Obstacle Avoidance Glossary

Quick definitions for the core terms used in this session.

sensor: A part that measures something about the world — like how far away an object is — and reports it back to your code as a number.

UltrasonicSensor: The Pybricks tool for the distance (“eyes”) sensor. It sends out sound you can’t hear and times the echo to figure out how far away something is.

distance: What eyes.distance() gives you — how far the nearest thing is, in millimeters. It returns 2000 mm when nothing is detected (the “no object” reading).

if: A decision in code. “If something is close, do this.” The robot only runs the if block when the condition is true.

else: The other choice. “…else (otherwise), do this instead.” The robot runs the else block when the if condition is false.

condition: The true-or-false test an if checks, like eyes.distance() < 200 (“is the distance less than 200?”). The answer decides which block runs.

while loop: A loop that keeps repeating as long as its condition is true. while True: is always true, so it repeats forever — perfect for checking a sensor over and over. Stop it with the editor’s Stop button.

wait: A short pause, in milliseconds. wait(10) waits 10 ms so the loop doesn’t race ahead faster than the robot can react.

DriveBase: The Pybricks tool that controls both drive motors together. Carried over from earlier sessions — here we also use robot.drive(speed, turn) to keep moving continuously while we watch the sensor.

millimeter (mm): The unit the distance sensor uses. 1000 mm = 1 meter. A new pencil is about 190 mm long.

trigger distance: The number you compare the sensor reading against to decide “too close.” You measure and adjust it on the real course — it’s a calibration value, not a fixed number.

bug: When the robot does something you didn’t want. It’s not a mystery — it’s sensor data: the robot did exactly what the code said. Read the code to find what you actually told it to do.