on Event

Run some code when an object is detected by the ultrasonic sensor.

sensors.ultrasonic1.onEvent(UltrasonicSensorEvent.ObjectDetected, function () {


How an object is detected depends on the distance and movement thresholds set for the sensor. A threshold is a number that is some distance in centimeters or the strength of ultrasonic sound. You can set a distance to detect something that is far, near, or is sending out ultrasound (like the sensor of another robot in the area). The two thresholds you can set are:

  • near: a distance to set to detect objects coming close
  • detected: the strength of ultrasound to needed to detect presence of another ultrasonic sensor

Both near and far have distance thresholds set in centimeters. The detect threshold is a value of strength the ultrasonic sound in decibels.


  • event: the object detection action to wait for. The detection types (events) are:
    • object detected: the detected something that moved
    • object near: the sensor detected something within the distance of the near threshold
  • handler: the code you want to run when something is dectected by the ultrasonic sensor.


When the ultrasonic sensor on port 4 detects a near object, display its distance on the screen.

sensors.ultrasonic4.onEvent(UltrasonicSensorEvent.ObjectNear, function () {
    brick.showString("Object detected at:", 1)
    brick.showNumber(sensors.ultrasonic4.distance(), 2)
    brick.showString("centimeters", 3)

See also

pause until