Description
The SFM-27 Continuous Tone Electronic Buzzer is a high-output piezoelectric alarm device designed for industrial control panels, security systems, and DIY electronics projects. Built around the HYT-3015B piezo ceramic element, this active buzzer features a built-in oscillator circuit, meaning it produces a continuous, high-pitched tone simply by applying a DC voltage within its operating range — no external PWM signal, tone generator, or driver circuitry is required.
At the heart of the SFM-27 is a piezoelectric ceramic disc bonded to a metal plate. When an oscillating electrical field is applied, the ceramic material stretches and shrinks, causing the metal plate to bend and generate sound waves in the air . The integrated drive circuit handles the oscillation internally, so the buzzer activates immediately upon power-up. The continuous tone output is ideal for sustained alarm conditions, equipment status indication, and attention-grabbing alerts where a steady sound is preferred over an intermittent pattern.
The wide operating voltage range of DC 3V to 24V is a key advantage of this buzzer. It can operate from low-voltage battery packs, 5V USB rails, 12V automotive systems, or 24V industrial control circuits without any adjustment or external regulation . The sound pressure level reaches approximately 85dB to 95dB at 10cm, making it clearly audible in noisy environments such as factory floors, machine shops, and outdoor installations . Current consumption is low at approximately 12mA to 20mA, making it suitable for battery-powered and energy-conscious designs .
The buzzer features a compact cylindrical plastic housing measuring approximately 30mm × 15mm (diameter × height), with pre-attached wire leads for easy connection . The red wire connects to the positive terminal (+) and the black wire to the negative terminal (-) . The white housing provides a clean, professional appearance suitable for panel mounting. Mounting holes are provided for secure installation in equipment enclosures.
The SFM-27 is widely used in industrial control panels, security alarm systems, equipment fault indicators, timers and reminders, home automation, medical devices, automotive warning systems, and educational STEM projects. It is also a popular choice for Arduino and DIY projects where a simple, reliable audible indicator is required.
Important Note: The SFM-27 is an active buzzer — it produces a fixed continuous tone when powered and cannot play melodies or variable frequencies. For intermittent or variable tones, use a passive buzzer with PWM control. When driving directly from a microcontroller GPIO pin, note that the buzzer may draw up to 20mA, which is within the safe continuous current rating of most MCU pins (typically 20mA). For 24V operation, a transistor driver circuit is recommended. The buzzer is not waterproof — avoid exposure to moisture and corrosive environments.
Whether you are building an industrial alarm panel, a security system, or a DIY notification device, the SFM-27 Continuous Tone Electronic Buzzer provides a reliable, high-output solution for audible alerting. It is suitable for individual makers, engineers, and businesses purchasing in bulk for product development or industrial applications.
Features
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Active buzzer with built-in oscillator — Produces sound directly from DC voltage; no PWM required
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Wide voltage range — Operates from DC 3V to 24V; compatible with battery, 5V, 12V, and 24V systems
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Continuous tone output — Steady, high-pitched alarm suitable for sustained alert conditions
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High sound pressure — 85dB–95dB at 10cm for clear audibility in noisy environments
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Low current consumption — Approximately 12–20mA, suitable for battery-powered designs
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Compact 30×15mm package — Standard form factor for panel and equipment mounting
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Pre-attached wire leads — Red (+) and black (-) wires for simple connection
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Clear polarity marking — Red wire indicates positive terminal
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Wide application range — Industrial panels, security alarms, timers, home automation, automotive
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Cost-effective — Affordable solution for audible indication in volume production
Technical Specifications
| # | Parameter | Specification |
|---|---|---|
| 1 | Model | SFM-27 (HYT-3015B) |
| 2 | Buzzer Type | Piezoelectric Active Buzzer (built-in oscillator) |
| 3 | Operating Voltage | DC 3V – 24V |
| 4 | Rated Voltage | 12V DC |
| 5 | Resonant Frequency | 3100Hz ± 500Hz |
| 6 | Sound Pressure Level | 85dB – 95dB @ 10cm |
| 7 | Current Consumption | ~12–20mA (typical) |
| 8 | Package Size | Φ30mm × 15mm, wire length ~11cm |
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