Bert writes – “The Devantech SFR04 Ultrasonic Range Finder indicates the distance to the closest object within range. Echo’s that arrive later are received and processed, but subsequently ignored. For a true radar all signals should be taken into account. So, time to heat up the old soldering iron and make some modifications to the Devantech SFR04 circuit board.” [via] – Link.
DIY Ultrasonic sonar with LEGOs