Watch This Tiny Dome Auto-open And Close Into A Propeller

March 30, 2018 by 16 Comments

Careful planning and simulation is invaluable, but it can also be rewarding to dive directly into prototyping. This is the approach [Carl Bugeja] took with his Spherical Folding Propeller design which he has entered into the Open Hardware Design Challenge category of The 2018 Hackaday Prize. While at rest, the folding propeller looks like a small dome attached to the top of a motor. As the motor fires up, centrifugal forces cause the two main halves of the dome to unfold outward where they act as propeller blades. When the motor stops, the assembly snaps shut again.

[Carl] has done some initial tests with his first prototype attached to a digital scale as a way of measuring thrust. The test unit isn’t large — the dome is only 1.6 cm in diameter when folded — but he feels the results are promising considering the small size of the props and the fact that no simulation work was done during the initial design. [Carl] is looking to optimize the actual thrust that can be delivered, now that it has been shown that his idea of a folding dome works as imagined.

Going straight to physical prototyping with an idea can be a valid approach to early development, especially nowadays when high quality components and technologies are easily available even to hobbyists. Plus it can be great fun! You can see and hear [Carl]’s prototype in the short video embedded below.

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Fail Of The Week: How Not To Build Your Own DGPS Base Station

March 30, 2018 by 79 Comments

GPS is the modern answer to the ancient question about one’s place in the world yet it has its limitations. It depends on the time of flight of radio signals emitted by satellites twenty thousand kilometers above you. Like any system involving large distances and high velocities, this is bound to offer some challenges to precise measurements which result in a limit to achievable accuracy. In other words: The fact that GPS locations tend to be off by a few meters is rooted in the underlying principle of operation.

Today’s level of precision was virtually unattainable just decades ago, and we’re getting that precision with a handheld device in mere seconds. Incredible! Yet the goal posts continue to move and people are working to get rid of the remaining error. The solution is called Differential GPS or ‘DGPS’ and its concept looks surprisingly simple.

What’s fascinating is that you can use one GPS to precisely measure the error of another GPS. This is because the inherent error of a GPS fix is known to be locally constant. Two receivers next to each other pick up signals that have been affected in the same way and thus can be expected to calculate identical wrong positions. This holds true for distances up to several kilometers between individual receivers. So in order to remove the error, all you need is a GPS receiver in a known location to measure the current deviation and a way to transmit correction information to other units. DGPS does just that, using either terrestrial radio in some regions and satellites in others. Mobile solutions exist as well.

So a raspi with a USB GPS dongle in a known location should be able to act as a DGPS over IP base station, right? In theory, yes. In practice… fail.

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Learn What Did And Didn’t Work In This Prototyping Post-Mortem

March 30, 2018 by 16 Comments

[Tommy] is a one-man-shop making electronic musical things, but that’s not what this post is about. This post is about the outstanding prototyping post-mortem he wrote up about his attempt to turn his Four-Step Octaved Sequencer into a viable product. [Tommy] had originally made a hand-soldered one-off whose performance belied its simple innards, and decided to try to turn it into a product. Short version: he says that someday there will be some kind of sequencer product like it available from him, “[B]ut it won’t be this one. This one will go on my shelf as a reminder of how far I’ve come.”

The unit works, looks great, has a simple parts list, and the bill of materials is low in cost. So what’s the problem? What happened is that through prototyping, [Tommy] learned that his design will need many changes before it can be used to create a product, and he wrote up everything he learned during the process. Embedded below is a demo of the prototype that shows off how it works and what it can do, and it helps give context to the lessons [Tommy] shares.

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Color Spaces: The Model At The End Of The Rainbow

March 30, 2018 by 23 Comments

When I learned about colors in grade school everything started with red, yellow, and blue and getting fancier colors was easy. I mixed some blue into my yellow to get green, or into red to get purple, and so on. After painting enough terrifying “art” for my parents, this made intuitive sense. That is until my mind was blown by the revelation that this wasn’t always true! 

To make the same colors with light instead of paint I had to use red, green, and blue, not yellow. It was until much later when trying harness banks of RGB LEDs that this knowledge became useful. I was struggling to make my rogue diodes look quite the way I wanted when I stumbled into the realization that maybe there was another approach. What did the numbers representing R G and B actually mean? Why those parameters? Could there be others? [Elliot Williams] has written about the importance of gamma correction and adjustment for human perception of color, but we can ask a more fundamental question. Why do we represent color this way at all?

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Oracle V Google Could Chill Software Development

March 30, 2018 by 96 Comments

Unless you’ve completely unplugged from the news, you probably are aware that the long-running feud between Oracle and Google had a new court decision this week. An appeal court found that Google’s excuse of fair use wasn’t acceptable and that they did infringe on Oracle’s copyrights to Java. Oracle has asked for about $9 billion in damages, although the actual amount is yet to be decided. In addition, it is pretty likely Google will take it up to the Supreme Court before any actual judgment is levied.

The news is aimed at normal people, so it is pretty glossy about what exactly happened. We set out to try to make sense of it all. We found a pretty good article from [Michaela Barry] about what the courts previously found.  There were three main parts:

  • There were 37 API (Application Programming Interface) declarations taken verbatim from Java. This would be like a C header file if you aren’t familiar with Java.
  • Google decompiled 8 security files and used them.
  • The rangeCheck function — 9 lines of Java code — were exactly the same in Oracle’s Java and Android.

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This Is How The Fonz Would Play MP3s

March 30, 2018 by 10 Comments

Here at Hackaday, we love to see old hardware treated with respect. A lovingly restored radio or TV that’s part of our electronic heritage is a joy to behold, and while we understand the desire to stream media from a funky retro case, it really grates when someone throws away the original guts to make room for new electronics.

Luckily, this Seeburg jukebox wall remote repurposing is not one of those projects. [Scott M. Baker] seems to have an appreciation for the finer things, and when he scored this classic piece of Mid-Century Americana, he knew just what to do. These remotes were situated around diners and other hangouts in the 50s and 60s and allowed patrons to cue up some music without ever leaving their seats. They were real money makers back in the day, and companies put a lot of effort into making them robust and reliable.

[Scott]’s first video below shows the teardown of this unit; you can practically smell the old transformer and motor windings. His goal in the second video was to use the remote to control his Raspberry Pi jukebox; he wisely decided to leave everything intact and use the original electromechanically generated pulses to make selections. His analysis led to a nicely executed shield for his Pi which conditions the pulses and imitates coin drops; happily, the coin mechanism still works too, so you can still drop a quarter for a tune.

The remote is working well now, but [Scott] still needs to finish up a few odds and ends to bring this one home. But we love the look and the respect for tradition here, as we did when this juke got a Raspberry Pi upgrade to imitate a missing wall remote.

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Apple One, On FPGA

March 29, 2018 by 17 Comments

Today, Apple is known for iPhones, iPads, and a commitment to graphical user interfaces. But that wasn’t how it all started. The original Apple was a single board computer built around a 6502. In 1976, you could snag one for $666.66, but you needed to supply your own TV, power supply, and keyboard. [Alangarf] didn’t have an Apple 1, but he did have a 6502 CPU core for FPGAs from [Andrew Holme] that he fleshed out to an Apple I clone with a VGA output and PS/2 keyboard port. The project works with either an iCE40 board or a Terasic DE0 board. You could probably port it to other similar FPGAs.

This is much more practical than trying to find an original, as Apple bought a lot of the old boards back and destroyed them. According to the Apple-1 Registry there are only about 71 of the boards still in existence, and that’s with the annotation that 4 of those may be lost and 8 might be duplicates. We’ve heard that of those there are only six that actually still work.

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