SFM-27 Electronic Buzzer Alarm — 90dB, DC 3V to 24V
The SFM-27 is a self-contained piezo buzzer with a built-in oscillator, producing a continuous 2300Hz tone at 90dB from any DC supply between 3V and 24V. Unlike passive buzzers that require a PWM signal, the SFM-27 activates with a simple HIGH output from a GPIO pin through a transistor, or directly from a relay contact. The weatherproof ABS housing seals the buzzer for outdoor mounting.
- 90dB at 1 metre
- 3V–24V DC supply — covers 3.3V, 5V, and 12V systems
- 2300Hz self-oscillating tone — no PWM signal needed
- Weatherproof ABS housing — suitable for outdoor mounting
- Continuous tone — activate/deactivate via transistor or relay
| Specification | Value |
|---|---|
| Sound pressure | 90dB at 10cm |
| Frequency | 2300Hz |
| Supply voltage | 3V – 24V DC |
| Current draw | 30mA at 5V |
| Housing | ABS, sealed |
Can you connect the SFM-27 directly to an Arduino pin?
Not directly — the SFM-27 draws up to 30mA at 5V, more than the Arduino’s 40mA pin limit, and increases to higher current at 12V or 24V. Drive it through an NPN transistor (2N2222, BC547) with a 1k base resistor from the Arduino GPIO pin. The transistor switches the buzzer’s supply current independently of the Arduino pin.
Best for
Alarm systems, access control alerts, machine fault indicators, timer buzzers, security perimeter alarms, Arduino-triggered alerts, and any application needing a loud, reliable continuous tone from a compact weatherproof housing.
Why Kunkune
Shipped from UK stock. 60-day returns, no minimum order. Fast Royal Mail delivery.
Buying in bulk? For orders of 10+ units, contact us for trade pricing.
