A 3.3 V Tube Preamp Without An Inverter

February 8, 2020 by Jenny List 34 Comments

If you’ve ever worked with vacuum tubes, you’ll probably have a healthy appreciation for high voltage power supplies. These components require higher potentials to get those electrons moving, or so we’re told. It’s not the whole truth though, as [Albert van Dalen] demonstrates with his tube preamplifier running from only 3.3 V. If your first thought is that he must have made a flyback converter to step that voltage up to something more useful then you’re in for a surprise, because the single 6J6 pentode really does run from just 3.3 volts. Even its heater, normally supplied with 6.3 V, takes the lower voltage.

The circuit appears at first sight to be a conventional single-ended design, but closer examination reveals a grid bias circuit more reminiscent of a bipolar transistor. This results in a positive grid voltage rather than the more usual negative, and an unusually high 0.3 mA grid current. The cathode current is only 0.15 mA, but the preamplifier delivers a 3.5x gain. There is more detail on his website.

It would be interesting to subject this circuit to a full audio analysis and comparison with a more conventional design. As with so much in the world of audio there’s some smoke and mirrors around what constitutes the so-called “valve sound”, and it’s a question whether the satisfaction comes through the sound itself or the bragging rights of having a unit with a vacuum tube on show. Still, this is a simple enough design which takes few resources to build, so we look forward to seeing further experimentation. Careful though – down the vacuum audio route can lie folly.

This PIC Is A Squarewave Generator

February 8, 2020 by Jenny List 18 Comments

When we use a microcontroller to flip a few GPIOs or talk SPI to a peripheral chip, we are often overlooking that it will usually contain an array of built-in peripherals that were once the preserve of extra hardware. Analogue ports, timers, UARTs, and clock generators, to name just a few. [Giovanni Bernardo] has been experimenting with one of these, the internal frequency synthesiser on many PIC microcontrollers, and he’s produced a handy square wave generator for which he’s placed code on GitHub and produced a write-up (Italian language, Google translate link).

The board used is a PIC16F375 Curiosity Nano, and code takes input from a rotary encoder to set the frequency, with a button to select different step sizes and an alphanumeric LCD display to show the current settings. Frequencies from 1 Hz to 15 MHz are possible, with a clever switch between two of the PICs internal clocks to be used as the reference frequency. Stability depends upon whatever source the PIC uses for its own clock, and while we suspect that will be enough for most users it’s not inconceivable that the PIC could be clocked from a GPS-disciplined source or similar were there a requirement for it.

There are plenty of ways to generate square waves from a microcontroller. Most projects use waveform generator ICs.

A Very Buttoned Up Raspberry Pi Media Server

February 7, 2020 by Tom Nardi 21 Comments

Projects that turn the Raspberry Pi into a low-cost Network Attached Storage (NAS) solution are very common; all you need is the right software, the Pi itself, and some USB storage devices. But unless you particularly like the “Medusa” look, with loose cables running all over the place, you’ll probably want to put the hardware into a suitable enclosure. Unfortunately, that’s where the somewhat unusual layout of the Pi can make things tricky.

Which is why [AraymBox] came up with this unique “capsule” enclosure for the Raspberry Pi and two USB-attached hard drives. Every effort has been made to keep the outside of this design as clean and streamlined as possible. The asymmetrical loops of wires that we so often see on other projects are gone, with everything been brought inside thanks to some clever wiring. This enclosure looks like a professional product, and if you’re willing to put in the effort, you can have one to call your own.

The good news is that the 3D printed enclosure only has four parts, albeit rather large ones, and none of which require support material. So it should be an easy print even on a relatively low-end machine. Of course, you’re not going to get that futuristic metallic look without a little work. You’ll need to do a considerable amount of sanding, filling, and paint work to get that kind of a surface finish. Then again, that rough “just printed” look has a certain cyberpunk appeal to it as well.

But the printed enclosure is only half the battle. Inside, [AraymBox] has soldered the USB to SATA adapter cables directly to the Raspberry Pi to keep things tight and compact. A micro USB breakout board was then used to add a power connector on the back of the device where the Ethernet and USB ports are, solving the issue of having one lonely USB cable coming out of the side of the case.

In the past we’ve seen other attempts to create a 3D printable enclosure for Pi servers, with varying levels of success. While some would argue that the better solution is to just throw the Pi and the drives in a large enough enclosure that it doesn’t matter what the wiring looks like, we appreciate the effort that some hackers are willing to put in to make something custom.

Hacking Multiplication: Binary Multiply On Paper

February 7, 2020 by Al Williams 12 Comments

We’ve often noted that whether had ancient man known binary, we could all count to 1023 on our fingers. We thought about that while watching [Numberphile’s] latest video about “Russian” multiplication (see below). Apparently, the method dates back quite a way, sometimes known as Ethiopian or peasant multiplication. Even the ancient Egyptians did a form of it.

If you’ve ever written long multiplication code for a microcontroller, you can probably tell how this works. Each halving of the number amounts to a right shift. Each doubling is a left shift. Throwing out the even numbers means you only take the values when the least-significant bit is zero. Booth’s algorithm is more efficient, but the “Russian” method is simple to do on paper.

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Stylish Outfit Packs A Solar Charging Rig

February 7, 2020 by Lewin Day 6 Comments

Being out and about with your devices rapidly running out of battery power can rapidly turn into a sticky situation. Suddenly you find yourself unable to hail rideshares and incapable of transferring money around. For the fashion conscious who wish to avoid this, [Kitty Yeung]’s design may be a valuable addition to their summer closet.

The project starts with [Kitty] sewing an elegant bodice and shorts out of a silky silver material. This fabric tends to fray when cut, so fabric glue and iron-on tape was used to protect the edges. This also makes sure the garment doesn’t fall to pieces when washed or worn often. Ribbons, pockets, and other features were designed into the garments to integrate them with hardware to enable the garments to act as a portable charging solution. 3D-printed brackets are affixed to the shoulders, holding a solar panel in an upward-facing angle to catch a good amount of sun. The panel chosen integrates circuitry to output a nice, clean 5V output for charging devices over USB.

It’s a fashionable outfit that also packs useful hardware, and we agree with [Kitty] that it really would be perfect for Burning Man. The cone hat was a nice touch, too. It’s not the first time we’ve heard from [Kitty] either – she appeared as a speaker at 2018’s Hackaday Superconference, too!

A Laser Drawing Machine For Flashes Of Creativity

February 7, 2020 by Kristina Panos 6 Comments

Ahh, midterms. Some students blow off steam between study sessions by playing video games or just zoning out. While those kids were all distracted, [Justinwong777] and his buddy [Brett] found a bunch of scrap wood and built this laser drawing machine in their school’s makerspace. You operate it as you might an Etch-a-Sketch, except your drawings are as fleeting as sparkler art on the 4th of July, if they made Tron-colored sparklers.

Though you work it like an Etch-a-Sketch, the business end operates like a laser cutter. Inside that plywood enclosure is an Arduino Uno and a pair of motors. These motors turn a series of custom gears, which move a small mirror angled at 45° in the xy-plane. There’s a 30mW laser mounted parallel with the base, pointed at the mirror, and it reflects the beam toward a canvas panel coated with phosphorescent paint. We dig the printed ergonomic case for the joystick, which gives control of both x and y. Put on some eye protection and check it out after the break.

If you want to draw with lasers, but aren’t much of an artist, do something unexpected: build a laser turret not to kill, but to draw the weather on the wall.

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Mitch Altman Asks How You’re Using Your Life

February 7, 2020 by Mike Szczys 57 Comments

This talk will probably make you a bit angry. You might be upset with some of Mitch Altman’s views or his hyperbole in describing them. Or you might be upset because you totally agree with his views and feel the same disappointment he does with many (ab)uses of technology. Either way, the point of his talk, which was given at the 2019 Hackaday Superconference, is that we all should think deeply about what we choose to do with our time and our talents. Consider yourself challenged.

The video below is packed full of colorful ideas, along with some colorful language. Let’s take a look.

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