ESP32 KY-021 Mini Magnetic Reed Switch Module

🛠️ KY-021 Mini Magnetic Reed Switch Module Troubleshooting

This guide outlines a systematic approach to troubleshoot and resolve common problems with the . Start by confirming that the hardware connections are correct, as wiring mistakes are the most frequent cause of issues. If you are sure the connections are correct, follow the below steps to debug common issues.

❌ No Response from Sensor

⚠️ False Triggering

💻 Code Examples

Below you can find code examples of KY-021 Mini Magnetic Reed Switch Module with ESP32 in several frameworks:

• Arduino IDE
• ESP-IDF
• ESPHome
• PlatformIO
• MicroPython

If you encounter issues while using the KY-021 Mini Magnetic Reed Switch Module, check the Common Issues Troubleshooting Guide.

ESP32 KY-021 Arduino IDE Code Example

Example in Arduino IDE

Fill in your main Arduino IDE sketch file with the following code to use the KY-021 Mini Magnetic Reed Switch Module:

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.

Connect your ESP32 to your computer via a USB cable, Ensure the correct Board and Port are selected under Tools, Click the "Upload" button in the Arduino IDE to compile and upload the code to your ESP32.

ESP32 KY-021 ESP-IDF Code Example

Example in Espressif IoT Framework (ESP-IDF)

If you're using ESP-IDF to work with the KY-021 Mini Magnetic Reed Switch Module, here's how you can set it up and read data from the sensor. Fill in this code in the main ESP-IDF file:

#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.

Update the I2C pins (I2C_MASTER_SDA_IO and I2C_MASTER_SCL_IO) to match your ESP32 hardware setup, Use idf.py build to compile the project, Use idf.py flash to upload the code to your ESP32.

ESP32 KY-021 ESPHome Code Example

Example in ESPHome (Home Assistant)

Fill in this configuration in your ESPHome YAML configuration file (example.yml) to integrate the KY-021 Mini Magnetic Reed Switch Module

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.

Upload this code to your ESP32 using the ESPHome dashboard or the esphome run command.

ESP32 KY-021 PlatformIO Code Example

Example in PlatformIO Framework

For PlatformIO, make sure to configure the platformio.ini file with the appropriate environment and libraries, and then proceed with the code.

Configure platformio.ini

First, your platformio.ini should look like below. You might need to include some libraries as shown. Make sure to change the board to your ESP32:

[env:esp32]
platform = espressif32
board = esp32dev
framework = arduino

ESP32 KY-021 PlatformIO Example Code

Write this code in your PlatformIO project under the src/main.cpp file to use the KY-021 Mini Magnetic Reed Switch Module:

#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.

Upload the code to your ESP32 using the PlatformIO "Upload" button in your IDE or the pio run --target upload command.

ESP32 KY-021 MicroPython Code Example

Example in Micro Python Framework

Fill in this script in your MicroPython main.py file (main.py) to integrate the KY-021 Mini Magnetic Reed Switch Module with your ESP32.

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.

Upload this code to your ESP32 using a MicroPython-compatible IDE, such as Thonny, uPyCraft, or tools like ampy.