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

A flush switch is a momentary tactile switch that is commonly used in electronic circuits. Its design allows it to be mounted so that its surface is flush with the panel or board, providing a sleek and unobtrusive appearance. When pressed, the switch momentarily makes or breaks an electrical connection, which can be used to control various aspects of a circuit such as turning on a light, starting a process, or inputting a signal to a microcontroller.

• User input for electronic devices
• Reset or interrupt buttons on printed circuit boards
• Doorbell or intercom systems
• Keyboard keys or game controller buttons
• Prototype and hobbyist projects, often interfaced with microcontrollers like Arduino

• Switch Type: Momentary tactile switch
• Contact Configuration: Normally open (NO)
• Actuation Force: Typically between 100g to 300g
• Rated Voltage: Often 12V DC
• Rated Current: Usually around 50mA
• Operating Temperature Range: -20°C to 70°C

Note: The pin configuration may vary depending on the specific model of the flush switch. Always refer to the manufacturer's datasheet for exact details.

1. Identify the Pins: Locate the Normally Open (NO) and Common (COM) pins on the switch.
2. Circuit Integration: Connect the Common (COM) pin to one side of the power source or signal line.
3. Load Connection: Connect the Normally Open (NO) pin to the load (e.g., LED, relay, microcontroller input pin).
4. Mounting: Secure the switch in place so that it is flush with the panel or board surface.
5. Testing: Press the switch to ensure it momentarily closes the circuit, activating the load.

• Ensure the switch's voltage and current ratings are not exceeded by the circuit.
• Use a pull-up or pull-down resistor when connecting to a microcontroller to ensure a stable signal.
• Avoid excessive force to prevent damage to the switch mechanism.
• Consider the environmental conditions where the switch will be used and ensure it meets the operating temperature range.

• Switch Does Not Actuate: Check for proper mounting and that the actuation force is sufficient.
• Intermittent Connection: Inspect for loose wiring or solder joints.
• No Response in Circuit: Verify that the switch's ratings match the circuit requirements.

• Double-check the wiring against the circuit diagram.
• Test the switch with a multimeter to ensure it is functioning correctly.
• Replace the switch if it shows signs of physical damage or wear.

Q: Can I use a flush switch with an AC circuit? A: While some flush switches may be rated for low-voltage AC applications, always check the manufacturer's specifications before use.

Q: How do I know if the switch is momentary? A: A momentary switch will only maintain its closed state while being pressed and will return to its open state upon release.

Q: What is the lifespan of a flush switch? A: The lifespan can vary, but many are rated for hundreds of thousands of cycles. Check the datasheet for the specific model.

// Define the pin connected to the flush switch
const int flushSwitchPin = 2;

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

void loop() {
  // Check the state of the switch
  int switchState = digitalRead(flushSwitchPin);
  
  // If the switch is pressed (circuit closed), the pin reads LOW
  if (switchState == LOW) {
    Serial.println("Switch Pressed");
    // Add code here to respond to switch press
  } else {
    // Add code here to respond to switch release
  }
  
  // Debounce delay to avoid reading noise as multiple presses
  delay(50);
}

Note: The above code assumes the use of an internal pull-up resistor. When the switch is pressed, the pin is connected to ground, resulting in a LOW reading.

This documentation provides a comprehensive overview of the flush switch, its specifications, usage, and troubleshooting. For specific projects or advanced applications, always refer to the datasheet and additional resources provided by the manufacturer.