GPS? With Starlink, We Don’t Need It Any More!

October 10, 2021 by Jenny List 58 Comments

To find your position on the earth’s surface there are a variety of satellite-based navigation systems in orbit above us, and many receiver chipsets found in mobile phones and the like can use more than one of them. Should you not wish to be tied to a system produced by a national government though, there’s now an alternative. It comes not from an official source though, but as a side-effect of something else. Researchers at Ohio State University have used the Starlink satellite broadband constellation to derive positional fixing, achieving a claimed 8-metre accuracy.

The press release is light on information about the algorithm used, but since it mentions that it relies on having advance knowledge of the position and speed of each satellite we’re guessing that it measures the Doppler shift of each satellite’s signal during a pass to determine a relative position which can be refined by subsequent observations of other Starlink craft.

The most interesting takeaway is that while this technique leverages the Starlink network, it doesn’t have any connection to the service itself. Instead it’s an entirely passive use of the satellites, and though its accuracy is around an order of magnitude less than that achievable under GPS it delivers a position fix still useful enough to fit the purposes of plenty of users.

Earlier in the year there was some amusement when the British government bought a satellite broadband company under the reported impression it could plug the gap left by their withdrawal from the European Galileo project. Given this revelation, maybe they were onto something after all!

Thanks [Renze] for the tip.

A Bike Trailer For Any Expedition

October 10, 2021 by Jenny List 30 Comments

One of the greatest challenges for a hardware hacker relying only on a bicycle for transport lies in the regular need to carry more than can be slung from the handlebars or on the luggage rack of your trusty steed. One of our favourite YouTube creators in our sphere, [Laura Kampf], has addressed this problem with a trailer for her electric bike made from a pair of second-hand wheelbarrows. She uses their buckets to make a clamshell box, and their wheels alongside a custom steel chassis to make the rest of the trailer.

As always with Laura’s work it’s a delight to watch, with some careful use of the cutting wheel to install hinges and vents in the upper bucket. Finishing touches are a chequer plate top for the trailer and a spare wheel mounted on the back for that extra-rugged look. Experience with wheelbarrow wheels suggests to us that the slightly more expensive ones with ball bearings are worth the investment over the plastic ones, but either way this is a bike trailer that means business.

We don’t see as many bike trailers as we’d like here at Hackaday, and those few we have are old enough to have succumbed to link-rot. Perhaps this project might tempt a few people to try their hand?

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1981 Called, Here’s Your Software

October 10, 2021 by Jenny List 53 Comments

How many of us who have a few decades of adulthood under our belts would like to talk to our 17 year old selves? “Hey kid, it’s all gonna be OK. Also, Duke Nukem Forever does come out eventually, but it’s not going to be pretty!” Being honest, exposure to the hot takes of one’s naive teenage self would almost certainly be as cringeworthy as the time-worn-but-familiar adult would be to the teenager, but there’s one way in which you can in a sense have a conversation with your teenage self. [Mad Ned] had this opportunity, when he discovered a printed BASIC listing for a game he’d written for the TRS-80 back in 1981. Could he make it run again, and what did it tell him about his teenage years?

Grizzled 8-bit veterans will tell you of countless hours spent typing poorly-reproduced listings found in magazines, and the inevitable pain that followed as all those mistypes were ironed out. [Ned] eschewed all that retro experience because this is the 21st century, and we now have much more powerful computers to do our bidding! The reality of incomplete OCR is one we’ll no doubt all be used to, and for 8-bit fans also the debugging that was needed to get the listing to run. Breaker Ball is an odd hybrid of Breakout and Space Invaders, and it’s his analysis of the teenage thinking that led to the game being the way it is that rounds off the piece. Sadly we’re not treated to the entire listing, but there’s a short gameplay video we’ve placed below the break.

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Drive High-Impedance Headphones With This Stylish USB DAC

October 9, 2021 by Jenny List 3 Comments

For anyone with an interest in building audio projects, it’s likely that an early project will be a headphone amplifier. They’re relatively easy to build from transistors, ICs, or tubes, and it’s possible to build one to a decent quality without being an electronic engineering genius. It’s not often though that we see one as miniaturized as [daumemo]’s USB-C DAC and headphone amplifier combo, that fits within a slightly elongated 3.5 mm jack cover as part of a small USB-to-headphone cable.

The DAC is an off-the-shelf board featuring an ALC4042 IC, it has a line-level output and a handy place to tap off a 5 volt line for the amplifier. This final part is a tiny PCB with two chips, a TPS65135 that produces clean +5 and -5 volt rails, and an INA1620 which is a high-quality audio amplifier set up for 2x gain. All this has been designed onto a very small PCB, which sits inside a 3D-printed housing along with the 3.5 mm earphone socket. The result is a very neat unit far better able do drive high-impedance headphones than the output from an unmodified DAC, but still looking as svelte as any commercial product. We like it.

This may be one of the most compact USB-to-headphone amplifiers we’ve seen, but it’s by no means the first.

Making Coffee With Hydrogen

October 9, 2021 by Jenny List 17 Comments

Something of a Holy Grail among engineers with an interest in a low-carbon future is the idea of replacing fossil fuel gasses with hydrogen. There are various schemes, but they all suffer from the problem that hydrogen is difficult stuff to store or transport. It’s not easily liquefied, and the tiny size of its molecule means that many containment materials that are fine for methane simply won’t hold on to it.

[Isographer] has an idea: to transport the energy not as hydrogen but as metallic aluminium, and generate hydrogen by reaction with aqueous sodium hydroxide. He’s demonstrated it by generating enough hydrogen to make a cup of coffee, as you can see in the video below the break.

It’s obviously very successful, but how does it stack up from a green perspective? The feedstocks are aluminium and sodium hydroxide, and aside from the hydrogen it produces sodium aluminate. Aluminium is produced by electrolysis of molten bauxite and uses vast amounts of energy to produce, but since it is often most economic to do so using hydroelectric power then it can be a zero-carbon store of energy. Sodium hydroxide is also produced by an electrolytic process, this time using brine as the feedstock, so it also has the potential to be produced with low-carbon electricity. Meanwhile the sodium aluminate solution is a cisutic base, but one that readily degrades to inert aluminium oxide and hydroxide in the environment. So while it can’t be guaranteed that the feedstock he’s using is low-carbon, it’s certainly a possibility.

So given scrap aluminium and an assortment of jars it’s possible to make a cup of hot coffee. It’s pretty obvious that this technology won’t be used in the home in this way, but does that make it useless? It’s not difficult to imagine energy being transported over distances as heavy-but-harmless aluminium metal, and we’re already seeing a different chemistry with the same goal being used to power vehicles.

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Nifty Chip Adapter Does The Impossible

October 9, 2021 by Jenny List 30 Comments

The semiconductor shortage has curtailed the choices available to designers and caused some inventive solutions to be found, but the one used by [djzc] is probably the most inventive we’ve yet seen. The footprint trap, when a board is designed for one footprint but shortages mean the part is only available in another, has caught out many an engineer this year. In this case an FTDI chip had been designed with a PCB footprint for a QFN package when the only chip to be found was a QFP from a breakout board.

The three boards which make up the adaptor — The three boards which make up the adapter

For those unfamiliar with semiconductor packaging, a QFN and QFP share a very similar epoxy package, but the QFN has its pins on the underside flush with the epoxy and the QFP has them splayed out sideways. A QFP is relatively straightforward to hand-solder so it’s likely we’ll have seen more of them than QFNs on these pages.

There is no chance for a QFP to be soldered directly to a QFN footprint, so what’s to be done? The solution is an extremely inventive one, a two-PCB sandwich bridging the two. A lower PCB is made of thick material and mirrors the QFN footprint above the level of the surrounding components, while the upper one has the QFN on its lower side and a QFP on its upper. When they are joined together they form an inverted top-hat structure with a QFN footprint below and a QFP footprint on top. Difficult to solder in place, but the result is a QFP footprint to which the chip can be attached. We like it, it’s much more elegant than elite dead-bug soldering!

This Audio Mixer Is A Eurorack

October 4, 2021 by Jenny List 14 Comments

Music making and DJing have both become arts predominantly pursued in a computer, as the mighty USB interface has subsumed audio, MIDI, and even DJ turntable interface controllers. There was a time though when an indispensable part of any aspiring performer’s equipment would have been an analog mixer, a device for buffering and combining multiple analog audio signals into a single whole. A mixer is still a useful device though, and [Sam Kent] has produced a very nice one that takes the form of a set of Eurorack modules made from PCB material. There are two types of modules, the main channel module which you can think of as the master module, and a series of isolator modules that handle the individual inputs.

Mixer preferences are as individual as each user, so for example where we’d expect sliders he’s used rotary potentiometers, and for us placing the master channel on the left-hand side is unfamiliar. But that’s the beauty of a modular design, there’s nothing to stop anyone building one of these to simply configure it as they wish. We notice that for a mixer described as for DJs there’s no RIAA preamp for the turntable fans, but it’s not impossible to fix with an off-board preamp. Otherwise, we like it and have a sudden hankering for it to be 1992 again with a pair of Technics SL1200s and a room full of people.

Designing a mixer, even a simple one, isn’t easy. Our own [Lewin Day] wrote a retrospective of his experiences with one.