Here is how the LEGO ultrasonic sensor works:
The LEGO ultrasonic sensor determines the distance to an object by emitting high-frequency sound waves and measuring the time it takes for those waves to return after bouncing off the object.
The process relies on the principle of echolocation, similar to how bats navigate or sonar systems function.
Sending Sound Waves
The sensor has a transducer that acts as a speaker, sending out short bursts of sound waves. A key feature is that these sound waves are ultrasonic, meaning their frequency is too high for you to hear.
Receiving Reflected Sound
After sending out the sound pulse, the sensor switches modes. It now listens for the echo – the sound waves that have bounced off an object and are returning. The same transducer often acts as a microphone, detecting these returning waves.
Measuring Time of Flight
The sensor precisely measures the time it takes for the sound to reflect back to the sensor from the moment it was sent out. This time is known as the "time of flight."
Calculating Distance
Since the speed of sound in air is relatively constant (though slightly affected by temperature and humidity), the sensor can calculate the distance to the object using the measured time of flight. A shorter time means the object is closer, and a longer time means it's farther away. The sensor performs this calculation internally.
The distance can then be reported by the sensor in either inches or centimetres.
Here's a simple overview:
| Step | Action |
|---|---|
| 1. Emit Sound | Sends out ultrasonic waves. |
| 2. Listen for Echo | Waits for returning waves. |
| 3. Measure Time | Records time for sound to return. |
| 4. Calculate Distance | Uses time to find distance. |
This process allows your LEGO robot to "see" objects and obstacles in its path, enabling it to navigate, avoid collisions, or interact with its environment based on proximity.
