{"product_id":"ky-021-mini-magnetic-reed-switch-sensor-module-for-arduino","title":"KY-021 Mini Magnetic Reed Switch Sensor Module for Arduino","description":"\n\u003ch2\u003eKY-021 Mini Magnetic Reed Switch Sensor Module for Arduino\u003c\/h2\u003e\n\n\u003cp\u003eBuy the \u003cstrong\u003eKY-021 Mini Magnetic Reed Switch Sensor Module\u003c\/strong\u003e online in Pakistan from \u003cstrong\u003eRobostan.pk\u003c\/strong\u003e. This compact digital magnetic detection module is designed for Arduino, ESP32, Raspberry Pi, robotics, home automation, door security alarms, and DIY electronics projects.\u003c\/p\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eKY-021 Magnetic Reed Sensor\u003c\/strong\u003e contains a normally open reed switch that responds to a nearby magnetic field. When a suitable magnet approaches the sensor, its internal metal contacts close, producing a change in the digital output signal that can be detected by a compatible microcontroller.\u003c\/p\u003e\n\n\u003cp\u003eFeaturing a \u003cstrong\u003e3.3V to 5V operating voltage, three-pin interface, and compact PCB design\u003c\/strong\u003e, the KY-021 is an affordable solution for magnetic proximity detection, door and window monitoring, position sensing, and electronic switching experiments.\u003c\/p\u003e\n\n\u003ch3\u003eKey Features\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eKY-021 mini magnetic reed switch module\u003c\/li\u003e\n\u003cli\u003eNormally open (NO) magnetic switch\u003c\/li\u003e\n\u003cli\u003eContactless magnetic activation\u003c\/li\u003e\n\u003cli\u003eOperating voltage: 3.3V to 5V DC\u003c\/li\u003e\n\u003cli\u003eDigital HIGH\/LOW signal output\u003c\/li\u003e\n\u003cli\u003eThree-pin interface: Signal, VCC and GND\u003c\/li\u003e\n\u003cli\u003eTypical onboard 10kΩ pull-up resistor\u003c\/li\u003e\n\u003cli\u003eSealed glass reed switch construction\u003c\/li\u003e\n\u003cli\u003eNo external magnetic field sensor IC required\u003c\/li\u003e\n\u003cli\u003eCompatible with Arduino digital input pins\u003c\/li\u003e\n\u003cli\u003eSuitable for ESP32 and Raspberry Pi GPIO projects\u003c\/li\u003e\n\u003cli\u003eCompact and lightweight PCB\u003c\/li\u003e\n\u003cli\u003eUseful for door and window security alarms\u003c\/li\u003e\n\u003cli\u003eSuitable for magnetic position detection\u003c\/li\u003e\n\u003cli\u003eEasy integration into automation projects\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eProduct Name:\u003c\/strong\u003e KY-021 Mini Magnetic Reed Switch Sensor Module\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eModel Number:\u003c\/strong\u003e KY-021\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAlternative PCB Marking:\u003c\/strong\u003e HW-497 on some versions\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSensor Type:\u003c\/strong\u003e Magnetic Reed Switch\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSwitch Configuration:\u003c\/strong\u003e Normally Open (NO)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDetection Method:\u003c\/strong\u003e Magnetic Field Activated Contacts\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOperating Voltage:\u003c\/strong\u003e 3.3V to 5V DC\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOutput Type:\u003c\/strong\u003e Digital\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTypical Output When Magnet Is Detected:\u003c\/strong\u003e LOW\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTypical Output Without Magnet:\u003c\/strong\u003e HIGH\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eOnboard Resistor:\u003c\/strong\u003e 10kΩ\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eInterface:\u003c\/strong\u003e Three-Pin Header\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eConnection Pins:\u003c\/strong\u003e S, + and -\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eTypical PCB Dimensions:\u003c\/strong\u003e Approximately 18.5 × 15mm\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCompatible Platforms:\u003c\/strong\u003e Arduino, ESP32, Raspberry Pi and Other Compatible Controllers\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eMounting:\u003c\/strong\u003e PCB Sensor Module\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eApplications\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eArduino magnetic detection projects\u003c\/li\u003e\n\u003cli\u003eDoor and window security alarms\u003c\/li\u003e\n\u003cli\u003eMagnetic proximity sensing\u003c\/li\u003e\n\u003cli\u003eSmart home automation systems\u003c\/li\u003e\n\u003cli\u003eElectronic door monitoring\u003c\/li\u003e\n\u003cli\u003eCabinet and drawer position detection\u003c\/li\u003e\n\u003cli\u003eRobotics magnetic switching\u003c\/li\u003e\n\u003cli\u003eContactless position monitoring\u003c\/li\u003e\n\u003cli\u003eDIY magnetic security systems\u003c\/li\u003e\n\u003cli\u003eESP32 IoT monitoring projects\u003c\/li\u003e\n\u003cli\u003eRaspberry Pi GPIO applications\u003c\/li\u003e\n\u003cli\u003eEducational electronics experiments\u003c\/li\u003e\n\u003cli\u003eMechanical movement detection using magnets\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eHow Does the KY-021 Magnetic Reed Switch Work?\u003c\/h3\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eKY-021 Magnetic Reed Switch\u003c\/strong\u003e contains two flexible metal contacts sealed inside a small glass capsule.\u003c\/p\u003e\n\n\u003cp\u003eUnder normal conditions, the contacts remain separated, creating an open circuit.\u003c\/p\u003e\n\n\u003cp\u003eWhen a suitable magnet approaches, the magnetic field causes the contacts to attract each other and close the circuit.\u003c\/p\u003e\n\n\u003cp\u003eWhen the magnet is removed, the contacts return to their original open state.\u003c\/p\u003e\n\n\u003cp\u003eA connected Arduino or other microcontroller detects these changes through the module's digital output pin.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eImportant:\u003c\/strong\u003e The KY-021 is a basic magnetic switch. It does not measure magnetic field strength, magnet distance, or precise position.\u003c\/p\u003e\n\n\u003ch3\u003eKY-021 Sensor Pinout\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eS (Signal):\u003c\/strong\u003e Digital magnetic detection output\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e+ (VCC):\u003c\/strong\u003e Positive power supply, 3.3V or 5V\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003e- (GND):\u003c\/strong\u003e Ground connection\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eOn a commonly documented KY-021 module, the output is HIGH when no magnet is detected and LOW when the reed contacts close.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eNote:\u003c\/strong\u003e Verify the pin labels and switching behavior on your actual PCB before installation.\u003c\/p\u003e\n\n\u003ch3\u003eArduino Compatibility\u003c\/h3\u003e\n\n\u003cp\u003eThe KY-021 is compatible with Arduino UNO, Arduino Nano, Arduino Mega, and other microcontrollers with digital input pins.\u003c\/p\u003e\n\n\u003cp\u003eA typical Arduino UNO connection is:\u003c\/p\u003e\n\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eKY-021 S:\u003c\/strong\u003e Arduino digital pin D2\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eKY-021 +:\u003c\/strong\u003e Arduino 5V\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eKY-021 -:\u003c\/strong\u003e Arduino GND\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThe Arduino digitalRead() function can monitor the output and determine whether a magnet is close enough to activate the switch.\u003c\/p\u003e\n\n\u003cp\u003eThis makes the KY-021 suitable for simple magnetic detection and security alarm programming.\u003c\/p\u003e\n\n\u003ch3\u003eESP32 and Raspberry Pi Compatibility\u003c\/h3\u003e\n\n\u003cp\u003eThe KY-021 can also be used with ESP32 and Raspberry Pi GPIO inputs.\u003c\/p\u003e\n\n\u003cp\u003eFor these 3.3V systems, power the module from a suitable 3.3V supply so the output signal remains within the controller's permitted input voltage range.\u003c\/p\u003e\n\n\u003cp\u003eThe sensor can then be monitored through a digital GPIO input using appropriate software.\u003c\/p\u003e\n\n\u003ch3\u003eDoor and Window Magnetic Alarm Projects\u003c\/h3\u003e\n\n\u003cp\u003eThe \u003cstrong\u003eKY-021 Magnetic Reed Switch Module\u003c\/strong\u003e is useful for building door and window monitoring systems.\u003c\/p\u003e\n\n\u003cp\u003eA magnet can be mounted on a moving door or window, with the sensor positioned nearby on the fixed frame.\u003c\/p\u003e\n\n\u003cp\u003eAs the door opens or closes, the position of the magnet changes, causing the sensor to switch between its digital output states.\u003c\/p\u003e\n\n\u003cp\u003eA microcontroller can use this information to activate a buzzer, control a status LED, or send a notification through a compatible wireless system.\u003c\/p\u003e\n\n\u003ch3\u003eKY-021 vs KY-003 Hall Effect Sensor\u003c\/h3\u003e\n\n\u003cp\u003eBoth the KY-021 and KY-003 detect magnetic fields, but they use different sensing methods.\u003c\/p\u003e\n\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eKY-021:\u003c\/strong\u003e Uses physical metal reed contacts that open and close in response to a magnetic field.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eKY-003:\u003c\/strong\u003e Uses a solid-state Hall Effect sensor IC to produce a digital magnetic detection signal.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eThe KY-021 is useful for simple magnetic switching, while the KY-003 is suited to applications requiring solid-state magnetic sensing without mechanical contacts.\u003c\/p\u003e\n\n\u003ch3\u003eAdvantages of the KY-021\u003c\/h3\u003e\n\n\u003cp\u003e\u003cstrong\u003eSimple Magnetic Detection:\u003c\/strong\u003e Provides a digital switching signal when a suitable magnet approaches.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eLow-Voltage Operation:\u003c\/strong\u003e Compatible with commonly used 3.3V and 5V microcontroller systems.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eCompact Design:\u003c\/strong\u003e Easy to incorporate into small electronic monitoring projects.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eSimple Interface:\u003c\/strong\u003e Uses standard digital input connections without complex communication protocols.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eVersatile Applications:\u003c\/strong\u003e Useful for door alarms, contactless switching, magnetic position sensing, and educational electronics.\u003c\/p\u003e\n\n\u003ch3\u003eImportant Usage Notes\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eThe KY-021 uses a mechanical reed switch, not a Hall Effect sensor.\u003c\/li\u003e\n\u003cli\u003eMagnetic detection distance depends on magnet strength, orientation, and installation position.\u003c\/li\u003e\n\u003cli\u003eDo not assume a fixed detection distance for every magnet.\u003c\/li\u003e\n\u003cli\u003eMechanical contact bouncing may occur during switching.\u003c\/li\u003e\n\u003cli\u003eSoftware debouncing may be required for stable readings.\u003c\/li\u003e\n\u003cli\u003eThe glass reed switch is fragile and should not be bent or crushed.\u003c\/li\u003e\n\u003cli\u003eVerify the actual module pinout before applying power.\u003c\/li\u003e\n\u003cli\u003eUse a regulated 3.3V or 5V supply as appropriate.\u003c\/li\u003e\n\u003cli\u003eDo not connect high-current electrical loads directly to the digital signal output.\u003c\/li\u003e\n\u003cli\u003eUse a separate suitable relay or driver circuit when switching external loads.\u003c\/li\u003e\n\u003cli\u003eThe module should not be used as the sole protective device in safety-critical systems.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003ePackage Contents\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e1 × KY-021 Mini Magnetic Reed Switch Sensor Module\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003cp\u003eMagnet, Arduino board, and connecting wires are not included unless specified separately.\u003c\/p\u003e\n\n\u003ch3\u003eBuy KY-021 Magnetic Reed Switch Module in Pakistan\u003c\/h3\u003e\n\n\u003cp\u003eLooking for a \u003cstrong\u003eKY-021 Mini Magnetic Reed Switch Sensor Module in Pakistan\u003c\/strong\u003e? Shop online at \u003cstrong\u003eRobostan.pk\u003c\/strong\u003e for magnetic sensors, reed switches, Arduino modules, ESP32 boards, Raspberry Pi accessories, robotics components, and DIY electronics supplies.\u003c\/p\u003e\n\n\u003cp\u003eThe KY-021 is suitable for students, engineers, robotics enthusiasts, and electronics developers building magnetic proximity detection and automation projects.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eOrder your KY-021 Magnetic Reed Sensor from Robostan.pk\u003c\/strong\u003e with nationwide delivery across Pakistan, including Lahore, Karachi, Islamabad, Rawalpindi, Faisalabad, Multan, Peshawar, and other cities.\u003c\/p\u003e\n\n\u003cp\u003e\u003cstrong\u003eRobostan.pk – Build. Innovate. Create.\u003c\/strong\u003e\u003c\/p\u003e\n","brand":"ROBOSTAN","offers":[{"title":"Default Title","offer_id":68374694723950,"sku":null,"price":180.0,"currency_code":"PKR","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/1019\/7391\/8062\/files\/ChatGPTImageNov13_2026_05_05_22PM-5.png?v=1794582649","url":"https:\/\/robostan.pk\/products\/ky-021-mini-magnetic-reed-switch-sensor-module-for-arduino","provider":"ROBOSTAN","version":"1.0","type":"link"}