ESP32 KY-021 Mini Magnetic Reed Switch Module Pinout, Wiring and more
Overview
The KY-021 is a mini magnetic reed switch module that detects the presence of a magnetic field. It provides a digital signal output, making it suitable for applications like security systems, position sensors, and magnetic field detection projects.
About KY-021 Mini Magnetic Reed Switch Module
The KY-021 Mini Magnetic Reed Switch Module is designed to detect the presence of a magnetic field. It contains a reed switch that closes its contacts when exposed to a magnetic field, allowing current to flow through. This module operates at voltages between 3.3V and 5V, making it compatible with various microcontrollers like Arduino and ESP32. It’s commonly used in applications such as door and window sensors, position detection, and other projects requiring magnetic field detection.
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KY-021 Datasheet and Technical Specifications
KY-021 Pinout Diagram
The VCC pin is used to supply power to the sensor, and it typically requires 3.3V or 5V (refer to the datasheet for specific voltage requirements). The GND pin is the ground connection and must be connected to the ground of your ESP32.
Pin (-):Connects to ground (GND).Pin (middle):Connects to VCC (3.3V to 5V).Pin (S):Outputs the digital signal; connect to a digital input on your microcontroller.
KY-021 Wiring with ESP32
KY-021 Pin (-):Connect to ESP32GND.KY-021 Pin (middle):Connect to ESP323.3V.KY-021 Pin (S):Connect to a digital GPIO pin on ESP32 (e.g.,GPIO4).
KY-021 Troubleshooting Guide
Common Issues
❌ No Response from Sensor
Issue: The sensor does not output any signal when a magnet is nearby.
Solutions:
- Verify that all connections are secure and correctly placed.
- Ensure the module is receiving the appropriate voltage (3.3V to 5V).
- Check if the microcontroller's digital input pin is correctly configured.
- Test the reed switch with a multimeter to confirm it closes when exposed to a magnetic field.
⚠️ False Triggering
Issue: The sensor outputs a signal without a magnet nearby.
Solutions:
- Ensure stable mounting to prevent unintended movements.
- Check for loose connections or interference from nearby electronic components.
- Implement software debouncing to filter out spurious signals.
- Verify that there are no stray magnetic fields in the environment causing false triggers.
Debugging Tips
🔍 Serial Monitor
Use the Serial Monitor to check for error messages and verify the sensor's output. Add debug prints in your code to track the sensor's state.
⚡ Voltage Checks
Use a multimeter to verify voltage levels and check for continuity in your connections. Ensure the power supply is stable and within the sensor's requirements.
Additional Resources
KY-021 Code Examples
Arduino Example
int reed_magnet = 10; // Declaration of the sensor input pin
int value; // Temporary variable
void setup() {
pinMode(reed_magnet, INPUT); // Initialization sensor pin
Serial.begin(9600); // Initialization of the serial monitor
Serial.println("KY-021 Magnetic field detection");
}
void loop() {
// The current signal at the sensor is read out
value = digitalRead(reed_magnet);
// If a signal could be detected, this is displayed on the serial monitor.
if (value == LOW) {
Serial.println("Magnetic field detected");
delay(100); // 100 ms break
}
}This Arduino code sets up the KY-021 reed switch on digital pin 10. It reads the digital value corresponding to the presence of a magnetic field and prints a message to the serial monitor when a magnetic field is detected.
ESP-IDF Example
#include <stdio.h>
#include "freertos/FreeRTOS.h"
#include "freertos/task.h"
#include "driver/gpio.h"
#define REED_SWITCH_PIN GPIO_NUM_4
void app_main(void) {
gpio_config_t io_conf = {
.pin_bit_mask = (1ULL << REED_SWITCH_PIN),
.mode = GPIO_MODE_INPUT,
.pull_up_en = GPIO_PULLUP_ENABLE,
.pull_down_en = GPIO_PULLDOWN_DISABLE,
.intr_type = GPIO_INTR_DISABLE
};
gpio_config(&io_conf);
printf("KY-021 Magnetic Field Detection Test\n");
while (1) {
int level = gpio_get_level(REED_SWITCH_PIN);
if (level == 0) {
printf("Magnetic field detected\n");
vTaskDelay(pdMS_TO_TICKS(100)); // 100 ms delay
}
vTaskDelay(pdMS_TO_TICKS(100));
}
}This ESP-IDF code configures GPIO4 as an input with an internal pull-up resistor for the KY-021 reed switch. It continuously checks the pin state and prints a message when a magnetic field is detected.
ESPHome Example
binary_sensor:
- platform: gpio
pin:
number: GPIO4
mode: INPUT_PULLUP
name: "KY-021 Magnetic Reed Switch"
filters:
- delayed_on: 50ms
- delayed_off: 50ms
on_press:
- then:
- lambda: |-
ESP_LOGD("sensor", "Magnetic field detected!");This ESPHome configuration sets up the KY-021 reed switch as a binary sensor on GPIO4. The internal pull-up resistor is enabled, and debounce filters are applied to prevent false triggers. When the sensor detects a magnetic field, a log message is generated.
PlatformIO Example
platformio.ini
[env:esp32]
platform = espressif32
board = esp32dev
framework = arduinoPlatformIO Example Code
#include <Arduino.h>
#define REED_SWITCH_PIN 4
void setup() {
pinMode(REED_SWITCH_PIN, INPUT_PULLUP);
Serial.begin(115200);
Serial.println("KY-021 Magnetic Field Detection Test");
}
void loop() {
if (digitalRead(REED_SWITCH_PIN) == LOW) {
Serial.println("Magnetic field detected");
delay(100);
}
delay(100);
}This PlatformIO code configures GPIO4 as an input with a pull-up resistor for the KY-021 reed switch. It detects magnetic fields and prints a message when a field is detected.
MicroPython Example
import machine
import time
REED_SWITCH_PIN = machine.Pin(4, machine.Pin.IN, machine.Pin.PULL_UP)
while True:
if REED_SWITCH_PIN.value() == 0:
print("Magnetic field detected")
time.sleep(0.1)
time.sleep(0.1)This MicroPython script configures GPIO4 as an input with an internal pull-up resistor for the KY-021 reed switch. It continuously checks the sensor state and prints a message when a magnetic field is detected.
Conclusion
The ESP32 KY-021 Mini Magnetic Reed Switch Module is a powerful KY-0xx module sensor that offers excellent performance and reliability. With support for multiple development platforms including Arduino, ESP-IDF, ESPHome, PlatformIO, and MicroPython, it's a versatile choice for your IoT projects.
For optimal performance, ensure proper wiring and follow the recommended configuration for your chosen development platform.
Always verify power supply requirements and pin connections before powering up your project to avoid potential damage.
