Planet Arduino

While you might think of radar pointing toward the skies, applications for radar have found their way underground as well. Ground-penetrating radar (GPR) is a tool that sends signals into the earth and measures their return to make determinations about what’s buried underground in much the same way that distant aircraft can be located or identified by looking for radar reflections. This technology can also be built with a few common items now for a relatively small cost.

This is a project from [Mirel] who built the system around a Arduino Mega 2560 and antipodal Vivaldi antennas, a type of directional antenna. Everything is mounted into a small cart that can be rolled along the ground. A switch attached to the wheels triggers the radar at regular intervals as it rolls, and the radar emits a signal and listens to reflections at each point. It operates at a frequency range from 323 MHz to 910 MHz, and a small graph of what it “sees” is displayed on an LCD screen that is paired to the Arduino.

Using this tool allows you to see different densities of materials located underground, as well as their depths. This can be very handy when starting a large excavation project, detecting rock layers or underground utilities before digging. [Mirel] made all of the hardware and software open-source for this project, and if you’d like to see another take on GPR then head over to this project which involves a lot of technical discussion on how it works.

Full-size metal detectors are great for narrowing down a region to start digging through. But what if you had a smaller metal detector that could pinpoint the location? Then you could spend far less time digging and way more time sweeping for metal.

Metal detectors work because of the way metal behaves around electromagnetic fields. [mircemk] reused the ferrite core from an old MW radio to build the antenna coils. When metal objects are close enough, the induced electromagnetism changes the frequency, and the Arduino blinks an LED and beeps a buzzer in time with the new frequency.

[mircemk]’s handheld metal detector is quite sensitive, especially to smaller objects. As you can see in the demo video after the break, it can sense coins from about 4cm away, larger objects like lids from about 7 cm, and tiny things like needles from a few millimeters away. There’s also an LED for treasure hunting in low light.

Don’t want to pinpoint a bunch of useless junk? Build in some phase detection to help you discriminate.

Ever wanted to own your own Theremin but couldn’t justify dropping hundreds of dollars on one? Now you can build your own, or buy it for a quintuplet of Hamiltons. The Open.Theremin.UNO project has built up antenna-based oscillator control around the ubiquitous Arduino Uno board.

So what’s the Arduino in there for? This is a digital Theremin, but check out the video below and you’ll agree that it sounds amazing and has excellent response. The aluminum antennas used for volume and pitch are attached to the top portion of the shield but it sounds like they’re not included in the kit. Don’t fret, you can use a variety of materials for this purpose. On the bottom you need to connect a speaker cable, and also a ground wire if that cable’s not grounded.

As the name implies, this is Open Hardware and we’re quite happy with the documentation on their site and the BOM (found on the GitHub repo). This design was shown off back in 2013 hiding in a pack of cigarettes. If you don’t want to build your own they’re selling kits on their site for 48 Euro delivered, or on Tindie for $55.

Okay, we’ve screwed this up so many times that we’re going to try to get it right here: the Theremin was not heard in the opening of Star Trek the original series, or in the opening of Doctor Who. It wasn’t featured in “Good Vibrations” either. As far as we can tell, it’s not used for anything in pop culture at all… but recognizing the sound and knowing what one is remains core geek knowledge.

If you want a Theremin to play using your entire body you need the Theremin Terpsitone.

[via Open Electronics]