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An Open Source Linear Capacitive Encoder

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If you’ve ever pulled apart a set of digital calipers, you’ve probably marvelled at the capacitive encoder that does all the measuring work. There’s nothing stopping you from using the same techniques yourself, as [Nick] demonstrates with an open-source capacitive encoder of his own design. The sensor PCB works by by having a grid of eight transmitting antennas, etched into a PCB, beneath a larger receiving antenna. The transmitting antennas pulse out a pattern as the sensor PCB moves, with the signals bouncing back from the reflector PCB which is fixed in place. The varying capacitance caused by the position of the reflector elements relative to the sensor PCB varies the strength of the pulses hitting the receiving antenna. A microcontroller—in this case an STM32—can read those pulses to determine the displacement of the sensor PCB relative to the reflector down to a very fine degree. In this case, to an accuracy of 40 micrometers. Not bad! If you need ultra-fine li...

Keeping Old Wi-Fi Radios Alive With Stream Conversion

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There are plenty of Wi-Fi radios out there that were built over the last two decades or so. However, many older models are now becoming less useful because many internet radio stations are switching to newer streaming formats that they don’t support. [Clifford Farrugia] has been working on a little project to save these appliances from the e-waste bin. The HLS Radio Converter is the result of that work. It’s a small open-source tool that converts modern HTTP Live Streaming (HLS) protocol streams into regular old HTTP MP3 streams that older internet radio appliances are built to decode. You can run the tool on something as simple as an old Raspberry Pi. To make it work, you just give the tool the URL of the stream you’re looking to convert, and it then spits out a new URL to point your radio to which has the stream in the old-school format instead. It’s a simple tool, but one that should prove very useful if you have a beloved old internet radio that can’t...

Making a Five-Segment Display with Platinum-Titanium Cathodes

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Before the advent of effective semiconductor LEDs many display types existed to display things like numbers and other characters. The Nixie tube is a well-known one, along with VFDs and there are also lesser known ones such as Burrough’s Panaplex, which all saw plentiful use in everything from calculators to audio equipment. The design that [Witchcraft and Alchemy] made appears to lean heavily on this Panaplex design. Rather than neon, this uses argon as the gas. The anode is formed by the indium-tin oxide layer on a piece of glass, with the cathode sputtered onto the other side in the form of first a titanium layer followed by platinum. This combination helps to prevent the latter from flaking off due to incompatibilities between the molecular matrices of the glass and platinum. Since this is an early prototype, only five segments were sputtered onto the glass and driven with a 74141 Nixie driver IC, creating the expected purple glow in a vacuum chamber. Following this a self-...

Every Type of Current Sensor Explained

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Measuring electric currents is an essential element of many electrical systems, but doing so in a way that is as nonintrusive as possible is not an easy problem to solve. Due to this we got a wide variety of current sensors to choose from for any given application, with [ElectrArc240] running us through these variants in a recent video. The fairly low-tech, cheap and quite reliable method of using a shunt resistor is first demonstrated. This sees a lot of use in fairly low-voltage and low-current applications, with for example videocards using it to limit the amount of power the GPU can use, a feature that modders will happily bypass. Here simply the voltage drop across a known resistance value is measured, from which the current can be derived. Of course, you got higher voltage and higher current applications too, as well as direct- and alternating current, with the latter especially allowing for easy current measurements simply from the electromagnetic field, or flux. Anyone who h...

Sega Genesis Controllers on the Philips CD-i

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The Philips CD-i was not popular upon its launch in 1991, and is barely acknowledged today. In the opinion of [MattKC], it had a particularly poor selection of controllers, too, and it’s often hard to find used examples anyway. To rectify this situation, he whipped up an adapter to let him use Sega Genesis controllers instead. The benefit of the Genesis controller is that it uses DB-9 connectors that are readily available, and it’s got a simple pinout that is compatible with the Atari joystick port, too. It makes interfacing the controllers supremely easy. Converting the controllers required using a Arduino Pro Micro to read the Genesis pad and translate it into something suitable for the CD-i. On the Sega controller side, the microcontroller just has to strobe one pin while reading the state of others to determine what all the buttons are doing. The CD-i, however, expects a serial data stream from the original Philips controllers. Thus, the microcontroller is set up to po...

Knitting Yarn and Filament with FilaLoom

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We don’t generally think of 3D printing and knitting in the same sentence. One uses threads and fine motor control, while the other requires great knowledge of pressing buttons and plastics. That said, they both entail stacking material over and over until a finished product emerges. So why not blend the two crafts together? [Joram de Haas] decided to work on just that in the form of FilaLoom . 2D, 3D, and even embedded mechanisms! This isn’t the first time we have seen additional elements embedded into 3D printed parts here on Hackaday. However, this particular implementation has some extra features which allow the embedded structures to grow larger than most examples prior. Instead of placing any implements directly into a structure by hand, all thread is placed by a tool head not so different from tool-changer printers. Using both the 3D printing tool head and the thread tool, some truly interesting properties can emerge from the finished product. If you aren’t interested in...

Using Ultrasound and Microbubbles to Make Tiny Devices

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Although we generally do not look at bubbles in fluids as more than a curiosity – if not an outright annoyance – in certain contexts they can be very useful. If you can namely control their formation and position, you can use them in small systems to control actuators and dynamically affect acoustic systems. The main issues here are that controlling their formation, lifetime and controllability remain hard to solve. This is what [Zhiyuan Zhang] et al. sought to address, with a recent study published in  Science Advances covering their approach using ultrasound-driven, electronically programmable microbubbles. There’s also a Cornell press release article about their findings, which uses a new device that produces hydrogen bubbles along a grid of electrodes, before using ultrasound to steer them around. Using this chip-like device they claim to be able to control the 10-100 micron sized bubbles, with the ultrasound matching the resonant frequency of the target bubble...