. Key Technical Specifications | Parameter | Typical Value / Specification | | :--- | :--- | | **Type** | Electromagnetic / Passive | | **Operating Voltage** | 1.0V ~ 2.0V (Typical 1.5V) | | **Rated Current** | Max 10 - 30mA (depending on driving frequency) | | **Sound Pressure Level (SPL)** | ~80dB at 10cm | | **Resonant Frequency** | ~2000Hz - 2700Hz | | **Coil Resistance** | ~40Ω - 50Ω | | **Operating Temperature** | -20°C to +70°C | ### 2. Physical Construction The "47LAC" series typically features a compact, circular form factor designed for space-constrained PCB layouts. * **Housing:** Usually made of NORYL (a plastic blend) for heat resistance during soldering. * **Terminals:** Through-hole pins (DIP) or Surface Mount (SMD), depending on the specific suffix. * **Diaphragm:** A metal plate moved by the magnetic field generated by the internal coil. ### 3. Working Principle: Passive vs. Active It is crucial to note that this is a **Passive** buzzer. * **Passive (Transducer):** It does not have an internal oscillation circuit. To produce sound, you must provide a square wave signal (PWM) at its resonant frequency. * **Active (Indicator):** These only require a DC voltage to beep. The 47LAC-200B-R **cannot** beep if simply connected to a DC battery; it requires a toggling signal. ### 4. Circuit Integration Example To drive this buzzer using a microcontroller (like an Arduino or ESP32), a transistor is recommended because the current draw may exceed the GPIO pin limit. ```cpp // Example: Driving a passive buzzer via PWM int buzzerPin = 9; // Connect to Base of NPN transistor void setup() { pinMode(buzzerPin, OUTPUT); } void loop() { tone(buzzerPin, 2048); // Send 2048Hz square wave delay(500); noTone(buzzerPin); // Stop sound delay(500); } ``` --- ### 5. Common Applications * **Household Appliances:** Microwaves, washing machines, and air conditioners. * **Measurement Tools:** Multimeters or handheld scanners. * **Computing:** Motherboard POST codes (legacy beeps). ---