Next Weekend: Beginner Solar Workshop

June 28, 2018 by Brian Benchoff 5 Comments

Next week, Hackaday is hosting a workshop for all you hackers ready to harness the power of the sun. We’re doing a Beginner Solar Workshop at Noisebridge in San Francisco. You’re invited to join us on July 7th, we’ll provide the soldering irons.

The instructor for this workshop will be [Matt Arcidy], avid Hackaday reader and member of Noisebridge. He’s contributed to the incredible Noisebridge Gaming Archivists Live Arcade Cabinet, given talks on electronic components for the Arduino ecosystem, and now he’s hosting a workshop on the basics of solar charging.

This workshop will cover the theory of solar charging, how solar cells convert light into electricity, when and where this technology is appropriate, and the safe handling of lithium-ion batteries. At the end of the workshop, every attendee will have built a system that captures power from the sun and charges a battery, ready to be used in any future projects.

This is a big deal. Right now, the Hackaday Prize is in the middle of its third challenge, the Power Harvesting Module Challenge. This is a big part of the prize, and already there are some fascinating projects which harvest electricity from stomach acid, and even the gravitational potential of the Earth. Of course, some of those are more practical than others, and we’re really interested to see where this Power Harvesting Challenge goes and what great projects will be created.

3D Printed Tourniquets Are Not A Cinch

June 28, 2018 by Brian McEvoy 32 Comments

Saying that something is a cinch is a way of saying that it is easy. Modeling a thin handle with a hole through the middle seems like it would be a simple task accomplishable in a single afternoon and that includes the time to print a copy or two. We are here to tell you that is only the first task when making tourniquets for gunshot victims. Content warning: there are real pictures of severe trauma. Below, is a video of a training session with the tourniquets in Hayat Center in Gaza and has a simulated wound on a mannequin.

On the first pass, many things are done correctly: the handle is the correct length and diameter, the strap hole fit the strap, and the part is well oriented on the platen. As with many first iterations, it looks good on a screen, but in the real world, we all live under Murphy’s law. In practice, some of the strap holes had sharp edges that cut into the strap, and one of the printed buckles broke unexpectedly.

On the whole, the low cost and availability of the open-source tourniquets outweigh the danger of operating without them. Open-source medical devices are not just for use in the field, they can help with training too. This tourniquet is saving people and proving that modeling skills can be a big help in the real world.
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Move Aside Mercury: Measuring Temperature Accurately With An RTD

June 28, 2018 by Sean Boyce 40 Comments

Temperature is one of the most frequently measured physical quantities, and features prominently in many of our projects, from weather stations to 3D printers. Most commonly we’ll see thermistors, thermocouples, infrared sensors, or a dedicated IC used to measure temperature. It’s even possible to use only an ordinary diode, leading to some interesting techniques.

Often we only need to know the temperature within a degree Celsius or two, and any of these tools are fine. Until fairly recently, when we needed to know the temperature precisely, reliably, and over a wide range we used mercury thermometers. The devices themselves were marvels of instrumentation, but mercury is a hazardous substance, and since 2011 NIST will no longer calibrate mercury thermometers.

Luckily, resistance temperature detectors (RTDs) are an excellent alternative. These usually consist of very thin wires of pure platinum, and are identified by their resistance at 0 °C. For example, a Pt100 RTD has a resistance of 100 Ω at 0 °C.

An accuracy of +/- 0.15 °C at 0 °C is typical, but accuracies down to +/- 0.03 °C are available. The functional temperature range is typically quite high, with -70 °C to 200 °C being common, with some specialized probes working well over 900 °C.

It’s not uncommon for the lead wires on these probes to be a meter or more in length, and this can be a significant source of error. To account for this, you will see that RTD probes are sold in two, three, and four wire configurations. Two-wire configurations do not account for lead wire resistance, three-wire probes account for lead resistance but assume all lead wires have the same resistance, and four-wire configurations are most effective at eliminating this error.

In this article we’ll be using a 3-wire probe as it’s a good balance between cost, space, and accuracy. I found this detailed treatment of the differences between probe types useful in making this decision.

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Tiny Printers Get Color Mixing

June 28, 2018 by Brian Benchoff 8 Comments

Last weekend was the inaugural East Coast RepRap Festival in beautiful Bel Air, Maryland. Like it’s related con, the Midwest RepRap Festival, ERRF is held in the middle of nowhere, surrounded by farms, and is filled with only people who want to be there. It is the anti-Maker Faire; only the people who have cool stuff to show off, awesome prints, and the latest technology come to these RepRap Fests. This was the first ERRF, and we’re looking forward to next year, where it will surely be bigger and better.

One of the stand-out presenters at ERRF didn’t have a big printer. It didn’t have normal stepper motors. There weren’t Benchies or Marvins or whatever the standard test print is these days. [James] is showing off tiny printers. Half-scale printers. What’s half the size of a NEMA 17 stepper motor? A NEMA 8, apparently, something that isn’t actually a NEMA spec, and the two companies that make NEMA 8s have different bolt hole patterns. This is fun.

If these printers look familiar, you’re right. A few years ago at the New York Maker Faire, we checked out these tiny little printers, and they do, surprisingly, print. There are a lot of tricks to make a half-size printer, but the most impressive by far is the tiny control board. This tiny little board is just 2.5 by 1.5 inches — much smaller than the standard RAMPS or RAMBO you’d expect on a DIY printer. On the board are five stepper drivers, support for two heaters, headers for OLEDs and Graphic LCDs, and a switching regulator. It’s a feat of microelectronics that’s impressive and necessary for a half-size printer.

Since we last saw these tiny printers, [James] has been hard at work expanding what is possible with tiny printers. The most impressive feat from this year’s ERRF was a color-mixing printer built around the same electronics as the tiny printers. The setup uses normal-size stepper motors (can’t blame him) and a diamond-style hotend to theoretically print in three colors. If you’ve ever wanted a tiny printer, this is how you do it, and I assure you, they’re very, very cute.

Sunny Custom Keyboard Illuminates The Past

June 28, 2018 by Kristina Panos 35 Comments

Ever wonder why keyboard number pads and telephone dials have reversed layouts? Theories abound, but the most plausible one is that, shrug, it just happened that way. And now we’re stuck with it.

Well, that answer’s not good enough for [Jesse], so he punched up his own keyboard design that combines the golden years of function-rich Sun and IBM keyboards with Ma Bell’s DTMF number arrangement. That’s right, Sundial has 24 function keys total, and the number pad matches Ma Bell’s all the way down to the asterisk/zero/octothorpe pattern on the bottom row. How do we know what the unlabeled ones are, you ask? It’s all mapped out in this layout editor. We love that it has all the key lock indicator lights, because that practice should’ve never faded out in the first place.

Though inspired by this beautiful unicorn of an Arduino keyboard we covered a few months ago, the Sundial uses a Teensy 2.0 to translate [Jesse]’s Cherry MX clone-driven wishes into software commands. It’s also painstakingly hand-wired, so here’s the build log for you to drool over. Just cover up your keyboard first.

Raspberry Pi Tracks Starter Fermentation For Optimized Sourdough

June 27, 2018 by Dan Maloney 8 Comments

Those of you who’ve never had a real sourdough have never had real bread. Good food fights back a little when you eat it, and a proper sourdough, with its crispy crust and tangy center, certainly fits the bill. Sourdough aficionados, your humble writer included, all have recipes that we pretend are ancient family secrets while in reality we’re all just guessing. Sourdough is partly science, partly art, but mostly delicious black magic.

In an effort to demystify his sourdough process, [Justin Lam] has gone digital with this image processing sourdough starter monitor. Sourdough breads are leavened not by the addition of brewers yeast (Saccharomyces cerevisiae), but by the inclusion of a starter, a vibrant ecosystem of wild yeasts that is carefully nurtured, sometimes for years. Like any other living thing, it needs to be fed, a task that should happen at the point of maximum fermentation. Rather than guess when this might be, [Justin] used a Raspberry Pi Zero and PiCam to capture a time-lapse video of the starter as the beasties within give off their CO₂, thus expanding it up inside its container. A little Python does the work of thresholding and finding the top of the starter as it rises, allowing [Justin] to plot height of the starter over time. He found that peak height, and therefore peak fermentation, occurs about six hours after feeding. He has used his data to better inform his feeding schedule and to learn how best to revive neglected starters.

Surprisingly, this isn’t the first time we’ve discussed sourdough here. It seems that someone uses Git for iterative sourdough recipe development, and we once featured a foundry made from a pyrolyzed loaf of sourdough.

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Literary Camouflage For Your Router

June 27, 2018 by Brian McEvoy 39 Comments

What is suspicious about the books in the image above? Is it that there is no bookend? How about the radio waves pouring out of them? [Clay Weiland] does not like the way a bare router looks in the living room, but he appreciates the coverage gained by putting it in the middle of his house. He added a layer of home decorating camouflage in the form of some second-hand book covers to hide the unsightly bit of tech.

There isn’t a blog post or video about this particular build anywhere. The photos were submitted to our tip line as-is with the note that a table-saw is involved. We can safely infer that book covers are stripped of their pages and filled with wooden blanks painted white and stuck together to look like a cluster of literature. The takeaway from this example is that our tech does not have to be hidden away like a secret, or disrupt the decor, it can be placed as functionally as possible without sacrificing Feng Shui.