Ultrasonic Sonar Detects Hidden Objects

While early scientists and inventors famously underestimated the value of radar, through the lens of history we can see how useful it became. Even though radar uses electromagnetic waves to detect objects, the same principle has been used with other propagating waves, most often sound waves. While a well-known use of this is sonar, ultrasonic sensors can also be put to use to make a radar-like system.

This ultrasonic radar project is from [mircemk] who uses a small ultrasonic distance sensor attached to a rotating platform. A motor rotates it around a 180-degree field-of-view and an Arduino takes and records measurements during its trip. It interfaces with an application running on a computer which shows the data in real-time and maps out the location of all of the objects around the sensor. With some upgrades to the code, [mircemk] is also able to extrapolate objects hidden behind other objects as well.

While the ultrasonic sensor used in this project has a range of about a meter, there’s no reason that this principle couldn’t be used for other range-finding devices to extend its working distance. The project is similar to others we’ve seen occasionally before, but the upgrade to the software to allow it to “see” around solid objects is an equally solid upgrade.

14 thoughts on “Ultrasonic Sonar Detects Hidden Objects

  1. I made a similar project a few years back but couldn’t get any useful data due to the propensity of everyday objects to attenuate and scatter ultrasound.

    Regarding the Radar comparison surely Sonar is a better fit?

    1. Probably, but this is a simple project with an EUR2 stepper motor and an EUR3 ultrasonic detector.

      If you want to do this with reflected phase, then you need a whole array of sensors, better amplification of the return signal (for each sensor) and a lot more math on a beefy microcontroller to make sense of it all.

      I am surprised about the short range. Range is very much dependent on the size and the material of the object. Hard objects such as a steel frying pan can be detected from greater distances then fluffy objects such as woolen sweater.
      But several meters should be doable with these sensors. A possible cause is that vibrations introduced by the steppermotor interfere with the receiver and reduce it’s sensitivity. However, in that case I would also expect lots of false readings. Does range improve when the motor is stationary?

    1. For large scale geology they do something similar, usually setting off an explosive charge and analyzing the shock waves bouncing off features under the ground.

      For something small, it would depend on ground composition, and would likely be limited in range/effectiveness. Ultrasound can be used to image inside concrete, but the more voids in the material, the less effective the results. For “seeing” underground (e.g. see buried things, pipes, treasure, lost cities,etc) the current preferred way is Ground Penetrating Radar.

      1. “For large scale geology they do something similar, usually setting off an explosive charge and analyzing the shock waves bouncing off features under the ground.”

        But in most of those cases, it is infrasonic.

  2. FFT makes miracles but would it be first choice to remove “hidden” object after one swip of “radar” as a proof of concept?
    Blue dots trace could be echos, phase shifts, ghosts…

  3. The most interesting thing about this hack is the soldering and breaking out of the ‘raw echo’ pin on the ultrasonic module. It is misleading to say it can detect objects ‘hidden’ behind other objects, it is perhaps more accurate to say that you can listen for a second echo after the first is received which can give information about a further object further away.

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