How to Use Door MC-38: Examples, Pinouts, and Specs

The Door MC-38 is a magnetic reed switch commonly used as a sensor for detecting the opening and closing of doors and windows. It is a simple, yet effective component for security systems, home automation, and other applications where it is necessary to monitor the status of an entry point.

• Home and commercial security systems
• Automated lighting control when doors are opened or closed
• Monitoring access to restricted areas
• DIY projects involving entry detection

• Operating Voltage: Typically 100VDC
• Maximum Switching Current: 0.5A
• Maximum Carrying Current: 1.0A
• Contact Type: Normally Open (NO)
• Contact Resistance: <100 milliohms
• Recommended Mounting Method: Screw or adhesive pad

The Door MC-38 does not have traditional pins but has two parts: the reed switch and the magnet. The reed switch has two wires for connection.

1. Mounting: Install the reed switch on the door frame and the magnet on the door itself, ensuring they are aligned when the door is closed.
2. Wiring: Connect the red wire to the input of a digital pin on a microcontroller (e.g., Arduino) and the black wire to ground.
3. Pull-up Resistor: Use an internal or external pull-up resistor to keep the input HIGH when the door is closed and the circuit is open.

• Alignment: Proper alignment of the magnet and switch is crucial for accurate detection.
• Debouncing: Implement software debouncing to avoid false triggers due to mechanical vibrations.
• Cable Length: Keep the wires as short as possible to minimize interference and voltage drop.

// Define the pin connected to the Door MC-38
const int doorSensorPin = 2;

void setup() {
  // Set the door sensor pin as an input with an internal pull-up resistor
  pinMode(doorSensorPin, INPUT_PULLUP);
  // Initialize serial communication at 9600 bits per second
  Serial.begin(9600);
}

void loop() {
  // Read the state of the door sensor
  int doorState = digitalRead(doorSensorPin);

  // Check if the door is open (the reed switch is open and the input is HIGH)
  if (doorState == HIGH) {
    Serial.println("Door is open");
  } else {
    Serial.println("Door is closed");
  }

  // Delay for a bit to avoid spamming the serial output
  delay(500);
}

• Misalignment: The door sensor does not trigger when the door is opened or closed. Ensure the magnet and switch are properly aligned.
• Wiring Issues: If the sensor is not responding, check all connections for proper contact and ensure there are no breaks in the wires.
• False Triggers: If the sensor is triggering falsely, implement a debounce algorithm in your code.

• Test with a Multimeter: Use a multimeter to check for continuity when the door is closed. If there is no continuity, adjust the alignment or check the wiring.
• Software Debounce: Implement a simple debounce function in your code to filter out noise.
• Secure Mounting: Ensure that both the reed switch and magnet are securely mounted to prevent movement and misalignment.

Q: Can the Door MC-38 be used outdoors? A: Yes, but it should be protected from the elements to prevent corrosion and damage.

Q: What is the maximum distance the magnet can be from the switch? A: The maximum operating gap is typically around 15-25mm, but it's best to keep it as close as possible for reliable operation.

Q: Can I connect multiple Door MC-38 switches to a single Arduino? A: Yes, you can connect multiple switches to different digital pins on the Arduino, just ensure each has its own pull-up resistor if not using the internal one.