How to Use Pololu Distance Sensor with Pulse Width Output, 300cm Max: Examples, Pinouts, and Specs

The Pololu Distance Sensor with Pulse Width Output (Manufacturer Part ID: 4079) is a high-performance distance measuring sensor designed for applications requiring accurate distance readings up to 300 cm. This sensor uses pulse width modulation (PWM) to output distance measurements, making it easy to interface with microcontrollers and other digital systems. Its compact size and reliable performance make it ideal for robotics, automation, and object detection systems.

• Obstacle detection in robotics
• Automated guided vehicles (AGVs)
• Proximity sensing in industrial automation
• Distance measurement in smart home devices
• Object tracking and collision avoidance systems

1. Power the Sensor: Connect the VIN pin to a 5V power source and the GND pin to the ground of your circuit.
2. Read the PWM Output: Connect the PWM OUT pin to a digital input pin of your microcontroller. The pulse width of the signal corresponds to the measured distance.
3. Convert Pulse Width to Distance: Measure the duration of the high pulse on the PWM OUT pin. Use the formula below to calculate the distance: [ \text{Distance (cm)} = \text{Pulse Width (ms)} \times 10 ] For example, a pulse width of 15 ms corresponds to a distance of 150 cm.

• Power Supply: Ensure a stable 5V power supply to avoid inaccurate readings.
• Interference: Avoid placing the sensor near reflective surfaces or strong light sources, as these may affect accuracy.
• Mounting: Position the sensor so that it has a clear line of sight to the target object.
• Signal Filtering: If the PWM signal is noisy, consider adding a capacitor between the PWM OUT pin and ground to stabilize the output.

The following Arduino code demonstrates how to read the PWM output from the sensor and calculate the distance:

// Define the pin connected to the PWM OUT of the sensor
const int pwmPin = 2;

void setup() {
  // Initialize serial communication for debugging
  Serial.begin(9600);
  
  // Set the PWM pin as an input
  pinMode(pwmPin, INPUT);
}

void loop() {
  // Measure the duration of the HIGH pulse on the PWM pin
  unsigned long pulseWidth = pulseIn(pwmPin, HIGH);
  
  // Convert the pulse width to distance in cm
  float distance = pulseWidth * 0.1; // 1 ms = 10 cm
  
  // Print the distance to the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");
  
  // Add a small delay for stability
  delay(100);
}

1. No Output Signal

   • Cause: The sensor is not powered correctly.
   • Solution: Verify that the VIN pin is connected to a 5V power source and the GND pin is connected to ground.

2. Inaccurate Distance Readings

   • Cause: Interference from reflective surfaces or strong light sources.
   • Solution: Reposition the sensor to avoid interference and ensure a clear line of sight to the target.

3. PWM Signal is Unstable

   • Cause: Electrical noise in the circuit.
   • Solution: Add a decoupling capacitor (e.g., 0.1 µF) between the PWM OUT pin and ground.

4. Distance Readings are Stuck at Maximum or Minimum

   • Cause: The target object is out of the sensor's range.
   • Solution: Ensure the object is within the 5 cm to 300 cm range.

Q: Can this sensor detect transparent objects?
A: The sensor may have difficulty detecting transparent or highly reflective objects. For best results, use opaque and matte surfaces.

Q: How fast can the sensor update distance readings?
A: The sensor provides a new distance reading approximately every 50 ms.

Q: Can I use this sensor with a 3.3V microcontroller?
A: The sensor requires a 5V power supply, but the PWM output can be read by 3.3V logic microcontrollers. Use a level shifter if needed.

Q: What is the accuracy of the sensor?
A: The sensor provides reliable readings with an accuracy of ±5% under ideal conditions.