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Reed Switch Module-DIgital Output (KY-021)

SKU: IWPN6KEPAQ
★★★★ ★ ★
4.5 (70 reviews)
The KY-021 Reed Switch Module is a compact magnetic field detection module designed to detect the presence or absence of a nearby magnet. It uses a normally open (NO) reed switch enclosed in a hermetically sealed glass tube that closes when exposed to a magnetic field, producing a digital output signal. Unlike the KY-025, the KY-021 provides only a digital...
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The KY-021 Reed Switch Module is a compact magnetic field detection module designed to detect the presence or absence of a nearby magnet. It uses a normally open (NO) reed switch enclosed in a hermetically sealed glass tube that closes when exposed to a magnetic field, producing a digital output signal.

Unlike the KY-025, the KY-021 provides only a digital output, making it ideal for simple magnetic ON/OFF detection applications. The module includes an onboard pull-up resistor, allowing it to interface directly with Arduino, ESP32, STM32, Raspberry Pi Pico, and other microcontrollers without requiring additional external components.

The KY-021 is commonly used in door and window security systems, position sensing, limit switches, magnetic counters, proximity detection, industrial automation, and robotics applications. Its simple design, reliable operation, and long service life make it an excellent choice for magnetic sensing projects.

Key Features

  • High-quality normally open reed switch
  • Digital magnetic field detection
  • Detects the presence of magnets
  • Simple ON/OFF output
  • Built-in pull-up resistor
  • Fast response time
  • Low power consumption
  • Compact PCB module design
  • Hermetically sealed reed switch
  • Long mechanical life
  • Easy microcontroller interfacing
  • Compatible with Arduino, ESP32, STM32, and Raspberry Pi
  • Suitable for security and automation applications
  • Ideal for educational and DIY electronics projects

Shipping & Returns

Orders placed before 3 PM IST will be shipped on the same day (excluding Sundays and Public holidays) through our shipping partners. In rare cases, the pickup may get delayed during Public holidays / Bandh / Environmental disturbances.

Specifications

Specifications:

Module Type: Reed Switch Magnetic Sensor Module
Model: KY-021
Sensor Type: Normally Open Reed Switch
Detection Principle: Magnetic Field Detection
Operating Voltage: 3.3V to 5V DC
Operating Current: Less Than 5mA
Output Type: Digital Output
Digital Output Logic: TTL Compatible
Switch Type: Normally Open (NO) Reed Switch
Detection Method: Magnetic Contact Switching
Detection Distance: Approximately 10mm to 20mm (Depends on Magnet Strength)
Built-in Pull-Up Resistor: Yes
Response Time: Fast Response
Interface Pins: VCC, GND, S
Operating Temperature: -20°C to +70°C
Storage Temperature: -40°C to +85°C
Module Dimensions: Approximately 19mm × 18.5mm × 9mm
Mounting Type: Through-Hole Module
Compatibility: Arduino, ESP32, STM32, Raspberry Pi Pico, AVR, PIC

Additional Resources

Reed Switch.PDF

FAQ

1. What is the KY-021 Reed Switch Module used for?

The KY-021 is used to detect the presence of a magnet in applications such as door and window alarms, position sensing, limit switches, robotics, and industrial automation.

2. How does the KY-021 Reed Switch Module work?

The module contains a normally open reed switch that closes when a magnetic field is brought near it, causing the digital output to change state.

3. Can the KY-021 be connected directly to Arduino and ESP32 boards?

Yes, the module operates from 3.3V to 5V and provides a TTL-compatible digital output that can be directly connected to Arduino, ESP32, STM32, Raspberry Pi Pico, and other microcontrollers.

4. What is the difference between the KY-021 and KY-025 modules?

The KY-021 provides only a digital ON/OFF output for magnetic field detection, while the KY-025 offers both analog and digital outputs along with an adjustable comparator threshold.

5. Does the KY-021 require a power supply to operate?

The reed switch itself is a passive mechanical component, but the module requires a 3.3V to 5V supply so that it can provide a clean digital output signal to a connected microcontroller.