The **PK-24-R** is a high-performance piezoelectric buzzer/transducer widely used in industrial, automotive, and consumer electronics. It is manufactured by various companies, most notably **Mallory Sonalert** and **Pro-Signal**. Below is a detailed breakdown of its electronic specifications and characteristics. --- ### 1. General Specifications The PK-24-R is an **internally driven** (constant tone) indicator, meaning it has an integrated circuit that generates the sound frequency when DC voltage is applied. | Parameter | Value/Specification | | :--- | :--- | | **Type** | Piezoelectric Indicator (Active) | | **Operating Voltage** | 3V DC to 15V DC | | **Rated Voltage** | 12V DC | | **Current Consumption** | ≤ 12mA at 12V DC | | **Sound Pressure Level (SPL)** | ≥ 90 dB (at 10cm/12V DC) | | **Resonant Frequency** | 3,300 Hz ± 500 Hz | | **Tone Type** | Continuous | | **Mounting Type** | Panel Mount (Nut & Washer) | --- ### 2. Physical Construction The "R" suffix often denotes specific lead configurations or RoHS compliance depending on the manufacturer. * **Housing Material:** Typically ABS or PBT plastic (Black). * **Connection:** Usually features 28 AWG wire leads (Red for Positive, Black for Negative). * **Dimensions:** * Diameter: ~24mm * Height: ~15mm * **Installation:** It features a threaded body with a plastic nut for easy mounting through a 20-22mm hole. --- ### 3. Electronic Characteristics #### A. High Efficiency Because it utilizes the piezoelectric effect (mechanical stress generated by an electric field on a ceramic disk), it consumes significantly less power than electromagnetic buzzers. #### B. Internal Drive Circuit Unlike "transducers" which require an external square wave frequency to make sound, the PK-24-R is an "indicator." * **Application:** Simply connect it to a battery or a microcontroller pin (via a transistor). * **Polarity:** It is polarity-sensitive. Reversing the leads will prevent it from functioning and may damage the internal oscillator. #### C. Typical Circuit Diagram To control a PK-24-R with a microcontroller (like an Arduino/ESP32), use the following configuration to protect the MCU pin from current spikes: ``` [MCU PIN] --- [1kΩ Resistor] --- [Base of NPN Transistor (2N2222)] | [+12V DC] ---------- [PK-24-R Red Lead] | [PK-24-R Black Lead] - [Collector of NPN] | [GND] ---------------- [Emitter of NPN] ``` --- ### 4. Common Applications * **Alarms:** Smoke detectors, security systems, and CO2 monitors. * **Industrial:** Control panel alerts and timer notifications. * **Automotive:** Reverse sensors or seatbelt reminders. * **Medical:** Patient monitoring equipment alerts.