In a world of always-connected devices and 24/7 access to email and various social media and messaging platforms, it’s sometimes a good idea to take a step away from the hustle and bustle for peace of mind. But not too big of a step. After all, we sometimes need some limited contact with other humans, so that’s what [EverestX] set out to do with his modern, pocket-sized communication device based on pager technology from days of yore.

The device uses the POCSAG communications protocol, a current standard for pager communications that allows for an SMS-like experience for those still who still need (or want) to use pagers. [EverestX] was able to adapt some preexisting code and port it to an Atmel 32u4 microcontroller. With a custom PCB, small battery, an antenna, and some incredibly refined soldering skills, he was able to put together this build with an incredibly small footprint, slightly larger than a bottle cap.

Once added to a custom case, [EverestX] has an excellent platform for sending pager messages to all of his friends and can avoid any dreaded voice conversations. Pager hacks have been a favorite around these parts for years, and are still a viable option for modern communications needs despite also being a nostalgic relic of decades past. As an added bonus, the 32u4 microcontroller has some interesting non-pager features that you might want to check out as well.

Thanks to [ch0l0man] for the tip!

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.

We are continuously inspired by our readers which is why we share what we love, and that inspiration flows both ways. [jetpilot305] connected a Rothult unit to the Arduino IDE in response to Ripping up a Rothult. Consider us flattered. There are several factors at play here. One, the Arduino banner covers a lot of programmable hardware, and it is a powerful tool in a hardware hacker’s belt. Two, someone saw a tool they wanted to control and made it happen. Three, it’s a piece of (minimal) security hardware, but who knows where that can scale. The secure is made accessible.

The Github upload instructions are illustrated, and you know we appreciate documentation. There are a couple of tables for the controller pins and header for your convenience. You will be compiling your sketch in Arduino’s IDE, but uploading through ST-Link across some wires you will have to solder. We are in advanced territory now, but keep this inspiration train going and drop us a tip to share something you make with this miniature deadbolt.

Locks and security are our bread and butter, so enjoy some physical key appreciation and digital lock love.