How to Use ajsr04: Examples, Pinouts, and Specs

The AJSR04 is an ultrasonic distance sensor designed to measure distances by emitting ultrasonic waves and calculating the time it takes for the echo to return. This sensor is widely used in robotics, automation, and IoT applications for tasks such as obstacle detection, distance measurement, and object tracking. Its compact design and reliable performance make it a popular choice for both hobbyists and professionals.

• Obstacle detection in robotics
• Distance measurement in automation systems
• Parking assistance systems
• Liquid level measurement
• Proximity sensing in IoT devices

The AJSR04 sensor operates by sending ultrasonic pulses at a frequency of 40 kHz and measuring the time it takes for the echo to return. Below are the key technical details:

The AJSR04 has four pins, as described in the table below:

1. Power Supply: Connect the VCC pin to a 5V DC power source and the GND pin to ground.
2. Trigger Signal: Use a microcontroller (e.g., Arduino) to send a 10 µs TTL pulse to the Trig pin.
3. Echo Signal: Read the Echo pin to measure the duration of the returned pulse. The duration is proportional to the distance of the object.

The distance can be calculated using the formula: [ \text{Distance (cm)} = \frac{\text{Pulse Duration (µs)}}{58} ] This formula accounts for the speed of sound in air (approximately 343 m/s).

Below is an example Arduino sketch to measure distance using the AJSR04:

// Define pins for the AJSR04 sensor
const int trigPin = 9; // Trigger pin connected to digital pin 9
const int echoPin = 10; // Echo pin connected to digital pin 10

void setup() {
  pinMode(trigPin, OUTPUT); // Set the trigger pin as an output
  pinMode(echoPin, INPUT);  // Set the echo pin as an input
  Serial.begin(9600);       // Initialize serial communication at 9600 baud
}

void loop() {
  // Send a 10 µs pulse to the Trig pin
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);

  // Measure the duration of the pulse on the Echo pin
  long duration = pulseIn(echoPin, HIGH);

  // Calculate the distance in cm
  float distance = duration / 58.0;

  // Print the distance to the Serial Monitor
  Serial.print("Distance: ");
  Serial.print(distance);
  Serial.println(" cm");

  delay(500); // Wait for 500 ms before the next measurement
}

• Ensure the sensor is mounted securely to avoid vibrations that may affect accuracy.
• Avoid placing the sensor near ultrasonic noise sources, such as other ultrasonic sensors or motors.
• Use a decoupling capacitor (e.g., 10 µF) across the VCC and GND pins to stabilize the power supply.

1. No Output from Echo Pin

   • Cause: The Trig pin is not receiving a proper 10 µs pulse.
   • Solution: Verify the microcontroller code and ensure the Trig pin is correctly connected.

2. Inaccurate Distance Measurements

   • Cause: Interference from nearby objects or incorrect formula usage.
   • Solution: Ensure the sensor has a clear line of sight to the target object and use the correct distance formula.

3. Sensor Not Responding

   • Cause: Insufficient power supply or loose connections.
   • Solution: Check the power supply voltage and ensure all connections are secure.

Q: Can the AJSR04 detect transparent objects?
A: The AJSR04 may struggle to detect transparent objects like glass due to poor ultrasonic wave reflection.

Q: What is the maximum range of the AJSR04?
A: The maximum range is 400 cm (4 meters), but accuracy may decrease at longer distances.

Q: Can I use the AJSR04 with a 3.3V microcontroller?
A: The AJSR04 requires a 5V power supply, but the Trig and Echo pins can often be interfaced with 3.3V logic using a level shifter.

By following this documentation, users can effectively integrate the AJSR04 ultrasonic sensor into their projects for reliable distance measurement and obstacle detection.