A Milliwatt Of DOOM

February 26, 2023 by Jenny List 36 Comments

The seminal 1993 first-person shooter from id Software, DOOM, has become well-known as a test of small computer platforms. We’ve seen it on embedded systems far and wide, but we doubt we’ve ever seen it consume as little power as it does on a specialized neural network processor. The chip in question is a Syntiant NDP200, and it’s designed to be the always-on component listening for the wake word or other trigger in an AI-enabled IoT device.

DOOM running on as little as a milliwatt of power makes for an impressive PR stunt at a trade show, but perhaps more interesting is that the chip isn’t simply running the game, it’s also playing it. As a neural network processor it contains the required smarts to learn how to play the game, and in the simple circular level it’s soon picking off the targets with ease.

We’ve not seen any projects using these chips as yet, which is hardly surprising given their niche marketplace. It is however worth noting that there is a development board for the lower-range sibling chip NDP101, which sells for around $35 USD. Super-low-power AI is within reach.

Rubber Bands And O-Rings Give 3D Prints Some Stretch

February 26, 2023 by Donald Papp 9 Comments

Sometimes it would be helpful if a 3D printed object could stretch & bend. Flexible filament like TPU is one option, but [NagyBig] designed a simple bracelet to ask: how about embedding rubber bands or o-rings into the print itself?

Embedding objects into prints usually involves hardware like fasteners or magnets, but this is the first one (we can think of) that uses rubber bands. Though we have seen rubber bracelets running on printed wheels, and o-rings used to provide tension on a tool holder.

The end result is slightly reminiscent of embedding 3D printed shapes into tulle in order to create fantastic, armor-like flexible creations. But using rubber bands means the result is stretchy and compliant to a degree we haven’t previously seen. Keep it in mind the next time you’re trying to solve a tricky design problem; an embedded o-ring or rubber band might just do the trick.

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Toroid Transformers Explained

February 24, 2023 by Al Williams 34 Comments

HF radios often use toroidal transformers and winding them is a rite of passage for many RF hackers. [David Casler, KE0OG] received a question about how they work and answered it in a recent video that you can see below.

Understanding how a conventional transformer works is reasonably simple, but toroids often seem mysterious because the thing that makes them beneficial is also what makes them confusing. The magnetic field for such a transformer is almost totally inside the “doughnut,” which means there is little interaction with the rest of the circuit, and the transformer can be very efficient.

The toroid itself is made of special material. They are usually formed from powdered iron oxide mixed with other metals such as cobalt, copper, nickel, manganese, and zinc bound with some sort of non-conducting binder like an epoxy. Ferrite cores have relatively low permeability, low saturation flux density, and low Curie temperature. The powder also reduces the generation of eddy currents, a source of loss in transformers. Their biggest advantage is their high electrical resistivity, which helps reduce the generation of eddy currents.

If you haven’t worked through how these common little transformers work, [David]’s talk should help you get a grip on them. These aren’t just for RF. You sometimes see them in power supplies that need to be efficient, too. If you are too lazy to wind your own, there’s always help.

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OpenStructures Is A Modular Building System For The RepRap Age

February 21, 2023 by Navarre Bartz 24 Comments

Modular construction toys like LEGO and Meccano are great for prototyping, but they aren’t so great for large builds. OpenStructures promises to be a modular building system for projects large and small.

Originally conceived in 2007 by [Thomas Lommée], OpenStructures is a modern, more robust reinterpretation of Grid Beam, which was itself a reinterpretation of the earlier Living Structures. By using a common standard (PDF), parts can be reused project after project as they would with LEGO, meaning you can spend more time building and less time cutting or figuring out joints. OpenStructures parts need connection points, part diameters, or part dimensions at multiples of 20 mm to be compatible. To fulfill the spirit of the project, parts should be designed for disassembly, use recyclable materials when possible, and be Open Source.

The system seems like a great starting point for prototyping furniture or other large builds more quickly than building everything on a case-by-case basis. By including diameters for round objects as well as square and rectangular profiles, OpenStructures is a more flexible (and aesthetically pleasing?) option than Grid Beam.

A couple more options for furniture-scale modular construction are these big LEGO bricks or copper pipe.

(via Low Tech Magazine)

Experimenting With 20 Meters Of Outlet Adapters

February 4, 2023 by Chris Lott 100 Comments

You may have seen some of the EEVblog dumpster dive videos, where [Dave Jones] occasionally finds perfectly good equipment that’s been tossed out. But this time, rather than a large screen monitor, desktop computer, or a photocopier, he features a stash of 283 electrical outlet double adapters that he found last year. He decided to perform a test in the parking lot, connecting all 283 adapters in series.

Using a pair of power meters and a 2 kW electric heater as a test load, [Dave] and his son [Sagan] measure the loss through this wild setup. It works out to about about 300 W, or roughly 1 W per adapter. He did a follow-up experiment using a FLIR thermal camera, and confirmed that the power loss is reasonably uniform, and that no single rogue adapter consuming all the lost power. After a back of the envelope calculation, we estimate this chain of adapters is about 20 meters long, making this whole thing entirely pointless but interesting nonetheless. Stick around until the end of the video for a teardown — they’re not as cheaply made as you might think.

[Dave]’s crazy experiment aside, we do wonder why someone had so many adapters to throw away in the first place. What would you have done with 283 adapters — left them in the dumpster or rescued them?

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Showing two MCP23017 expanders soldered onto a PCB

MCP23017 Went Through Shortage Hell, Lost Two Inputs

February 3, 2023 by Arya Voronova 68 Comments

The MCP23017, a 16-bit I2C GPIO expander, has always been a tasty chip. With 16 GPIOs addressable over I2C, proper push/pull outputs, software-enabled pull-ups, eight addresses, maskable interrupts for all pins, and reasonably low price, there’s a reason it’s so popular. No doubt due in part to that popularity, it’s been consistently out of stock during the past year and a half, as those of us unlucky enough to rely on it in our projects will testify.

Now, the chip is back in stock, with 23,000 of them to go around on Mouser alone, but there’s a catch. Apparently, the lengthy out-of-stock period has taken a heavy toll on the IC. Whether it’s the recession or perhaps the gas shortages, the gist is — the MCP23017 now a 14/16-bit expander, with two of the pins (GPA7 and GPB7) losing their input capabilities. The chips look the same, are called the same, and act mostly the same — if you don’t download the latest version of the datasheet (Revision D), you’d never know that there’s been a change. This kind of update is bound to cause a special kind of a debugging evening for a hobbyist, and makes the chip way less suitable for quite a few applications.

It’s baffling to think about such a change happening nearly 20 years after the chip was initially released, and we wonder what could have caused it. This applies to the I2C version specifically — the SPI counterpart, MCP23S17, stays unaffected. Perhaps, using a microcontroller or shift registers for your GPIO expansion isn’t as unattractive of an option after all. Microcontroller GPIO errata are at least expected to happen, and shift registers seem to have stayed the same since the dawn of time.

The reasons for MCP23017 silicon getting cut in such a way, we might never know. At least now, hopefully, this change will be less of a bitter surprise to those of us happy to just see the chip back in stock — and for hackers who have already restocked their MCP23017 hoards, may your shelved boards magically turn out to have a compatible pinout.

Brass Hardware Makes For Pretty Potentiometer Knobs

February 2, 2023 by Lewin Day 18 Comments

Knobs and switches can make or break the aesthetic and tactile appeal of a project. Fine hi-fi hardware goes hard on these details, while cheap knock-off guitar pedals often go the other way. If you’re looking for a unique, cheap, and compelling solution for potentiometer knobs, you might like to consider using converted brass hardware for the job.

The idea comes from [Kevin Jordan], who realized that some simple 3D printed parts would enable him to repurpose brass hardware for use with common split-shaft potentiometers. He grabbed a bunch of brass flare caps intended for use with gas piping, and got to work.

The result is the simple 3D printed cap converter. It has a threaded outer portion, which screws neatly inside a brass flare cap. Inside, it features a hole to mate to the potentiometer shaft. While this could be done with a spline, it also works with a simple hole since the plastic is soft enough to simply push the potentiometer shaft into.

The flare caps look great when pressed into service as knobs. [Kevin] uses them on a tennis racket guitar he built, and the brass knobs beautifully set off against the natural wood finishes of the build. If you’re looking for some unique adornments for your own projects, you might like to experiment with this concept yourself! Alternatively, you can try making your own knobs from scratch.

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