Want Octoprint But Lack A Raspberry Pi? Use An Old Android Phone

November 27, 2021 by 21 Comments

3D printers and Octoprint have a long history together, and pre-built images for the Raspberry Pi make getting up and running pretty easy. But there’s also another easy way to get in on the Octoprint action, and that’s to run it on an Android phone with the octo4a project.

A modern smartphone has a lot of useful features that make it attractive as an Octoprint host. There is a built-in touchscreen, easy power management, a built-in camera, and the fact that people regularly upgrade to new phones means that older Android phones — still powerful pieces of hardware in their own right — are readily available at low cost. The project is still relatively new, so don’t forget to check the Octoprint community thread for this project if you give it a try.

If you are wondering what Octoprint is and what it brings to the table, our own Tom Nardi explained what it does and why it matters when he shared his own upgrade experience from 2018. A few details are no longer current — for example one is no longer likely to encounter a Printrbot — but it’s still a perfectly valid primer on adding great management functionality to a 3D printer.

Ham Radio Gets Brain Transplant

November 27, 2021 by 7 Comments

Old radios didn’t have much in the way of smarts. But as digital synthesis became more common, radios often had as much digital electronics in them as RF circuits. The problem is that digital electronics get better and better every year, so what looked like high-tech one year is quaint the next. [IMSAI Guy] had an Icom IC-245 and decided to replace the digital electronics inside with — among other things — an Arduino.

He spends a good bit of the first part of the video that you can see below explaining what the design needs to do. An Arduino Nano fits and he uses a few additional parts to get shift registers, a 0-1V digital to analog converter, and an interface to an OLED display.

Unless you have this exact radio, you probably won’t be able to directly apply this project. Still, it is great to look over someone’s shoulder while they design something like this, especially when they explain their reasoning as they go.

The PCB, of course, has to be exactly the same size as the board it replaces, including mounting holes and interface connectors. It looks like he got it right the first time which isn’t always easy. Does it work? We don’t know by the end of the first video. You’ll have to watch the next one (also below) where he actually populates the PCB and tests everything out.

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Perovskites Understood

November 27, 2021 by 9 Comments

The usual solar cell is made of silicon. The better cells use the crystalline form of the element, but there are other methods to obtain electric energy from the sun using silicon. Forming silicon crystals, though, can be expensive so there is always interest in different solar technologies. Perovskite is one of the leading candidates for supplanting silicon. Since they use lead salts, they are cheap and simple to construct. The efficiency is good, too, even when the material is not particularly well ordered. The problem is every model science has on what should make a good solar cell predicted that orderly compounds would perform better, even though this is not true for perovskite. Now scientists at Cambridge think they know why these cells perform even in the face of structural defects.

Perovskites take their name from a natural mineral that has the same atomic structure. In 2009, methylammonium lead halide perovskites were found to act as solar cells. Conversion rates can be as high as 25.5% according to sources and — apparently — the cells could be as much as 31% efficient, in theory. Solar cells top out — again, in theory — at 32.3% although in the real world you are lucky to get into the high twenties.

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Indoor Blimp Sails Through The Air Using Ultrasonic Transducers

November 27, 2021 by 25 Comments

Quadcopter type drones can be flown indoors, but unless you have a lot of space, it usually just ends in a crash. The prospect of being hit in the face by the propellor blades, spinning at 10k RPM doesn’t bear thinking about, and then there’s the noise. So, as a solution for indoor photography, or operating in public spaces, they are not viable. Japanese mobile operator DOCOMO has a new take on an old idea; the blimp. But, surely even a helium filled vehicle needs blades to steer around the room, we hear you cry? Not so, if you use a pair of specialised ultrasonic transducer arrays to move the air instead! (Video, embedded below)

Three banks of thrusters provide a 180 degree steerable net force

Details are scarce, but DOCOMO have fitted a helium balloon with modules on either side that can produce a steerable thrust, allowing the vehicle to effect all the expected aerial manoeuvres with ease and grace. The module at the bottom contains the control electronics, an upwards facing RGB LED for some extra bling, and of course a video camera to capture those all-important video shots.

We’d love to find a source for those ultrasonic transducer devices, and can only guess at the physical arrangement that allows for air to pass in one direction only, to effect a net thrust. We can find a few research papers hinting at the ability to use ultrasound to propel through air, like this one (bah! IEEExplore Paywall!) but to our knowledge,  this technology is not quite in the hands of hackers just yet.

Blimps are by no means scarce on these fine pages, here is a Blimpduino, an Arduino controlled 3D printed blimp, an illuminated blimp art installation by Japanese artist [Kensho Miyoshi] and if using helium is just too darn safe for you (or if you want to help prevent this allegedly precious resource from being lost into space) you could just build a remote controlled blimp using hydrogen instead. Just don’t light a match.

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PiGlass V2 Embraces The New Raspberry Pi Zero 2

November 27, 2021 by 4 Comments

Well, that certainly didn’t take long. It’s been just about a month since the Raspberry Pi Zero 2 hit the market, and we’re already seeing folks revisit old projects to reap the benefits of the drop-in upgrade that provides five times the computational power in the same form factor.

Take for example the PiGlass v2 that [Matt] has been working on. He originally put the Pi Zero wearable together back in 2018, and while it featured plenty of bells and whistles like a VuFine+ display, 5 MP camera, and bone conduction audio, the rather anemic hardware of the original Zero kept it from reaching its true potential.

But thanks to the newly released Pi Zero 2, slapping quad-core power onto the existing rig was as easy as unplugging a couple cables and swapping out the board. With the increased performance of the new Pi, he’s able to play multimedia content through Kodi, emulate classic games with RetroPie, and even stream live video to YouTube. Using the custom menu seen in the video below, a small off-the-shelf Bluetooth controller from 8BitDo is all he needs to control the wearable’s various functions without getting bogged down with a full keyboard and mouse.

Although it might not have the punch of its larger siblings, the new Pi Zero 2 is definitely a very exciting platform. The highly efficient board delivers performance on par with the old Pi 3, while still being well positioned for battery powered projects like this one. We’re eager to see what develops as the new SBC finds its way into the hands of more hackers and makers in the coming months.

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LEDs display different pitches in a sunburst pattern

Spiral Music Visualization

November 26, 2021 by 6 Comments

Displaying notes live as they are being played can be a really powerful learning tool, but it’s usually used to learn how to play a specific instrument. This take on the topic is actually a neat way to learn more about music theory — how pitches work together to build the sounds that we hear. The visual tack chosen arranges each of 12 notes into a spiral. As you continue to go up the scale through more octaves, pitches that share the same name line up into a line like a ray projecting out from the sun. So there are 12 rays for the notes in the scale: C, C#/D♭, D, D#/E♭,F, etc.

[mechatronicsguy] built it a few years back but just now got around to documenting it, and we’re sure glad he did. The layout of notes at first looks just like a colorful visualization. But as he mentions in his description, this assigns a shape to each different type of cord. A major cord will have the same shape whether it is played with C, G#, B♭, or any other note as the root. The shape simply rotates around the axis based on that root note. Higher octaves will be shown further out on the radius, but the chord shape will still be the same. Minor, augmented, even modal chords and those with added pitches all have their own unique shape on the display.

You get the best understanding of the visualization by looking at the Python-rendered version in the video below. It’s a nice touch that notes turn grey and fade away after being released so you kind of see where the current chord came from. This isn’t strictly a perk of pre-recordings. While you can feed it MIDI files, you can also play a MIDI instrument and display the visuals live on the hardware version that uses a Teensy with an audio shield.

If you’re looking for examples on how music visualizers are used to teach the instrument, look no further than this Wurlitzer note visualizer replica. Also for those who don’t know, the song being played in the hardware demo (second video below) is Beethoven’s 7th Symphony. Well worth a full listen, it’ll change your life.

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Finally, Tame The Si5351!

November 26, 2021 by 12 Comments

The Si5351 is an extremely useful device, containing multiple clock generators with many versatile programming options that go well beyond its original purpose of providing a clock for digital circuitry. It has in particular found a spot in RF projects, where it provides a cheap and effective stand-in for a variable frequency oscillator in everything from receivers to VNAs. It’s fair to say that programming the Si5351 isn’t the easiest of tasks though, and joining the various attempts to make this simpler is [MR-DOS], who has created an Si5351 library for the STM32 range of ARM Cortex M processors. Fortunately for those afflicted by the semiconductor shortage there’s the advice that porting it to other architectures should only require the relatively manageable task of modifying the i2c function for the new hardware.

Instead of being a full abstraction layer for frequency generation, this library provides functions to give access to the nuts-and-bolts of the chip such as PLL dividers. Thus there’s a need to understand the workings of a PLL and calculate its parameters, while in return much more flexibility over the chip’s operation can be had. We like this approach even though it requires a little more work from the developer.

Over the years this device has attracted a variety of libraries, this isn’t the first we’ve featured.

Header image: Adafruit Industries (CC BY-NC-SA 2.0)