The **AAC-AD112-R** is a high-performance, ultra-miniature **Surface Mount Device (SMD) Piezoelectric Transducer** (Buzzer) manufactured by AAC Technologies. It is widely used in compact consumer electronics for audible feedback. --- ## 1. Technical Specifications The following table summarizes the key electrical and physical characteristics: | Parameter | Specification | | :--- | :--- | | **Type** | Piezoelectric Transducer (External Drive) | | **Rated Voltage** | 3.0 Vp-p (Square Wave) | | **Operating Voltage** | 1.0 ~ 25.0 Vp-p | | **Current Consumption** | Max 3mA at Rated Voltage | | **Sound Pressure Level (SPL)** | Min 75dB at 10cm / 3.0 Vp-p / 4.0kHz | | **Resonant Frequency** | 4,000 Hz (±500 Hz) | | **Capacitance** | 12,000 pF ± 30% at 120Hz | | **Operating Temperature** | -20°C to +70°C | | **Dimensions** | 12.0 x 12.0 x 3.0 mm | --- ## 2. Key Electronic Components & Working Principle The AAC-AD112-R operates differently than a standard electromagnetic speaker. Its internal structure consists of: ### A. Piezoelectric Ceramic Element The core component is a thin disc of piezoelectric ceramic bonded to a metal diaphragm (usually brass or stainless steel). * **Piezo Effect:** When an alternating voltage is applied, the ceramic expands and contracts, causing the metal diaphragm to bend and vibrate. * **Frequency Dependence:** This part is an **External Drive** type, meaning it does not have internal oscillation circuitry. You must provide a square wave at its resonant frequency (4kHz) to produce sound. ### B. Drive Circuitry (External Requirement) Because it behaves like a capacitor, it requires a specific driver circuit. A common way to drive it is using a transistor or a dedicated piezo driver IC. ```cpp // Example: Basic Arduino pseudo-code to drive the AAC-AD112-R int buzzerPin = 9; void setup() { pinMode(buzzerPin, OUTPUT); } void loop() { tone(buzzerPin, 4000); // Send a 4kHz square wave delay(500); noTone(buzzerPin); delay(500); } ``` --- ## 3. Physical Features & Mounting * **SMD Package:** The "R" in the part number typically refers to Tape & Reel packaging for automated SMT (Surface Mount Technology) assembly. * **Sound Port:** It features a top-opening or side-opening hole for sound emission. * **Polarity:** While piezo elements are generally non-polar, the footprint often specifies a positive terminal for consistent phase performance in multi-speaker arrays. --- ## 4. Common Applications * **Mobile Devices:** Haptic/audio feedback in smartphones or tablets. * **Household Appliances:** Beepers for microwave ovens, washing machines, and timers. * **Medical Equipment:** Alarm signals for portable monitors. * **Industrial:** Status indicators on handheld scanners.