{"product_id":"sfm-20b-85db-active-buzzer-alarm-dc3-24v-continuous-arduino-industrial","title":"SFM-20B 85dB Active Buzzer Alarm — DC 3–24V, Continuous Sound, Arduino Industrial","description":"\u003ch2\u003eSFM-20B 85dB Active Buzzer Alarm — DC 3–24V, Continuous Sound, Arduino \u0026amp; Industrial\u003c\/h2\u003e\u003cp\u003eThe SFM-20B is a high-decibel active buzzer alarm module rated at 85dB sound pressure level, operating from DC 3V to 24V. As an active buzzer, it contains an internal oscillator and produces a continuous tone immediately when power is applied — no PWM or frequency signal required from the microcontroller. With a wide 3–24V supply range and -40°C to +80°C operating temperature, it is suitable for Arduino alarm systems, industrial alert indicators, security panels, and any application requiring a loud, reliable audible alarm.\u003c\/p\u003e\u003ch3\u003eKey Specifications\u003c\/h3\u003e\u003ctable\u003e\n\u003ctr\u003e\n\u003cth\u003eParameter\u003c\/th\u003e\n\u003cth\u003eValue\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eModel\u003c\/td\u003e\n\u003ctd\u003eSFM-20B\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eType\u003c\/td\u003e\n\u003ctd\u003eActive buzzer (internal oscillator)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSound Pressure Level\u003c\/td\u003e\n\u003ctd\u003e85dB (at 10cm)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperating Voltage\u003c\/td\u003e\n\u003ctd\u003eDC 3V – 24V\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eRated Voltage\u003c\/td\u003e\n\u003ctd\u003eDC 12V (typical)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCurrent Consumption\u003c\/td\u003e\n\u003ctd\u003e~30–50mA (at 12V)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSound Type\u003c\/td\u003e\n\u003ctd\u003eContinuous tone\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFrequency\u003c\/td\u003e\n\u003ctd\u003e~2300Hz (internal oscillator)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperating Temperature\u003c\/td\u003e\n\u003ctd\u003e-40°C to +80°C\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eConnection\u003c\/td\u003e\n\u003ctd\u003e2-wire (+ and −)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\u003ch3\u003eActive Buzzer vs Passive Buzzer\u003c\/h3\u003e\u003ctable\u003e\n\u003ctr\u003e\n\u003cth\u003eFeature\u003c\/th\u003e\n\u003cth\u003eActive Buzzer (SFM-20B)\u003c\/th\u003e\n\u003cth\u003ePassive Buzzer\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInternal oscillator\u003c\/td\u003e\n\u003ctd\u003eYes — produces sound on DC power\u003c\/td\u003e\n\u003ctd\u003eNo — requires PWM signal\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eControl\u003c\/td\u003e\n\u003ctd\u003eSimple ON\/OFF (GPIO or relay)\u003c\/td\u003e\n\u003ctd\u003ePWM frequency control needed\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSound\u003c\/td\u003e\n\u003ctd\u003eFixed frequency continuous tone\u003c\/td\u003e\n\u003ctd\u003eVariable frequency, melodies\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eVolume\u003c\/td\u003e\n\u003ctd\u003eHigher (85dB+)\u003c\/td\u003e\n\u003ctd\u003eLower (typically 70–80dB)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBest for\u003c\/td\u003e\n\u003ctd\u003eAlarm, alert, industrial indicator\u003c\/td\u003e\n\u003ctd\u003eMusic, variable tone, melody\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/table\u003e\u003ch3\u003eWhy Choose SFM-20B?\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003e85dB sound level\u003c\/strong\u003e — loud enough for industrial environments and security alarms\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e3–24V wide range\u003c\/strong\u003e — works from 3.3V (ESP32 direct), 5V (Arduino), 12V (industrial), and 24V (PLC)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eActive design\u003c\/strong\u003e — simple ON\/OFF control, no PWM or frequency programming needed\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e-40°C to +80°C\u003c\/strong\u003e — industrial temperature range for outdoor and harsh environment use\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eContinuous tone\u003c\/strong\u003e — persistent alarm sound until power is removed\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eCompatible With \/ Common Use Cases\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eArduino alarm system\u003c\/strong\u003e: Drive via NPN transistor (BC547) or MOSFET from Arduino GPIO — GPIO HIGH triggers alarm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIndustrial alert indicator\u003c\/strong\u003e: 12V or 24V buzzer on PLC output for machine fault alarm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSecurity panel\u003c\/strong\u003e: Door\/window sensor alarm buzzer in home security system\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTemperature alarm\u003c\/strong\u003e: Trigger buzzer when temperature sensor exceeds threshold\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePower-on indicator\u003c\/strong\u003e: Brief buzzer beep on system startup for status confirmation\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\u003cp\u003e\u003cstrong\u003eQ: Can I drive SFM-20B directly from Arduino GPIO pin?\u003c\/strong\u003e\u003cbr\u003eA: At 3–5V, the SFM-20B draws ~10–20mA, which is within Arduino GPIO limits (40mA max). However, for reliable operation and to protect the GPIO pin, use an NPN transistor (BC547, 2N2222) as a switch: GPIO → 1kΩ base resistor → transistor base; collector to buzzer negative; buzzer positive to 5V; emitter to GND. This allows the buzzer to draw current from the 5V rail, not the GPIO pin.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eQ: How do I control SFM-20B with a relay module?\u003c\/strong\u003e\u003cbr\u003eA: Connect the relay NO (normally open) contact in series with the buzzer power supply. When the relay coil is energized (by Arduino GPIO via relay module), the NO contact closes and powers the buzzer. This provides complete electrical isolation between the Arduino and the buzzer circuit, ideal for 12V or 24V industrial buzzer applications.\u003c\/p\u003e\u003cp\u003e\u003cstrong\u003eQ: Can I make the SFM-20B beep intermittently instead of continuously?\u003c\/strong\u003e\u003cbr\u003eA: Yes — control the power to the buzzer with a transistor or relay driven by Arduino PWM or timed GPIO switching. Use \u003ccode\u003edigitalWrite(pin, HIGH); delay(500); digitalWrite(pin, LOW); delay(500);\u003c\/code\u003e for 0.5s on \/ 0.5s off beeping. The buzzer itself always produces a continuous tone when powered — intermittent beeping is achieved by switching the power on and off.\u003c\/p\u003e\u003ch3\u003ePackage Contents\u003c\/h3\u003e\u003cul\u003e\u003cli\u003e1× SFM-20B 85dB Active Buzzer Alarm Module\u003c\/li\u003e\u003c\/ul\u003e","brand":"Keszoox","offers":[{"title":"10PCS","offer_id":46991470592235,"sku":"14:351074#10PCS","price":13.84,"currency_code":"USD","in_stock":true},{"title":"1PCS","offer_id":46991470625003,"sku":"14:1202#1PCS","price":5.72,"currency_code":"USD","in_stock":true},{"title":"5PCS","offer_id":46991470657771,"sku":"14:350852#5PCS","price":6.32,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0677\/1005\/8731\/files\/sfm-20b-high-decibel-active-buzzer.webp?v=1761633984","url":"https:\/\/keszoox.com\/products\/sfm-20b-85db-active-buzzer-alarm-dc3-24v-continuous-arduino-industrial","provider":"Keszoox","version":"1.0","type":"link"}