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January 13 2020

3DBuzz Closes with a Final Gift

If you wanted to learn about creating modern computer games, 3DBuzz had some of the best tutorials around. In fact, some of the tutorials about C#, C++, Android, and math would be useful for anyone, while the ones about game art and modeling in Maya are probably mostly for game developers. While these were once available only by subscription, the company — now defunct — has left them available for download at no cost.

We don’t know enough about things like Blender and Maya to evaluate the material, but it is well regarded and the ones we do know something about seem very high quality. There are, for example, many videos about C++ and C# that are very professional and cover quite a few topics.

Topics include: AI programming, ASP.net, Blender, iPhone and Android apps, C#, C++, Objective C, Python, OpenGL, HTML and JavaScript, Solidworks, Photoshop, GIMP, Unity, and several game engines like Unreal 4 and Doom 3. There are also quite a few classes on 2D and 3D art as well as related math like trig and vectors.

We don’t know how long the page will remain up, and it has an SSL issue, but to save you some time, here’s a quick way to grab all the ZIP files on a page:

wget -nc -r -np --span-host -l 1 -A zip --no-check-certificate https://3dbuzz.com/index.html

However, as you might expect, the site is overloaded, so expect to not get them all in one swoop. We were surprised they didn’t make them available as torrents. (Update: the site now says downloads are temporarily disabled, but a Reddit user did start a torrent that is missing two small files and a corrected torrent with all the files, but it may not have as many seeds.)

If you want to build games with less fuss, try this tool. Or, maybe you’d rather go old school.

Reposted byskizzo skizzo

Why Do Resistors Have a Color Code?

One of the first things you learn in electronics is how to identify a resistor’s value. Through-hole resistors have color codes, and that’s generally where beginners begin. But why are they marked like this? Like red stop signs and yellow lines down the middle of the road, it just seems like it has always been that way when, in fact, it hasn’t.

Before the 1920s, components were marked any old way the manufacturer felt like marking them. Then in 1924, 50 radio manufacturers in Chicago formed a trade group. The idea was to share patents among the members. Almost immediately the name changed from “Associated Radio Manufacturers” to the “Radio Manufacturer’s Association” or RMA.  There would be several more name changes over the years until finally, it became the EIA or the Electronic Industries Alliance. The EIA doesn’t actually exist anymore. It exploded into several specific divisions, but that’s another story.

This is the tale of how color bands made their way onto every through-hole resistor from every manufacturer in the world.

Dots Then Bands

Ésistances anciennes annees 50 by François Collard, CC-BY-SA 4.0

By the late 1920s, the RMA was setting standards and one of them was the RMA standard for color-coding. The problem was that marking small components is difficult, especially back in the 1920s.

The solution was color bands, but not quite as we know them today. The standard for colors was the same, but the body of the resistor acted as the first band. Then there would be two or three other bands to show the rest of the value. In some cases, the third band was actually a dot. So the bulk of the resistor would be the first band color. The “tip” of the resistor would be the 2nd band and a dot would be the multiplier. Radios using this scheme started to appear in 1930. Here’s the color code chart from the 1941 Radio Today yearbook:

Ads in that magazine promoting resistors were careful to note that they were RMA color-coded. The code soon extended to capacitors (condensers, in the contemporary parlance).

The dot, as with printed piece of text on the cylindrical, might be hidden from view depending on the position of the resistor. So eventually, everyone switched to bands.

The colors are meant to follow the visible spectrum (remember ROY G BIV?). However, the RMA omitted indigo because apparently many people don’t distinguish blue, indigo, and violet as three different colors; indigo is really a tertiary color, anyway and Newton included it because of his interest in the occult, apparently. That leaves four slots, so dark colors represent the low end (black and brown) and bright colors the high end (gray and white).

Of course, none of this was funny if you were color blind. Reading a resistor with a meter or a bridge out of the circuit was certainly an answer. Reading one in a circuit, though, was another matter.

The Origin of E-Series Values

In 1952 the International Electrotechnical Commission (IEC, another standards group) defined the E-series which dictates what values resistors come in so that you get equal spacing on a log scale for resistors. If that sounds confusing, consider an example.

The E12 series is for 10% resistors and the values on it give you 12 values per decade. The base values are

1, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3., 3.9, 4.7, 5.6, 6.8, 8.2

That’s why you can get, say a 4.7 K or 47 K resistor but not a 40K resistor.

However, consider the tolerance. A 10% 39 K resistor could be off by 3.9 K. If the error pushed the resistance up that would be 42.9K, making a 40 K resistor unnecessary. That is, a 39 K resistor might well be a 40 K resistor, anyway. A low 47K resistor, on the other hand, could be 42.3 K, which is less than a high-value 39 K unit.

As you might expect, the number of values goes up as the tolerance goes down. At 2%, for example, you’ll use E48 which has 48 values per decade (if you’d guess E96 — the standard used for 1% has 96 values, you’d be right). Using E48, the values near 40 K are 38.3 K and 40.2 K. That’s 39.06 on the high side and 39.2 on the low side.

Next Time

Next time you pick up a resistor and read the code from it, you can recall the history behind it all. The legacy of color bands carries over into the surface mount realm, not as color but as three digits representing the first two numbers and multiplier for the resistor’s value. These days many electronics like wireless modules and lithium batteries include a datamatrix (something like a QR code) on them. Honestly, I’m surprised that all components — through hole and surface mount — don’t have some form of micro data matrix on it that lets you point your phone at them and see their complete datasheet. Maybe one day.

Model S Motor and Volt Battery Go Together Like Peanut Butter and Jelly

A common project category on this site is “put a Raspberry Pi in it”. For people who wrench on their cars, a similarly popular project is the “LS Swap”. Over the past few years, the world of electronics and automotive hacking started to converge in the form of electric car conversions, and [Jalopnik] proclaims the electric counterpart to “LS Swap” is to put a Telsa Model S motor and a Chevy Volt battery into a project car.

The General Motors LS engine lineup is popular with petro heads for basically the same reasons Raspberry Pi are popular with the digital minded. They are both compact, very powerful for the money, have a large body of existing projects to learn from, and an equally large ecosystem of accessories to help turn ideas into reality. So if someone desired more power than is practical from a car’s original engine, the obvious next step is to swap it out for a LS.

Things may not be quite as obvious in the electric world, but that’s changing. Tesla Model S and Chevrolet Volt have been produced in volume long enough for components to show up at salvage yards. And while not up to the levels of LS swaps or Pi mods, there’s a decent sized body of knowledge for powerful garage-built electric cars thanks to pioneers like [Jim Belosic] and a budding industry catering to those who want to build their own. While the decision to use Tesla’s powerful motor is fairly obvious, the choice of Volt battery may be surprising. It’s a matter of using the right tool for the job: most of these projects are not concerned about long range offered by Tesla’s battery. A Volt battery pack costs less while still deliver enough peak power, and as it was originally developed to fit into an existing chassis, its smaller size also benefits garage tinkerers fitting it into project cars.

While Pi SBCs and LS engines are likely to dominate their respective fields for the foreseeable future, the quickly growing and evolving world of electric vehicles means this winning combo of today are likely to be replaced by some other combination in the future. But even though the parts may change, the spirit of hacking will not.

[Photo: by Jim Belosic of motor used in his Teslonda project]

Additive, Multi-Voice Synth Preserves Sounds, Too

For his final project in [Bruce Land]’s infamous microcontroller design class, [Mark] set out to make a decently-sized synth that sounds good. We think you’ll agree that he succeeded in spades. Don’t let those tiny buttons fool you, because it doesn’t sound like a toy.

Why does it sound so good? One of the reasons is that the instrument samples are made using additive synthesis, which essentially stacks harmonic overtones on top the fundamental frequency of each note. This allows synthesizers to better mimic the timbre of natural, acoustic sounds. For each note [Mark] plays, you’re hearing a blend of four frequencies constructed from lookup tables. These frequencies are shaped by an envelope function that improves the sound even further.

Between the sound and the features, this is quite an impressive synth. It can play polyphonically in piano, organ, or plucked string mode through a range of octaves. A PIC32 runs the synthesizer itself, and a pair of helper PIC32s can be used to record songs to be played over. So [Mark] could record point and counterpoint separately and play them back together, or use the helper PICs to fine-tune his three-part harmony. We’ve got this thing plugged in and waiting for you after the break.

If PICs aren’t what you normally choose, here’s an FPGA synth.

A DNA-Based Computer Calculates Square Roots Up To 900

While DNA-based computing may not be taking over silicon quite so soon, there is progress in the works. In a paper published by Small, researchers from the University of Rochester demonstrate a molecular computing system capable of calculating square roots of integers up to 900. The computer is built from synthetic biochemical logic gates using hybridization, a process where two strands of DNA join to form double-stranded DNA, and strand displacement reactions.

DNA-based circuits have already been shown to implement complex logic functions, but most existing circuits prior to the recent paper were unable to calculate square root operations. This required 4-bit binary numbers – the new prototype implements a 10-bit square root logic circuit, operating up to the decimal integer 900.

The computer uses 32 strands of DNA for storing and processing information. The process uses three modules, starting off with encoding a number on the DNA. Each combination is attached to a florescent marker, which changes signal during hybridization in the second module. The process for calculating the square root controls the signals, with the results deducted from the final color according to a threshold set in the third module.

We’re beginning to see the end of Moore’s Law approaching, with companies like Intel and AMD struggling to shrink transistors 10 nm wide. Nevertheless, with DNA molecules still about 10 time smaller than the best transistors today and DNA computing systems continuing to gain in sophistication, biochemical circuits could potentially be holding solutions to increasing the speed of computing beyond silicon computing.

Take Security Up a Notch By Adding LEDs

All computers are vulnerable to attacks by viruses or black hats, but there are lots of steps that can be taken to reduce risk. At the extreme end of the spectrum is having an “air-gapped” computer that doesn’t connect to a network at all, but this isn’t a guarantee that it won’t get attacked. Even transferring files to the computer with a USB drive can be risky under certain circumstances, but thanks to some LED lights that [Robert Fisk] has on his drive, this attack vector can at least be monitored.

Using a USB drive with a single LED that illuminates during a read OR write operation is fairly common, but since it’s possible to transfer malware unknowingly via USB drives, one that has a separate LED specifically for writing operations will help alert a user to any write operations that might be trying to fly under the radar. A recent article by [Bruce Schneier] pointed out this flaw in USB drives, and [Robert] was up to the challenge. His build returns more control to the user by showing them when their drive is accessed and in what way, which can also be used to discover unique quirks of one’s chosen operating system.

[Robert] is pretty familiar with USB drives and their ups and downs as well. A few years ago he built a USB firewall that was able to decrease the likelihood of BadUSB-type attacks. Be careful going down the rabbit hole of device security, though, or you will start seeing potential attacks hidden almost everywhere.

Hackaday Links: January 12, 2020

Nothing ruffles feathers more reliably than a software company announcing changes to its licensing terms. And so it goes with AutoDesk, who recently announced that Eagle would no longer be available as a standalone product and would now be bundled with Fusion 360. It looks like there’s still a free option for personal use, which is good even if it limits designs to two schematic sheets, two board layers, and 80 cm² board area. And perhaps this means there will be a Linux version of Fusion 360 too.

With the Y2K bug now twenty years in the rearview mirror, it’s entertaining to look back at that time and all the hype that surrounded it. Usually we talk about the effort that went into fixing vulnerable systems, but do we ever talk about the recipes of Y2K? The Advent of Computing podcast recently did an episode that gives a great background of the Y2K bug, plus discusses what people were planning to do for food after the bug detonated all the world’s nukes when the new millennium rolled around. Pantries stocked with canned goods, wood stoves to cook on and keep warm by when the powerplants all self-destructed on January 1 – it was all part of the vibe at the time.

We suppose when you put 60 birds into orbit at a time, it doesn’t take long to make a sizable impact on the planet’s constellation of satellites. Still, it came as a surprise that SpaceX was able to claim the title of world’s largest commercial satellite constellation after just three Starlink launches. We guess the operative term is “commercial” here, since some governments probably have far more satellites in service than the 182 Starlinks that have been launched so far. That’s a far cry from the 11,000 plus eventually predicted to form the Starlink constellation, but it’s already having an impact.

As a proud Idahoan, I feel personally triggered by what’s billed as the world’s first smart potato. True, I live in the part of the state with the trees and the bears, not the spuds, but still, it’s right there on our license plates. While clearly tongue-in-cheek, the Smart Potato pokes fun of our official State Vegetable, which I find beyond the pale. Seems like anything can be crowdfunded these days.

Speaking of which, check out Kohler’s Alex-connected smart toilet. For a mere $7,000 you can have a toilet that does everything a regular, boring old toilet does, but with lights. In fairness, the value of a good bidet can’t be overstated, but the ability to talk to your toilet and have it talk back seems a little on the iffy side. Perhaps teaming it up with the Charmin Poop-Bot, a self-balancing robot that connects to your phone and brings you a roll of toilet paper if you find yourself without a square to spare.

And finally, drummer Neil Peart died this week at the far-too-young age of 67. While there’s probably a fair number of Rush fans in the core hackaday demographic, there’s no hack or other tie-ins here. I’m just sad about it and wanted to share the news.

January 12 2020

DIY Ionizer Clears the Air on a Budget

Have you ever had a good, deep breath of the air near a waterfall, or perhaps after a thunderstorm? That unmistakably fresh smell is due to ionized air, specifically negative ions, and many are the claims concerning their health benefits. A minor industry has sprung up to capitalize on the interest in ionized air, and while [Amaldev] wanted to clean up the Mumbai air coming into his home, he didn’t want to pay a lot for a commercial unit. So he built his own air ionizer for only about $10.

When [Amaldev] dropped this in the Hackaday tip line, he indicated that he’d been taking some heat for the design from Instagram followers. We imagine a fair number of the complaints stem from the cluster of sewing needles that bristle from one end of the PCB and are raised to 6,000 volts by a fifteen-stage Cockcroft-Walton multiplier. That’s sure to raise eyebrows, or possible the hair on one’s head if you happen to brush by the emitters. Or perhaps [Amaldev]’s critics are dubious about the benefits of ionized air; indeed, some commenters on the video below seem to think that the smoke in the closed jar was not precipitated by the ion stream as [Amaldev] claims, but rather somehow was settled by heat or some other trickery.

Neither of those bothers us as much as the direct 230-volt mains connection, though. We’d have preferred to see at least an isolation transformer in there, or perhaps a battery-powered flyback circuit to supply the input to that multiplier. Still, the lesson on cascade multipliers was welcome, and we found the smoke-clearing power of ionized air pretty amazing.

<!--[if lt IE 9]><script>document.createElement('video');</script><![endif]--> https://hackaday.com/wp-content/uploads/2019/12/81606994_136216931163169_4519509951028015416_n.mp4

Awakening A Dragon From Its Slumber

For all the retrocomputing fun and games we encounter in our community, there are a few classic microcomputers that rarely receive any attention. Usually this is because they didn’t sell well and not many have survived, or were simply underwhelming machines that haven’t gathered a huge following today. One that arguably falls within both camps is the Dragon 32, a machine best known in those pre-Raspberry Pi days for being the only home computer manufactured in Wales, and for being nearly compatible with the Tandy Color Computer due to both machines’ designs coming from the same Motorola data sheet. Repeat restorer of retrocomputers, [Drygol], has given a Dragon 32 the full restoration and upgrade treatment, offering us a rare chance to take a look at this computer.

The Dragon arrived with a pile of contemporary books and software, but no power supply. A significant modification was made to the internal PSU board then to allow it to work with an Amiga unit, and the black-on-green Dragon text came up on the TV screen. Recapping and a replacement for a faulty op-amp fixed poor video quality, then it was time for a 64K memory upgrade with some neatly done bodge-wiring. Finally there’s a repair to the very period-looking analogue joystick, and a home-made interface for the more common Atari/Amiga style sticks.

The Dragon may be only a footnote in the history of 8-bit home computing, but with its good expandability and decent quality keyboard it perhaps deserved to reach more homes than it did. This appears to be the first time a Dragon has featured here, though its Tandy CoCo cousin has made it into a few stories.

Maze Solving Via Text Editing

Linux scripters usually know about sed — the stream editor. It has a simple job: transform text as it whizzes from input to output. So if you wanted to solve a maze, this wouldn’t be the tool you’d think to use, right? Well, if you were [xsot], you’d disagree.

You build a maze using spaces for empty space and # for walls. There’s an S to mark the start position and an E to mark the end. Of course, the maze can also contain newlines. The sed script does an amazing job of solving the problem.

As the author points out:

The main difficulty lies in the lack of the luxuries usually provided in a regular programming language such as:

  • arithmetic
  • data types other than strings
  • more than 2 “variables”

Also, sed regex lacks features present in other regex systems such as PCRE (non-greedy matching, lookaheads, etc).

We will confess, we didn’t pull the whole 122 line script apart to understand it, but it looks like it replaces spaces with special marker characters that relate to the direction from the end to the start. The characters U, D, L, and R indicate the direction. Then it is able to select the closest character and replaces them with arrows (well, a letter v, a caret, and the less than and greater than signs).

A very unusual hack of using sed, we think. The output is even colorized and animated. Amazing.

We can’t say we’ve ever done anything this bizarre with a scripting command. We have looked at scripting many times, though, if you want to brush up. Probably the closest we’ve come is using bash scripts to process binary files.

Generating Beetles from Public Domain Images

Ever since [Ian Goodfellow] and his colleagues invented the generative adversarial network (GAN) in 2014, hundreds of projects, from style transfers to poetry generators, have been produced using the concept of contesting neural networks. Unlike traditional neural networks, GANs can generate new data that fits statistically within the same set as the training set.

[Bernat Cuni], the one-man design team behind [cunicode] came up with the idea to generate beetles using this technique. Inspired by material published on Machine Learning for Artists, he decided to deploy some visual experiments with zoological illustrations. The training data was found from a public domain book hosted at archive.org, found through the Biodiversity Heritage Library. A combination of OpenCV and ImageMagick helped with individually extracting illustrations to squared images.

[Cuni] then ran a DCGAN with the data set, generating the first set of quasi-beetles after some tinkering with epochs and settings. After the failed first experiment, he went with StyleGAN, setting up a machine at PaperSpace with 1 GPU and running the training for >3 days on 128 px images. The results were much better, but fairly small and the cost of running the machine was quite expensive (>€125).

Given the success of the previous experiment, he decided to transfer over to Google CoLab, using their 12 hours of K80 GPU per run for free to generate some more beetles. With the intent on producing more HD beetles, he used Runway trained on 1024 px beetles, discovering much better results after 3000 steps. The model was moved over to Google CoLab to produce HD outputs.

He has since continued to experiment with the beetles, producing some confusing generated images and fun collectibles.

Check out the beetles here:

A Supercapacitor Might Just Light Your Way One Day

Sometimes the simplest hacks are the most useful ones, and they don’t come much simpler than the little supercapacitor LED flashlight from serial maker of cool stuff [Jeremy S. Cook]. Little more than an LED, a supercapacitor, USB plug, and couple of resistors, it makes a neat little flashlight that charges from any USB A power socket and delivers usable light for over half an hour.

It’s neat, but on its own there’s not much to detain the reader until it is revealed as a “Hello World” supercapacitor project from an article in which he delves into the possibilities of these still rather exotic components. Its point is to explore their different properties when compared to a battery, for example a linear voltage drop in contrast to the sharp drop-off of a chemical cell. In the video below the break we see him try a little boost regulator to deliver a constant voltage, with consequent severe loss of lighting time for the LED. It’s by this type of experimentation that we learn our way around a component unfamiliar to us, and the article and video are certainly worth a look if you’ve never used a supercapacitor before.

NanoVNA Tests Antenna Pattern

When [Jephthai] wanted to build his own Yagi antenna, he turned to MMANA software for antenna modeling. This is an antenna analysis program that uses the moment method to calculate parameters for different antenna geometries. After building the Yagi, the predicted tuning and impedance matched the real antenna nicely. But what about the radiation pattern? To test that, he used a NanoVNA and a clever test setup.

He needed a test spot out of the antenna’s near field so he set up his workstation 18 feet away from the test antenna which was on a mount that could rotate. On the edge of the workstation table — affixed with painter’s tape — is a NanoVNA connected to a laptop.

The rest is just sweat work. First, make a measurement on the resonant frequency. Then rotate the antenna 10 degrees and repeat. After 36 measurements you have the entire circle.

Plotting the resulting data with GNUPlot matched up pretty well with the antenna’s predicted performance. This was actually the second attempt and in the report, [Jephthai] reports that keeping alignment is critical to get everything to work. You can see in his pictures some of the steps he took to maintain consistency.

Another aid to consistency was the use of the NanoVNASaver software. This software allows for a frequency sweep along with a display and the creation of Touchstone files.

We’ve looked at the NanoVNA before. If you’d rather view your antenna pattern as a 3D volume, break out the 3D printer.

This Artist Drags His Feet Across Sand and Snow

You may have seen Simon Beck’s work a few years back. The snow artist, known for creating large-scale works of art with nothing but snowshoes, has been creating geometrically inspired fractals and mathematical forms for years. An orienteer and map-maker by day, he typically plans out his works in advance and chooses sites based on their flat terrain. The lack of slopes prevents skiers from traversing the area beforehand and helps with measuring the lines needed to create the drawing.

He starts off by measuring the distance he has to be from the center by using a compass and walking in a straight line towards a point in the distance, making curves based on relative position to other lines. Once the primary lines are made, he measures points along the way using pace counting and joins secondary lines by connecting the points. The lines are generally walked three times to solidify them before filling in the shaded areas. The results are mesmerizing.

He has since expanded to sand art, using the same techniques that gained him fame in ski resorts and national parks on the sandy shores. Unfortunately, tidal patterns, seaweed, and beach debris make it slightly harder to achieve pristine conditions, but he has managed to create some impressive works of art nonetheless.

 

Plucky Kalimba Plays Itself

[Gurpreet] fell in love with the peaceful, floaty theme from the Avatar series and bought a kalimba so he could hear it resonate through his fingertips. He soon realized that although it’s nice to play the kalimba, it would be a lot cooler if it played itself. Then he could relax and enjoy the music without wearing out his thumbs.

After doing a bit of experimentation with printing tine-plucking extensions for the servo horns, [Gurpreet] decided to start the design process by mounting the servos on a printed base. The servos are slotted into place by their mounting tabs and secured with hot glue. We think this was a good choice — it’s functional and it looks cool, like a heat sink.

[Gurpreet]’s future plans include more servos to pluck the rest of the tines, and figuring out how feed it MIDI and play it real time. For the demo after the break, [Gurpreet] says he lapel mic’d the kalimba from the back and cut out the servo noise with Audacity, but ultimately wants to figure out how to quiet them directly. He’s going to try lubing the gears and making a sound-dampening enclosure with foam, but if you have any other ideas, let him know down below.

We don’t see too many kalimba projects around here, but here’s one connected to a Teensy-based looper.

Via [r/arduino]

January 11 2020

Printed Separator Separates Printed Pages

We all know people trapped in aging bodies who can’t do all the things they used to do. It’s easy to accept that you may never move small furniture around by yourself again, but losing the ability to do something as simple as separating the pages of your newspaper to keep reading it is an end to enjoyment.

When [Randomcitizen4] visited his grandma over the holidays, she mentioned having trouble with this, among other things. He fired up his printer and got to work designing a device to help her get back to the funny pages. This simple gripper mechanism uses rubber bands for tension and flexible filament to get a firm grip on the paper. The jaws default to the open position so they’re ready to grab some newsprint, and a light squeeze of the handles slides the top page back from the stack, creating a gap for Grandma’s fingers. You can see a demo on page 32 after the break.

Although the device does work on some books and magazines, he’d like to improve the design of the grips to make the device more universally useful. [Randomcitizen4] says he tried a few things already, but we wonder if a more complex surface pattern might do the trick — maybe less like fins and more like a tire tread pattern. All the STLs are available if you want to give it a go.

If Grandma’s newspaper ever goes out of print, she should still be able to read it on a tablet or an e-reader. Then maybe [Randomcitizen4] can build some kind of remote-controlled page turner for her.

An Arduino-Based Flute Playing Machine

It’s one thing to be able to transcribe music from a flute, and it’s another to be able to make a flute play pre-written music. The latter is what [Abhilash Patel] decided to pursue in the flute player machine, an Arduino-based project that uses an air flow mechanism and PVC pipes to control the notes produced by a makeshift flute. It’s currently able to play 17 notes, just over two octaves starting from the lowest frequency of E.

In order to play songs, the tones have to either be directly coded and uploaded to the Arduino, composed with a random note generator, or detected from a microphone. While a real flute can be used for the machine, [Patel] uses a PVC flute, constructed with some knowledge of flute playing.

The resonant frequency is based on the effective length, hole sizes, and pipe diameter, so it is fairly difficult to correctly tune a homemade flute. Nevertheless, calculating the length as c/2f where c is the speed of sound (~345 m/s) and f is the frequency of the note can help with identifying the location of the holes. [Patel] cut the PVC pipe and sealed off one end, drilling a blowing hole at 1.5 x the pipe diameter. After playing the flute, the end of the pipe was filled until the frequency exactly matched the desired note.

The hole covering uses cuttings of pipe attached to a cable connecting to a servo. The motors are isolated inside a box to keep the wires clear and area all able to be powered with 5 V. As for the software, the code is primarily used to control when the fan is blowing and which holes are covered to produce a note.

Listen to the flute play “My Heart Will Go On” from Titanic in the video below. Now the next step might just be making the flute playing machine automatically play sheet music – imagine the possibilities!

Stacks of Spring Washers Power the Drawbar on this CNC Mill Conversion

With Tormach and Haas capturing a lot of the entry-level professional market for CNC machines, we don’t see too many CNC conversions of manual mills anymore. And so this power drawbar conversion for a Precision Matthews mill really caught our eye.

What’s that, you say? Didn’t [Physics Anonymous] already build a power drawbar for a mill? They did, and it was quite successful. But that was based on a pneumatic impact wrench, and while it worked fine on a manual mill, the same approach would be a bit slow and cumbersome on a CNC mill. For this build, they chose a completely different approach to providing the necessary upward force to draw the collet into the collet holder and clamp down on the tool: springs. Specifically, Belleville spring washers, which are shaped like shallow cups and can exert tremendous axial force over a very short distance.

[PA] calculated that they’d need to exert 2,700 pounds (12,000 Newtons) of force over a length of a couple of inches, which seems outside the Belleville washer’s specs. Luckily, the springs can be stacked, either nested together in “series” to increase the load force, or alternating in “parallel” to apply the rated force over a greater distance. To compress their stack, they used a nifty multi-stage pneumatic cylinder to squash down the springs and release the collet. They also had to come up with a mechanism to engage to machine’s spindle only when a tool change is called for. The video below details the design and shows the build; skip to 11:32 to see the drawbar in action.

We’re looking forward to the rest of [Physics Anonymous]’ conversion. They’re no strangers to modifying off-the-shelf machines to do their bidding, after all – witness their improvements to an SLA printer.

Building a Real Wooden Table Saw

A table saw is one of those tools that aren’t strictly necessary to have, but immensely helpful if you do happen to have one around. The folks at [I Build It] have made a three part series that features a homemade table saw build, so you can finally get around to adding one to your makerspace.

The build uses a real table saw arbor and is made from Baltic birch plywood and solid wood, with some plastic sheets for the trunnions and top. The blade is housed in a blade lift made out wooden panels with a pivot point and slot for the lift mechanism. Bearings allow the blade the freedom of movement, while a curved cutout allows it to stay flat against the wall of the slot while the blade lift mechanism moves.

Meanwhile a reused motor from a previous table saw is dusted, cleaned, and rewired to run in reverse. While most table saws only need two trunnions, a third is used for supporting the motor, since it has to move with the lift and tilt. Once the lift/tilt mechanism is complete, the frame for the table saw is more straightforward, with many steps involving clamping, measuring, cutting, fitting, and painting the assembly. For the final few steps, a switched is mounted outside the table saw in a small box that connected to the power supply and motor, as well as a shop vac for handling dust collection from the saw. While the enclosure isn’t a metal box, as long as the connections are secured properly the wires shouldn’t come loose.

If you want to see other examples of homemade table saws, check out this teeny tiny saw and this kid-friendly table saw build.

This Ugly Christmas Sweater Can Set You On Fire

While Christmas may have just passed, there’s just enough time left in winter to justify wearing your ugly Christmas sweaters for a few more days. If you’re not one of the lucky ones with an old sweater from Grandma, you can still turn your least favorite sweater into the most epic flame-throwing Christmas sweater there ever was.

[JAIRUS OF ALL], maker of explosive and other dangerous ideas, came up with a DIY ugly Christmas sweater that shoots flames on command. In order to produce the flame-throwing effect, he uses piping from a fish tank airline hose with a T connector attached to one end and epoxied to the middle of the sweater. The piping runs down the sweater to a can of butane fuel that he can control from the nozzle. Once the fuel is being released, he uses a lighter to initiate the flames from the sweater.

The flames are quite impressive, so definitely use caution if you intend to replicate this build in any way. It would be helpful to have a friend with a CO2 fire extinguisher nearby as well.

For a less life-threatening build, fellow builder [Price] created a Christmas tree-themed sweater lined with LEDs and USB-powered figurines, connected to a power supply in his pocket.

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