How to Use Whisker Limit Switch: Examples, Pinouts, and Specs

A whisker limit switch is a tactile sensor that is widely used in the field of robotics and automation. It operates by making physical contact with an object through a flexible, wire-like actuator known as a whisker. This simple yet effective component is essential for providing feedback on the position of mechanical parts, ensuring precision and safety in various applications.

• Robotics: To detect the position of robotic arms or end-effectors.
• CNC Machines: To establish reference points for machining operations.
• 3D Printers: To calibrate the print bed or determine the home position.
• Safety Mechanisms: To prevent machinery from exceeding its operational limits.

• Voltage Rating: 5V to 24V DC
• Current Rating: 100mA (max)
• Contact Type: Normally Open (NO)
• Mechanical Life: 1 million cycles (min)
• Operating Temperature: -10°C to 70°C

1. Connect the Common Pin: Depending on your circuit design, connect the common pin to either the ground or Vcc.
2. Choose NO/NC Configuration: Connect your load to the Normally Open or Normally Closed pin based on the desired behavior.
3. Mount the Switch: Secure the switch in a position where the whisker can make contact with the moving part.
4. Wire to Control Circuitry: Connect the output of the switch to the input of a microcontroller or relay module to process the switch signal.

• Debouncing: Implement software debouncing to account for mechanical contact bounce.
• Mounting: Ensure the whisker has enough freedom of movement and is not overly bent or stressed.
• Environmental Factors: Avoid placing the switch in environments with high moisture or dust levels that could affect its performance.

// Define the pin connected to the limit switch
const int limitSwitchPin = 2;

void setup() {
  // Set the limit switch pin as an input
  pinMode(limitSwitchPin, INPUT_PULLUP);
  // Initialize serial communication at 9600 bits per second
  Serial.begin(9600);
}

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

  // Check if the switch is pressed (assuming NO configuration)
  if (switchState == LOW) {
    // The whisker has made contact
    Serial.println("Whisker is in contact");
  } else {
    // The whisker is not in contact
    Serial.println("Whisker is not in contact");
  }

  // Delay a bit for debounce
  delay(50);
}

• Switch Does Not Respond: Ensure that the whisker is properly positioned to make contact and that all connections are secure.
• False Triggers: Implement debouncing in your code or check for environmental interference.

• Debouncing: Use software debouncing by adding a delay after detecting a switch change or by checking the switch state multiple times.
• Connection Check: Verify that the switch is correctly wired to the control circuitry and that there are no loose connections.

• Q: Can I use the whisker limit switch with an AC power source?

  • A: No, this switch is designed for low-voltage DC applications only.

• Q: How do I know if my switch is in NO or NC configuration?

  • A: You can test the switch with a multimeter in continuity mode. The NO pin will only show continuity when the whisker is activated, while the NC pin will show continuity when the whisker is not activated.

• Q: Is it possible to adjust the sensitivity of the whisker?

  • A: The sensitivity is not directly adjustable, but you can bend the whisker to change the point at which it makes contact with the object.