Bessel Filter Design

Once you fall deep enough into the rabbit hole of any project, specific information starts getting harder and harder to find. At some point, trusting experts becomes necessary, even if that information is hard to find, obtuse, or incomplete. [turingbirds] was having this problem with Bessel filters, namely that all of the information about them was scattered around the web and in textbooks. For anyone else who is having trouble with these particular filters, or simply wants to learn more about them, [turingbirds] has put together a guide with all of the information he has about them.

For those who don’t design audio circuits full-time, a Bessel filter is a linear, passive bandpass filter that preserves waveshapes of signals that are within the range of the filter’s pass bands, rather than distorting them in some way. [turingbirds]’s guide goes into the foundations of where the filter coefficients come from, instead of blindly using lookup tables like he had been doing.

For anyone else who uses these filters often, this design guide looks to be a helpful tool. Of course, if you’re new to the world of electronic filters there’s no reason to be afraid of them. You can even get started with everyone’s favorite: an Arduino.

Harrier-like Tilt Thrust in Multirotor Aircraft

A traditional quadcopter is designed to achieve 6 degrees of freedom — three translational and three rotational — and piloting these manually can prove to be a challenge for beginners. Hexacopters offer better stability and flight speed at a higher price but the flight controller gets a bit more complex.

Taking this to a whole new level, the teams at the Swiss Federal Institute of Technology (ETH Zürich) and Zurich University of the Arts (ZHDK) have come together to present a hexacopter with 6 individually tiltable axes. The 360-degree tilt in rotors allows for a whopping 12-degrees of freedom in flight and allows the UAV to fly in essentially any direction including parallel to walls.

In addition to the acrobatic capabilities of the design, the team has done some testing with autonomous control using external cameras. Their blog contains videos of their testing at various stages and it interesting to see the project evolve over a short span of nine months. Check out the video below of the prototype in action.

With Amazon delivering packages via drone and getting patents for parachute labels, UAV design is evolving faster now than ever. We can’t wait to see where this 12 DOF takes the state of the art. Continue reading “Harrier-like Tilt Thrust in Multirotor Aircraft”

On Point: The Yagi Antenna

If you happened to look up during a drive down a suburban street in the US anytime during the 60s or 70s, you’ll no doubt have noticed a forest of TV antennas. When over-the-air TV was the only option, people went to great lengths to haul in signals, with antennas of sometimes massive proportions flying over rooftops.

Outdoor antennas all but disappeared over the last third of the 20th century as cable providers became dominant, cast to the curb as unsightly relics of a sad and bygone era of limited choices and poor reception. But now cheapskates cable-cutters like yours truly are starting to regrow that once-thick forest, this time lofting antennas to receive digital programming over the air. Many of the new antennas make outrageous claims about performance or tout that they’re designed specifically for HDTV. It’s all marketing nonsense, of course, because then as now, almost every TV antenna is just some form of the classic Yagi design. The physics of this antenna are fascinating, as is the story of how the antenna was invented.

Continue reading “On Point: The Yagi Antenna”

AI Generates Color Palettes; Has Remarkably Good Taste

Color palettes are key to any sort of visual or graphic design. A designer has to identify a handful of key colours to make a design work, making calls on what’s eye catching or what sets the mood appropriately. One of the problems is that it relies heavily on subjective judgement, rather than any known mathematical formula. There are rules one can apply, but rules can also be artistically broken, so it’s never a simple task. To this end, [Jack Qiao] created colormind.io, a tool that uses neural nets to generate color palettes.

It’s a fun tool – there’s a selection of palettes generated from popular media and sunset photos, as well as the option to generate custom palettes yourself. Colours can be locked so you can iterate around those you like, finding others that match well. The results are impressive – the tool is able to generate palettes that seem to blend rather well. We were unable to force it to generate anything truly garish despite a few attempts!

The blog explains the software behind the curtain. After first experimenting with a type of neural net known as an LSTM, [Jack] found the results too bland. The network was afraid to be wrong, so would choose values very much “in the middle”, leading to muted palettes of browns and greys. After switching to a less accuracy-focused network known as a GAN, the results were better – [Jack] says the network now generates what it believes to be “plausible” palettes. The code has been uploaded to GitHub if you’d like to play around with it yourself.

Check out this primer on neural nets if you’d like to learn more. We’d like to know – how do you pick a palette when starting a project? Let us know in the comments.

A Tool For KiCad Board Renderings

If you’re producing documentation for a PCB project, you might as well make the board renders look good. But then, that’s a lot of work and you’re not an artist. Enter [Jan]’s new tool that takes KiCad board files, replaces each footprint with (custom) graphics, and provides a nice SVG representation, ready for labelling. If you like the output of a Fritzing layout, but have higher expectations of the PCB tool, this is just the ticket.

We all love [pighixx]’s pinout diagrams. Here’s his take on the Arduino Uno, for instance. It turns out that he does these largely by hand. That’s art for ya.

Sparkfun has taken a stab at replicating the graphical style for the pin labels, but then they toss in a photo of the real item. [Jan]’s graphic PCB generator fills in the last step toward almost putting [pighixx] out of a job. Get the code for yourself on GitHub.

Bad Thermal Design And Burning Down The House

Control boards for 3D printers are a dime a dozen on the usual online marketplaces, and you usually get what you pay for. These boards can burn down your house thanks to a few terrible design choices. [Scott Rider] aka [Crow] took a look at the popular Melzi board, and what he found was horrifying. These boards overheat right at the connector for the heated bed, but the good news is these problems are easily fixed.

The Melzi board has a few problems with its PCB design. The first and most glaring issue is the use of thermals on the pads for the heated bed connector. In low-power applications, thermals — the method of not connecting the entire top or bottom layer to a hole or pad — are a great idea. It makes it easier to solder, because heat isn’t transmitted as easily to the entire copper layer. Unfortunately, this means heat isn’t transmitted as easily to the entire copper layer. In high-power applications, like a connection to a heated bed, these thermals can heat up enough to melt a plastic connector. Once that happens, it’s game over.

Other problems were found in the Melzi board, although you wouldn’t know it just by looking at the Eagle file of the PCB. [Scott]’s Chinesium Melzi board used 1-ounce copper, where 2-ounce copper would be more appropriate. The connector, too, should be rated above the design power loading.

[Scott] made a few tweaks to the board and also added a tiny DS1822Z temperature sensor to the high-current area of his version of a Melzi. Imagine that, 3D printer electronics with a temperature sensor. Slowly but surely, the state of 3D printer electronics is clawing its way to the present.

Illuminating New Take on Magnetic Switches

While there’s something to be said for dead-bug construction, hot glue, and other construction methods that simply get the job done, it’s inspiring to see other builds that are refined and intentional but that still hack together things for purposes other than their original intent. To that end, [Li Zanwen] has designed an interesting new lamp that uses magnets to turn itself on in a way that seems like a magnetic switch of sorts, but not like any we’ve ever seen before.

While the lamp does use a magnetic switch, it’s not a traditional switch at all. There are two magnetic balls on this lamp attached by strings. One hangs from the top of the circular lamp and the other is connected to the bottom. When this magnet is brought close to the hanging magnet, the magnetic force is enough to both levitate the lower magnet, and pull down on a switch that’s hidden inside the lamp which turns it on. The frame of the lamp is unique in itself, as the lights are arranged on the inside of the frame to illuminate the floating magnets.

While we don’t typically feature design hacks, it’s good to see interesting takes on common things. After all, you never know what’s going to inspire your next hackathon robot, or your next parts drawer build. All it takes is one spark of inspiration to get your imagination going!