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

A float switch is an essential device used to detect and control the level of liquid within a tank or container. It operates on a simple mechanism: a buoyant float is attached to a switch, which activates as the liquid level rises or falls. This makes float switches ideal for applications such as automatic water level control in tanks, sump pump activation, and overflow prevention.

• Water level monitoring in tanks and sumps
• Automatic refilling or draining systems
• Overflow or dry-run protection for pumps
• Alarms for high or low water levels

• Operating Voltage: Typically 5V to 24V DC
• Max Switching Current: Often 0.5A to 1A (varies by model)
• Max Switching Voltage: Commonly up to 100V to 240V AC
• Temperature Range: Usually -10°C to 60°C (varies by model)
• Material: Often made of plastic (e.g., PP) or stainless steel for corrosion resistance

• Common (COM): Connects to the power supply.
• Normally Closed (NC): Circuit is closed when the float is at rest (low level).
• Normally Open (NO): Circuit is open when the float is at rest (low level).

1. Identify the Contacts: Determine the COM, NC, and NO contacts on the float switch.
2. Connect Power: Attach the COM contact to the power supply.
3. Set Up Control Circuit: Connect the NO or NC contact to the device you wish to control (e.g., a relay or an alarm).
4. Mount the Float Switch: Secure the float switch at the desired height in the tank or container.
5. Test the System: Fill the container with liquid to ensure the float switch activates at the correct level.

• Mounting Position: Ensure the float switch is mounted vertically for accurate operation.
• Material Compatibility: Choose a float switch with materials compatible with the liquid.
• Electrical Ratings: Do not exceed the voltage and current ratings of the float switch.
• Debouncing: Implement a debounce circuit or software to prevent rapid switching due to turbulence.

• Switch Does Not Activate: Verify the float can move freely and is not obstructed.
• Intermittent Operation: Check for loose connections and ensure proper contact with terminals.
• Corrosion or Damage: Inspect the float switch for any signs of wear or chemical damage.

• Free Movement: Regularly check that the float moves without hindrance.
• Secure Connections: Tighten terminal screws and ensure wires are firmly connected.
• Regular Inspection: Periodically inspect the float switch for any signs of damage or malfunction.

Q: Can I use a float switch with any liquid? A: Float switches are designed for use with a variety of liquids, but always check the material compatibility with the specific liquid in your application.

Q: How do I adjust the switch activation point? A: Adjust the mounting height of the float switch to change the activation point.

Q: Is it possible to use a float switch with an Arduino? A: Yes, a float switch can be connected to an Arduino's digital input pin for liquid level sensing.

// Define the float switch pin
const int floatSwitchPin = 2;

void setup() {
  pinMode(floatSwitchPin, INPUT_PULLUP); // Set the float switch pin as an input
  Serial.begin(9600);                    // Start serial communication
}

void loop() {
  // Read the state of the float switch
  int floatSwitchState = digitalRead(floatSwitchPin);

  // Check if the float switch is triggered (assuming NO configuration)
  if (floatSwitchState == LOW) {
    // The liquid level has reached the float switch
    Serial.println("Liquid level high");
  } else {
    // The liquid level is below the float switch
    Serial.println("Liquid level low");
  }

  delay(1000); // Wait for 1 second before reading again
}

Note: The above code assumes the float switch is wired in a Normally Open (NO) configuration. If your switch is Normally Closed (NC), the logic in the if statement will be reversed.