Fail Of The Week: How Not To Design An RF Signal Generator

September 6, 2018 by Dan Maloney 25 Comments

We usually reserve the honor of Fail of the Week for one of us – someone laboring at the bench who just couldn’t get it together, or perhaps someone who came perilously close to winning a Darwin Award. We generally don’t highlight commercial products in FotW, but in the case of this substandard RF signal generator, we’ll make an exception.

We suppose the fail-badge could be pinned on [electronupdate] for this one in a way; after all, he did shell out $200 for the RF Explorer signal generator, which touts coverage from 24 MHz to 6 GHz. But in true lemons-to-lemonade fashion, the video below he provides us with a thorough analysis of the unit’s performance and a teardown of the unit.

The first step is a look at the signal with a spectrum analyzer, which was not encouraging. Were the unit generating a pure sine wave as it should, we wouldn’t see the forest of spikes indicating harmonics across the band. The oscilloscope isn’t much better; the waveform is closer to a square wave than a sine. Under the hood, he found a PIC microcontroller and a MAX2870 frequency synthesizer, but a conspicuous absence of any RF filtering components, which explains how the output got so crusty. Granted, $200 is not a lot to spend compared to what a lab-grade signal generator with such a wide frequency range would cost. And sure, external filters could help. But for $200, it seems reasonable to expect at least some filtering.

We applaud [electronupdate] for taking one for the team here and providing some valuable tips on RF design dos and don’ts. We’re used to seeing him do teardowns of components, like this peek inside surface-mount inductors, but we like thoughtful reviews like this too.

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Ask Hackaday: Managing Inspiration

September 6, 2018 by Dan Maloney 65 Comments

For most of us, hacking is a hobby, something to pass a few idle hours and satisfy our need to create. Precious few of us get to live the dream of being paid to tinker; most of us need some kind of day job to pay the bills and support our hacking habits. This necessarily creates an essential conflict, rooted in the fact that we all only have 24 hours to spread around every day: I need to spend my time working so I can afford to hack, but the time I spend working to earn money eats away at my hacking time. That’s some catch, that Catch-22.

From that primary conflict emerges another one. Hacking is a hugely creative process, and while the artist or the author might not see it that way, it’s true nonetheless. Unless we’re straight-up copying someone else’s work, either because they’ve already solved the same problem we’re working on and we just need to get it done, or perhaps we’re just learning a new skill and want to stick to the script, chances are pretty good that we’re hitting the creative juices hard when we build something new. And that requires something perhaps even more limiting than time: inspiration. How you manage inspiration in large part dictates how productive you are in your creative pursuits.

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ZPB30A1 Electronic Load Gets An Open Firmware

September 6, 2018 by Tom Nardi 30 Comments

Importing cheap equipment and test gear is something of a mixed blessing. It allows you to outfit your lab without emptying your bank account, but on the other hand there’s usually a reason it’s cheap. Of course, the retail price of a piece of hardware shouldn’t be the metric by which we measure its quality, but there’s got to be a few corners cut someplace when they are selling this stuff for a fraction of what the name brands are charging.

A perfect example is the ZHIYU ZPB30A1 electronic load, available from various online importers for about $30 USD. While the price is right for an adjustable load that can handle up to 110 W, it’s got some pretty glaring shortcomings. In an effort to address at least some of those issues, [Luca Zimmermann] has been working on an open source replacement firmware for the load’s STM8S microcontroller.

[Luca] quickly discovered that the device’s STM8S005K6 chip is write protected, so unfortunately you can’t just flash a new firmware to it. If you want to unlock additional features, you need to perform a brain transplant. Luckily these chips are quite cheap, and you can probably add a couple of them to your cart when you order he ZPB30A1.

With the new GPLv3 licensed firmware installed, the device gains constant power and resistances modes (stock firmware can only do constant current), serial logging, and support for adjusting the value of the shunt resistor. There’s even a basic menu system to shuffle through the new modes. There’s still a couple features that haven’t been implemented, such as automatic shutdown, but it’s already a considerable upgrade from the stock software. Now we just need some details on the slick custom enclosure that [Luca] has put his upgraded ZPB30A1 into.

If this looks too easy, you can always go the DIY Arduino route for your load testing needs, or build a monster than can sink up to 1 kW.

[Thanks to Benik3 for the tip.]

Electromagnetic Field: A Hacked Knitting Machine, Knitting The Universe

September 6, 2018 by Jenny List 9 Comments

A large hacker camp attracts attendees from all over the world, and at the recent Electromagnetic Field in the UK there were certainly plenty of international visitors. Probably one of those with the longest journey was [Sarah Spencer] from Australia, and she deserves our admiration not just for her work but also for devoting much of her meagre luggage space to the installation she’d brought over for the event. In the lounge tent you could find the Knitted Universe, a map of the night sky with light-up Neopixel constellations covering an entire wall, and among the talks you could find her in-depth description of how she created it by hacking a 1980s Brother knitting machine into a network printer.

She starts with a potted history of knitting machine hacking, leading to the use of an emulated floppy drive replacing the mechanical item used to store scanned designs on the original hardware. She took an existing hack for a 16-bit Brother knitting machine and re-wrote it for her later 32-bit model, and then created a web interface for it called Octoknit which runs upon a Raspberry Pi. We’re then taken through the operation of a knitting machine and her further adventures in reverse engineering the file format. She ends up with a dithered 4-colour image, but there remains a problem. On the Brother, colour changes are performed by pressing a button, so something to automate the process was required. This task was taken on by her husband, who created an Arduino-driven mechanical button-presser in what had become a team effort. With this in place her only manual task became a periodic adjustment of the weight that preserves the tension in the finished knit.

Finally she moves on to the Knitted Universe itself, which at that point had become something of a viral sensation. Those of us who have created hacker camp installations will appreciate the volume of work that went into the piece, and she truly deserves the applause at the end of the talk. Watch it below the break, it’s a fascinating half-hour.

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