Edible Electronics Let Us Hear The Lamentations Of The Chocolate Bunnies

April 19, 2022 by Kristina Panos 12 Comments

Yet another Day of the Chocolate Bunnies has passed by, and what did you do to mark the occasion? You likely kicked back and relaxed, surrounded by whatever you gave up for Lent, but good for you if you mixed chocolate and electronics like [Repeated Failure] did. They created a completely edible chocolate Easter bunny that screams when bitten.

So obviously, the hardest part is figuring out something to build the circuit with that is both conductive and safe to eat. [Repeated Failure] spent a lot of time with carbon oleogel paste, which is made from natural oils and waxes. Not only was it less conductive than [Repeated Failure]’s skin, it came out pitch black and tasted like nothing, which kind of a bonus, when you think about it.

Then came the cake paint, which [Repeated Failure] laced with trace amounts of silver powder. While that worked somewhat better, a successful circuit would have likely required near-fatal amounts of the stuff. Yikes!

The winner turned out to be edible silver leaf, which is like gold leaf but cheaper. Ever had Goldschläger? Gold leaf is what’s suspended inside. The really nice thing about silver leaf is that it comes in thin sheets and can easily be cut into circuit traces with scissors and connected to I/O pins with copper tape. Be sure to check it out after the break, including [Repeated Failure]’s friend’s reaction to innocently biting the chocolate bunny’s ears off, as one tends to do first.

Think you’d rather hear plants giggle? Sure, it sounds cute, but it’s actually kind of creepy.

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Paper Tape Reader Self-calibrates, Speaks USB

April 16, 2022 by Donald Papp 22 Comments

Input devices consisting of optical readers for punched paper tape have been around since the earliest days of computing, so why stop now? [Jürgen]’s Paper Tape Reader project connects to any modern computer over USB, acting like a serial communications device. Thanks to the device’s automatic calibration, it works with a variety of paper materials. As for reading speed, it’s pretty much only limited to how fast one can pull tape through without damaging it.

Stacked 1.6 mm PCBs act as an enclosure, of sorts.

While [Jürgen]’s device uses LEDs and phototransistors to detect the presence or absence of punched holes, it doesn’t rely on hardware calibration. Instead, the device takes analog readings of each phototransistor, and uses software-adjusted thresholds to differentiate ones from zeros. This allows it to easily deal with a wide variety of tape types and colors, even working with translucent materials. Reading 500 characters per second isn’t a problem if the device has had a chance to calibrate.

Interested in making your own? The build section of the project has all the design files; it uses only through-hole components, and since the device is constructed from a stack of 1.6 mm thick PCBs, there’s no separate enclosure needed.

Paper tape and readers have a certain charm to them. Cyphercon 4.0 badges featured tape readers, and we’ve even seen the unusual approach of encoding an I²C byte stream directly onto tape.

This DIY UPDI Programmer Is Nice And Cheap

April 15, 2022 by Donald Papp 3 Comments

[Daumemo] likes experimenting with DIY electronics, and like many people, eventually ran across an AVR microcontroller with a Unified Program and Debug Interface (UPDI). One option is of course to purchase an UPDI programmer, but an even better solution was to make a DIY USB version from nice, cheap parts.

Programming an Attiny404 over the UPDI interface.

UPDI is an interface for external programming and on-chip debugging of microcontrollers, and [Daumemo]’s solution is based on the jtag2updi project. It combines an Arduino Nano (in this case, a clone) with a single resistor, a single capacitor, and a six pin angled header (with a cleverly bent pin) to enable programming UPDI devices over a USB connection. [Daumemo] is happy to report that the device works just fine in both Microchip Studio with AVRDUDE, or PlatformIO.

Is an Arduino Nano a bit overpowered in this role? Maybe, but the price is certainly right. There’s no need for a custom PCB either, since everything can be soldered direct to the Nano board. A matching 3D printed enclosure is about all that’s needed to make a robust and reliable DIY USB UPDI programmer out of a handful of parts, and that sounds good to us.

On the other hand, if you do find yourself making custom PCBs, you may be interested in another of [Daumemo]’s DIY projects: a printable structure to turn a rotary tool into a PCB drill press.

Coin Acceptors Are Higher-Tech Than You Think

April 10, 2022 by Al Williams 16 Comments

Coin-operated machines have a longer history than you might think. Ancient temples used them to dispense, for example, holy water to the faithful in return for their coins. Old payphones rang a bell when you inserted a coin so the operator knew you paid. Old pinball machines had a wire to catch things with holes in the middle so you couldn’t play with washers. But like everything else, coin acceptors have advanced quite a bit. [Electronoobs] shows a unit that can accept coins from different countries and it is surprisingly complex inside. He used what he learned from the teardown to build his own Arduino-based version.

For scale, there is the obligatory banana. Inside the box there are several induction coils and some photo electronics. In particular, there are two optical sensors that watch the coin roll down a ramp. This produces two pulses. The width of the pulse indicates the diameter of the coin, and the time between the pulses tells its speed.

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CAT Is Not Your Average Meow-cropad

April 9, 2022 by Kristina Panos 3 Comments

Are you completely over the idea of the keyboard in any flattish form and looking for something completely different for inputting your data? Or do you want a mega macropad for 3D design, GIMP or Inkscape work, or to use while relaxing with a nice first-person shooter? Then this ergonomic, double-fistable keyboard/controller mashup named CAT may be what you’re looking for.

Inside each of these slinky felines is pretty much what you’d expect to find — 25 or so switches and an Arduino Pro Micro. Interestingly enough, the switches are all lever-action and not push buttons. There are two breeds of CAT available to build or buy: one has 25 buttons, and the other has a joystick or trackball on the thumb between two upper and two lower buttons. You could have one type for each hand!

More information is available on the Lynx Workshop site, which is where you’ll also find tutorials and instructions for everything from the 3D printing to the electronics to the assembly and coding. There is even a bonus 3D modeling tutorial. Don’t want to invest the time to make your own CAT? These kitties are also available for pre-order. Claw past the break to check them out in action.

Looking for something with regular keyswitches? Oh, we have plenty of those.

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A Bargain In Bionic Knees

April 8, 2022 by Al Williams 17 Comments

You probably don’t want to lose a leg, but if you have to there are many options now that were unthinkable not long ago. That is, if you can afford them. A microprocessor knee — a prosthetic with some smarts in it — can run anywhere from $25,000 to well over $100,000. However [Lucas Galey], a PhD candidate at the University of Texas El Paso in a recent paper claims to be able to produce a comparable artificial knee for under $1,000. If the paper is too long to read, Amplitude has a good summary including what it means to people who need them.

Of course, the cost of making something like this is almost incidental. The cost of approvals, testing, and other factors mean that even with about $500 in parts, the retail price would be much higher. Probably not $25,000, though.

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Stress-Testing An Arduino’s EEPROM

April 7, 2022 by Bryan Cockfield 29 Comments

Every time one of us flashes an Arduino’s internal memory, a nagging thought in the backs of our minds reminds us that, although everything in life is impermanent, nonvolatile re-writable memory is even more temporary. With a fixed number of writes until any EEPROM module fails, are we wasting writes every time we upload code with a mistake? The short answer is that most of us shouldn’t really be concerned with this unless we do what [AnotherMaker] has done and continually write data until the memory in an Arduino finally fails.

The software for this is fairly simple. He simply writes the first 256 ints with all zeros, reads them to make sure they are all there, and then repeats the process with ones. After iterating this for literally millions of times continuously over the course of about a month he was finally able to get his first read failure. Further writes past this point only accelerated the demise of the memory module. With this method he was able to get nearly three million writes before the device failed, which is far beyond the tens or hundreds of thousands typically estimated for a device of this type.

To prove this wasn’t an outlier, [AnotherMaker] repeated the test, and did a few others while writing to a much smaller amount of memory. With this he was able to push the number of cycles to over five million. Assuming the Arduino Nano clone isn’t using an amazingly high-quality EEPROM we can safely assume that most of us have nothing to worry about and our Arduinos will be functional for decades to come. Unless a bad Windows driver accidentally bricks your device.

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