KY-050 Ultrasonic distance sensor

This module is ideal for distance measurement in a range between 2 cm and 3 m. With a resolution of around 3 mm, distances can be measured precisely using an ultrasonic signal. When a signal (falling edge) is applied to the trigger input, the sensor starts a distance measurement. The result is output at the echo output as a PWM TTL signal.

The ultrasonic distance sensor is particularly useful for obstacle detection, distance measurement, level indicators and various industrial applications. Thanks to its high precision and fast response time (minimum time between measurements is 50 µs), the sensor can operate reliably in real time.

This module is versatile and offers a simple and effective solution for projects where accurate distance measurements are required.

Principle of operation

This module shows how an ultrasonic loudspeaker and a microphone can be used to measure the distance to an object without contact. The principle is based on the fact that the speed of sound in air remains almost constant at constant temperature - at 20 °C it is 343.2 m / s.

From this, the distance measurement can be converted into a time measurement, which can then easily be taken over by microcontrollers.

When triggered, the ultrasonic loudspeaker (transducer) emits an ultrasonic noise of maximum 200µs. The ultrasonic loudspeaker emits a 40 kHz signal. This means that 8 periods (edge changes) are emitted within the 200µs in which the sensor emits its ultrasonic noise. In order to arrive at these 8 periods of the 40 kHz signal mathematically, one calculates the whole thing as shown in the following.

Number of periods in one second = 40000
Time = 1s
Duration of a single period:
1s / 40000 = 25µs**

Maximum length of ultrasonic sound = 200us
Duration of a single period = 25us
Number of periods in ultrasonic sound:
200µs / 25µs = 8

The principle is kept simple, an ultrasonic sound is emitted from the speaker on the PCB, which is then reflected from an object and picked up by the microphone on the PCB. Ultrasound is used because it is outside the hearing range of the human ear (about 20Hz-22kHz).

Transmission of the ultrasonic signal is started when a 10µs long start signal (ActiveHigh) is received at the "Trigger input pin". After transmission, the signal is activated at the "Echo output signal pin" (ActiveHigh). If the reflected signal is now picked up again at the microphone, the echo signal is deactivated again after detection. The time between activation and deactivation of the echo signal can be measured and converted to distance, as this also corresponds to how long it takes the ultrasonic signal to cover the distance between loudspeaker-> reflecting wall -> microphone in the air. The conversion is then made by approximating a constant air velocity - the distance is then half the distance traveled.

Pin assignment

Code example

The example program activates the distance measurement according to the above principle and measures the time until the ultrasonic signal is picked up by the microphone with the help of the Arduino function pulseIn . This time is then taken as the basis for the conversion of the distance - the result is then output in the serial output. If the signal is outside the measuring range, a corresponding error message is output.

To load the following code example onto your Arduino, we recommend using the Arduino IDE. In the IDE, you can select the appropriate port and board for your device.

Copy the code below into your IDE. To upload the code to your Arduino, simply click on the upload button.

#define echoPin 7 // Echo input pin
#define triggerPin 8 // Trigger output pin
 
// Required variables are defined
int maximumRange = 300; 
int minimumRange = 2; 
long distance;
long duration;
 
void setup() {
  pinMode(triggerPin, OUTPUT);
  pinMode(echoPin, INPUT);
  Serial.begin(9600);
  Serial.println("KY-050 Distance measurement");
}
 
void loop() {
  // Distance measurement is started using the 10us trigger signal
  digitalWrite(triggerPin, HIGH);
  delayMicroseconds(10); 
  digitalWrite(triggerPin, LOW);

  // Now wait at the echo input until the signal has been activated
  // and then the time is measured to see how long it remains activated 
  duration = pulseIn(echoPin, HIGH);

  // Now the distance is calculated using the recorded time
  distance = duration/58.2;

  // Check whether the measured value is within the permissible distance
  if (distance >= maximumRange || distance <= minimumRange) {
    // If not, an error message is displayed.
    Serial.println("Distance outside the measuring range");
    Serial.println("-----------------------------------");
  }  
  else {
    // The calculated distance is output in the serial output
    Serial.print("The distance is: ");
    Serial.print(distance);
    Serial.println(" cm");
    Serial.println("-----------------------------------");
  }
  // Pause between the individual measurements
  delay(500);
}