LEGO MINDSTORMS Robot Inventor
Radar
This model radar rotates the distance sensor slowly around in a circle to looks for targets (although real radar uses radio waves not ultrasonic sound waves). It will beep when it sees each target and plot a pixel on the display to map its location.
Building Instructions
Radar
Targets
Using the Radar Programs
The ultrasonic sensor is not very precise, has a wide field of "view", and can be finicky, so try these things when running the programs:
Place the radar in the center of a room as far away from walls and other things as possible.
Place targets at a distance ranging from about 10 - 50 cm (4 - 20 inches) from the radar.
Make the flat plate of the target exactly perpendicular to the angle of view of the sensor. If the plate is at an angle, the sound waves bounce away to the side and are not detected.
Targets that are too close together will be detected as a single target. Start with the two targets separated by at least 90 degrees of sensor rotation.
When running the "Radar Plot" program, make sure the sensor starts aligned properly with the hub (see building instructions), so that the pixels will be plotted at the correct angles.
The "Radar Beep" program uses a simple sensor event to trigger the beeps. This is very easy but has some weaknesses. The "Radar Plot" progam improves on it somewhat by using more complex logic and variables. The logic tracks when each object is first seen, is getting closer, and when it passes the closest point and starts to get farther away. In addition to trying to separate multiple targets a little better, this allows it to map the closest point of the object, whereas the "Radar Beep" program just beeps as soon as the beginning of the object is seen.