9*3.2mm SMD Magnetic Passive Buzzer

Technical Specifications

Key Attributes

Expanded cavity for low‑frequency optimisation – 3.2 mm height provides increased internal resonance volume versus 2.5 mm counterparts, enhancing acoustic efficiency at 2.7 kHz without enlarging PCB footprint

Dual‑impedance unified platform – 16 Ω and 32 Ω options from identical 9.0 × 3.2 mm mechanical envelope, eliminating mechanical redesign when evaluating drive voltage architectures across product generations

Low‑frequency noise penetration – 2700 Hz resonant centre targets the 2–3 kHz band where industrial ambient noise spectral density is minimised, improving alert perceptibility in machinery and vehicle environments

Voltage‑optimised current efficiency – 16 Ω variant ≤100 mA at 3.6 V; 32 Ω variant ≤80 mA at 5 V; verify thermal and EMI performance in target enclosure

Extended cold‑weather storage – -40 °C storage rating supports arctic logistics, high‑altitude equipment, and winter‑stored machinery without parametric degradation

Reflow‑compatible LCP housing – black liquid crystal polymer withstands 255 ± 5 °C lead‑free reflow peaks with up to 3 passes, maintaining dimensional stability across full thermal range

Application Environments

Warehouse automation and logistics robotics – collision avoidance, pick‑completion, and charging‑dock alerts in AGVs, AMRs, and automated sortation systems operating in high‑echo industrial halls

Electric vehicle charging infrastructure – connection‑status, fault, and session‑complete tones in Level 2 wallboxes and DC fast‑charging pedestals with 5 V internal bus architectures

Telecommunications edge equipment – thermal‑threshold, fan‑failure, and power‑redundancy alarms in 5G small cells, remote radio units, and outdoor backhaul enclosures

Commercial kitchen and food‑service equipment – cycle‑complete, temperature‑reached, and door‑ajar alerts in convection ovens, blast chillers, and automated beverage dispensers

Rail and transit interior systems – door‑obstruction, next‑stop, and emergency‑intercom tones in commuter trains, subway cars, and tram platforms with 24 V‑to‑5 V regulated subsystems

Industrial pump and compressor controllers – cavitation, overpressure, and maintenance‑interval alerts in wastewater stations, HVAC chillers, and pneumatic distribution panels

Manufacturing & Reliability Assurance

MEIDI produces both MLT‑9032 variants on dedicated SMD assembly lines with automated coil winding, soldering, and acoustic calibration. Our Jiangsu facility maintains ISO 9001:2015 certification, with statistical process control applied at every production stage.

Each production batch undergoes uniform qualification testing:

Electrical characterisation – 100% verification of coil resistance, operating current, and resonant frequency

Acoustic validation – statistical sampling confirms SPL ≥ 80 dB; measured results consistently exceed 85 dB

Climatic endurance – 48‑hour high‑temperature storage at +80 °C, 48‑hour low‑temperature storage at -30 °C, and 5‑cycle thermal shock (-30 °C ↔ +80 °C, 30‑minute dwell per extreme)

Mechanical stress – sinusoidal vibration (10–55 Hz, 1.0 mm amplitude, XYZ axes, 0.5 hours total) and 75 cm free‑fall drop onto 10 mm hardwood (3 impacts)

Humidity resistance – 48 hours at 50 °C / 95% RH with 2‑hour recovery and electrical characterisation

Solder heat resistance – 250 °C for 10 seconds with 2.0 mm body‑to‑solder clearance, plus reflow profile compliance

RoHS and REACH conformity documentation is available. Lot identification codes provide full traceability to production date, test results, and raw material certificates.

Integration Q&A

Q1: How does the 3.2 mm MLT‑9032 compare to the 2.5 mm MLT‑9025 and 4.0 mm MLT‑8540?

The MLT‑9032's 3.2 mm height represents a middle path between the MLT‑9025 and MLT‑8540 families. Acoustic output is comparable across all three (≥80 dB), but the taller cavity provides more consistent off‑resonance response and reduced sensitivity to enclosure acoustic loading. Select the MLT‑9025 for ultra‑slim designs, the MLT‑9032 for balanced clearance, and the MLT‑8540 for maximum acoustic headroom where vertical space is available.

Q2: What drive circuit is recommended for each variant?

The 16 Ω variant at 3.6 V draws ≤100 mA and can be driven directly from capable MCU GPIO pins (verify pin current rating ≥100 mA) or through a simple NPN transistor switch with 180 Ω base resistor. The 32 Ω variant at 5 V draws ≤80 mA but requires a driver stage when driven from 3.3 V logic; from 5 V logic, a 330 Ω base resistor with general‑purpose transistor (h_FE ≥ 200) provides adequate drive. A flyback diode (1N4148 or similar) across the coil is mandatory for both variants to protect the driving element from inductive kickback during switching.

Q3: Can the MLT‑9032 replace through‑hole magnetic buzzers in existing designs?

Yes, with PCB layout revision from through‑hole to SMD pads. The 9.0 mm circular footprint occupies less board area than typical 12 mm through‑hole buzzers while eliminating drilled holes and manual insertion. Acoustic output (≥80 dB) meets or exceeds many 12 mm through‑hole equivalents. The primary design consideration is drive circuit migration: through‑hole buzzers often operate at 12 V with internal oscillators, while the MLT‑9032 requires external 2.7 kHz excitation at 3.6 V or 5 V. A microcontroller PWM output or simple oscillator replaces the self‑oscillating drive.

Q4: Is the 3.2 mm height compatible with standard smartphone and tablet enclosures?

The 3.2 mm profile exceeds the z‑axis budget of most modern smartphones (typically 2.0–2.5 mm above PCB) but fits comfortably in tablet, laptop, industrial handheld, and automotive interior enclosures where 4.0–6.0 mm clearance is common. For ultra‑thin consumer electronics, the MLT‑9025 (2.5 mm) or MLT‑5020 (2.0 mm) families are more appropriate. The MLT‑9032 targets applications where acoustic performance outweighs absolute slimness.

Q5: Are custom resonant frequencies or impedance values available for OEM programs?

Yes. MEIDI supports OEM/ODM customisation including intermediate impedance values, modified resonant frequencies (2.0–3.5 kHz range), alternative housing colours for visual identification, and custom tape‑and‑reel packaging. Minimum order quantities and lead times apply. Contact our sales team to discuss specific requirements and request a quotation for custom configurations.

Q6: What is the typical acoustic lifetime under continuous operation?

The standard qualification includes 96 hours of continuous operation at 25 °C with a 50% duty‑cycle square wave. For indefinite continuous‑tone applications, MEIDI recommends limiting duty cycle to 50% or implementing intermittent alert patterns (e.g., 1 second on, 3 seconds off) to reduce coil heating and extend service life. Extended lifetime test data for specific operating conditions is available upon request.