The **ASP-2121-R** is a high-performance, precision acoustic component, specifically a **Surface Mount (SMT) Magnetic Buzzer/Transducer** manufactured by companies like Mallory Sonalert Products. It is designed for compact electronic devices requiring audible alerts. --- ### 1. Key Technical Specifications | Parameter | Specification | | :--- | :--- | | **Technology** | Magnetic Transducer (External Drive) | | **Rated Voltage** | 1.5 Vp-p (Peak-to-Peak) | | **Operating Voltage** | 1.0 - 2.0 Vp-p | | **Rated Current** | Max 80 mA | | **Sound Pressure Level (SPL)** | ≥ 85 dB @ 10cm | | **Resonant Frequency** | 2,730 Hz | | **Operating Temperature** | -30°C to +70°C | | **Mounting Type** | Surface Mount (SMT) | --- ### 2. Internal Electronic Structure Unlike "indicators" that beep as soon as DC power is applied, the ASP-2121-R is a **transducer**. * **Coil and Magnet:** It consists of a copper wire coil wrapped around a core and a permanent magnet. * **Diaphragm:** A metal disk (diaphragm) is suspended above the coil. * **Function:** When an oscillating signal (square wave) is passed through the coil, it creates a fluctuating magnetic field. This field pulls and releases the diaphragm at the frequency of the input signal, creating sound waves. ### 3. Driving Circuit Requirements To operate this part, you cannot simply connect it to a battery. You must provide a square wave at its resonant frequency (2,730 Hz). Below is a typical driving configuration using an NPN transistor: ```cpp // Example: Arduino pseudocode to drive the ASP-2121-R void setup() { pinMode(9, OUTPUT); // Connect to base of NPN transistor } void loop() { tone(9, 2730); // Generate the 2.7kHz square wave delay(500); // Beep for 500ms noTone(9); // Silence delay(500); } ``` --- ### 4. Physical Characteristics * **Dimensions:** It features a very small footprint (approx. 12mm x 12mm x 8.5mm), making it ideal for portable electronics. * **Housing:** Usually made of LCP (Liquid Crystal Polymer) plastic to withstand the high temperatures of lead-free reflow soldering. * **Polarity:** It is a polarized component; the top of the casing is usually marked with a "+" to indicate the positive terminal. --- ### 5. Common Applications * **Medical Instrumentation:** Heart rate monitors or glucose meters. * **Handheld Devices:** Scanners and mobile POS terminals. * **Consumer Electronics:** Microwave timers, alarm clocks, or white goods. * **Automotive:** Dashboard alerts or proximity sensor feedback.