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Gyroscopes and giants Techno Talk From origami-inspired circuits to dungeon-delving inertial sensors, join me on an adventure where ancient folding arts, cutting-edge gyroscopes and underground navigation all collide in unexpectedly entertaining ways. Do you remember Up Pompeii!, the classic British TV comedy that aired in 1969 & 1970, starring Frankie Howerd as the ever-scheming Lurcio? One of the best-remembered running gags was Frankie’s parody of an old vaudeville line when he said, “A funny thing happened to me on the way to Colosseum”. The reason this popped into (what I laughingly call) my mind is that something funny happened to me the other day. I was at home, ensconced in my comfy chair, happily reading my copy of the October 2025 issue of Practical Electronics, which had finally managed to wend its way across the pond to me here in America. I’d just begun to peruse my Techno Talk column (by the time the magazine reaches me, I have usually forgotten what I wrote about). “Hey”, said my wife (Gigi the Gorgeous), “there’s a picture of some bone conduction headphones like yours in the magazine you’re reading”. I had to laugh. “These are my headphones”, I replied. “I wrote this article!” I’d like to say she was impressed, but… moving on… Origami, kirigami and circuits Life is a funny old thing when you come to think about it. Back in the mists of time, when dinosaurs ruled the Earth and I was in high school, it never occurred to me that one of my chums would one day grow up to become a world-renowned origami grandmaster, but such is indeed the case. My friend, whom we will call Nick (because that’s his name), has written more than 100 books on the art of origami (nickorigami.com). The reason I mention this here is that I recently came across an interesting article describing how researchers are exploring traditional Japanese paper folding (origami) and paper cutting (kirigami) techniques to create kiriorigami printed circuit structures (https://pemag.au/link/ac8t). On a somewhat related note, I also ran across a column describing how scientists have developed what they describe as a “photonic origami” method of producing tiny glass structures (https://pemag.au/link/ac8u). Apparently, this accidental discovery could revolutionise computing, cameras and sensors. Speaking of sensors… Sophisticated sensors I love the incredible, advanced sensors that are available to us these days. When I started out in electronics as a Max the Magnificent 12-year-old in 1969, the best I could hope to lay my hands on were items like magnetic reed switches, mercury tilt switches and light-dependent resistors (LDRs). Today, you can purchase a cheapand-cheerful breakout board (BoB) featuring a teeny-tiny chip that boasts a 32-bit microcontroller along with a micro-electromechanical system (MEMS) that provides a 3-axis accelerometer, a 3-axis gyroscope and a 3-axis magnetometer. A 3-axis accelerometer can measure linear acceleration (change in velocity) in the X (forward-back), Y (left-right), and Z (up-down) axes. Meanwhile, a three-axis gyroscope can measure angular velocity (how fast something is rotating) around the X (roll), Y (pitch), and Z (yaw) axes. A magnetometer measures magnetic fields and can be used like a 3D compass. Each of these devices has shortcomings when used alone: accelerometers have a noisy output and can’t distinguish between tilt and linear motion, gyroscopes provide smooth shortterm data but suffer from drift that accumulates over time, and magnetometers offer absolute heading but are easily disturbed by local magnetic fields. This is where the microcontroller comes in. By applying sensor fusion algorithms, the strengths of each technology can be used to compensate for the weaknesses of the others. A 9-DoF IMU board. Source: Adafruit. Kirigami is similar to origami except that the paper may be cut and glued. 36 Practical Electronics | December | 2025 Techno Talk Max the Magnificent Going down… As wonderful as the aforementioned sensors are, before using them, you need to establish a starting point from which all subsequent measurements will be made. Suppose you were poised to enter one of the world’s deepest mines, for example. You would probably begin by establishing your precise location using one or more global navigation satellite systems (GNSSs). Examples of currently available GNSSs include GPS (developed by the USA), GLONASS (developed by Russia), Galileo (developed by the European Union), and Beidou (developed by China). Once you’d entered the mine and transitioned into a GNSS-denied state, you might switch over to some form of inertial navigation system (INS). This INS would employ an inertial measurement unit (IMU) to estimate your current position, velocity, and orientation without relying on external references. It’s the IMU that would contain the accelerometers, gyroscopes and magnetometers. The idea is that you could travel all the way down to the bottom of the mine, and subsequently return to the surface, while always understanding exactly where you were and in what direction you were pointing. Once again, however, this depends on knowing your starting point. Fortunately, the lights are on; otherwise, you really would be in a pickle. Tunnel entrances are all around the cavern. There’s also a note that says, “Take the tunnel heading north (all the others lead to certain death)”. There’s an IMU next to you, but it’s powered down, meaning it has lost track of its current position and orientation. Even worse, when you look inside, you discover that some scamp has removed its magnetometer. However, even if the magnetometer were still present, you would be foolish to rely on it because mines often contain large amounts of ferromagnetic material that distort the Earth’s magnetic field and cause local anomalies, making readings unreliable. Worst of all, you are starting to feel a little peckish. What are you going to do? 21st-century gyroscopes Well, if you are in possession of a Boreas IMU from the Australian company Advanced Navigation (https://pemag.au/link/ac8v), you’re in luck, because this bodacious beauty boasts three-axis cuttingedge digital fibre-optic gyroscope (DFOG) technology. The DFOGs used in Boreas IMUs are so sensitive that they can detect the Earth’s rotation, which is 15° per hour. This means several things. First, these are the only gyroscopes on the planet that don’t suffer from significant drift. Secondly, it knows which way it’s pointing, even when deep underground. This means you can quickly identify the exit tunnel in our D&D scenario and head home for a well-deserved bacon sandwich. Recently, when I was chatting with the folks at Advanced Navigation, they told me that they had used their DFOG technology to demonstrate a breakthrough in underground navigation—delivering high-precision positioning without reliance on fixed infrastructure or GNSS. This was demonstrated in one of the world’s deepest underground mines at Pyhäjärvi, Finland, shown in the photograph below. So, from optical origami to fibre-­ optic gyros, who can say which curious contraptions tomorrow will bring? As for me, I’ll settle for an IMU that can guide me safely to the fridge—and back again before PE Gigi notices. Dungeons & Dragons Let’s flip everything around a bit. Imagine that the following text is being read out in the dulcet tones of James Earl Jones, pretending to be the Dungeon Master in a game of Dungeons & Dragons (D&D): You wake up and find yourself in a huge cavern at the bottom of one of the world’s deepest mines. The Pyhäsalmi Mine in Pyhäjärvi, Finland. Source: Advanced Navigation. Practical Electronics | December | 2025 37