How to Use Micro Switch: Examples, Pinouts, and Specs

A micro switch, also known as a miniature snap-action switch, is a small, high-precision switch that operates using a tipping-point mechanism with very little physical force. It is widely used in various applications, including home appliances, industrial equipment, and consumer electronics, to detect the presence or absence of objects, changes in position, or to provide a user with tactile feedback.

• Safety interlocks in appliances (e.g., microwave door switches)
• Position sensing in machinery (e.g., CNC machines)
• End-stop switches in 3D printers
• Level switches in vending machines
• Keyboard keys in computer peripherals

• Voltage Rating: Typically ranges from 5V to 250V
• Current Rating: Can vary from a few milliamps to around 10-15A
• Contact Configuration: Normally open (NO), normally closed (NC), or changeover (SPDT)
• Operating Force: The force required to actuate the switch, usually measured in grams or newtons
• Mechanical Life: The number of actuations the switch can endure, often in the millions

1. Identify the Pins: Refer to the pin configuration table to identify the Common (COM), Normally Open (NO), and Normally Closed (NC) pins.
2. Wiring: Connect the COM pin to one side of the control circuit. Connect either the NO or NC pin to the other side, depending on whether you want the circuit to be closed by default or only when the switch is actuated.
3. Mounting: Secure the micro switch in place so that the actuator will be properly engaged by the moving part of your application.
4. Testing: Before finalizing the installation, test the switch to ensure it actuates correctly and the circuit behaves as expected.

• Voltage and Current Ratings: Do not exceed the voltage and current ratings specified for the micro switch to avoid damage.
• Debouncing: Micro switches inherently provide a clean contact bounce profile, but in sensitive applications, consider implementing debouncing techniques.
• Environmental Factors: Consider the operating environment. Micro switches rated for high temperatures or with protective sealing may be necessary in harsh conditions.

• Intermittent Operation: This could be due to a loose connection or a worn-out switch. Check the wiring and replace the switch if necessary.
• No Actuation: Ensure that the actuator is properly engaged and that there is no obstruction. Also, verify that the switch is not damaged.

• Check Connections: Loose or corroded connections can cause issues. Inspect and clean or tighten connections as needed.
• Test with a Multimeter: Use a multimeter to check for continuity across the COM and NO/NC pins when the switch is actuated.
• Replace if Faulty: If the switch does not show continuity where expected or shows continuity without actuation, replace it.

Q: Can I use a micro switch with an Arduino? A: Yes, micro switches can be used with an Arduino for input detection. Ensure that the switch's voltage and current ratings are compatible with the Arduino's I/O pins.

Q: How do I know if my micro switch is working? A: You can test it with a multimeter set to the continuity function. When the actuator is pressed, you should hear a beep if the switch is functioning correctly.

Q: What is the difference between NO and NC contacts? A: NO contacts are open when the switch is at rest and close when actuated. NC contacts are closed at rest and open when actuated.

// Define the pin connected to the micro switch
const int microSwitchPin = 2;

void setup() {
  // Set the micro switch pin as an input
  pinMode(microSwitchPin, INPUT_PULLUP);
  Serial.begin(9600);
}

void loop() {
  // Read the state of the micro switch
  int switchState = digitalRead(microSwitchPin);

  // Check if the switch is pressed (assuming NO configuration)
  if (switchState == LOW) {
    // The switch is pressed
    Serial.println("Switch is pressed");
  } else {
    // The switch is not pressed
    Serial.println("Switch is not pressed");
  }

  // Add a small delay to prevent bouncing issues
  delay(50);
}

Note: The INPUT_PULLUP mode is used to enable the internal pull-up resistor, which ensures a stable state when the switch is open. The switch is connected between the pin and ground. When pressed, the pin reads LOW; when released, it reads HIGH due to the pull-up resistor.