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.

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.

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.

[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.

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.

If there’s one thing audiences love in sci-fi, it’s a cute robot companion that follows the heroes around. If you want one of your own, starting with this build from [mircemk] could be just the ticket.

The build relies on the classic Arduino Uno microcontroller, which talks to a HC-SR04 ultrasonic sensor module and two infrared sensors in order to track a human target and follow it around. Drive is thanks to four DC gear motors, driven by a L293D motor driver, with a two-cell lithium battery providing power for everything onboard.

The robot works in a simple manner, following a hand placed in front of the robot’s sensors. First, the robot checks for the presence of an object in front using the ultrasonic sensor. If something is detected, the twin infrared sensors mounted left and right are used to guide the robot, following the hand.

It’s not a sophisticated algorithm, and it won’t really let your robot follow you down a crowded street. However, it’s a great project to learn on for beginners and could serve as a great entry into more advanced projects using face tracking or other techniques. Video after the break.

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.

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.

Thanks to [morgan] for the tip!

Building a clock from parts is a right of passage for makers, and often represents a sensible introduction into the world of electronics. It’s also hard to beat the warm glow of Nixie tubes in a desktop clock, as [Joshua Coleman] discovered when building a Nixie tube clock for a friend.

The original decision to upcycle the chassis from an unrepairable Heathkit function generator came a little undone after some misaligned cutting, so the front panel ended up being redesigned and 3D printed. This ended up being serendipitous, as the redesigned front panel allowed the Nixie tubes to be inset within the metal chassis. This effect looks great, and it also better protects the tubes from impact damage.

Sourcing clones of the 74141 Nixie driver ICs ended up being easier than anticipated, and the rest of the electronics came together quickly. The decoders are driven by an Arduino, and the IN-4 Nixie tubes are powered by a bespoke 170 volt DC power supply.

Unfortunately four of the tubes were damaged during installation, however replacements were readily available online. The gorgeous IN-4 Nixie tube has a reputation for breaking easily, but is priced accordingly on auction sites and relatively easy to source.

The build video after the break should get any aspiring Nixie clock makers started, but the video description is also full of extra information and links for those needing help getting started.

We’re not short on clock hacks here at Hackaday, so why not check out a couple more? This retro-inspired LED clock looks like its right out of a parallel universe, or maybe this stunning Nixie clock driven by relays will strike your fancy.

From the smallest 60% keyboards for those with no desk space to keyboards with number pads for those doing data entry all day, there’s a keyboard size and shape for just about everyone. The only problem, even with the largest keyboards, is that they’re still fairly limited in what they can do. If you find yourself wishing for even more functionality, you might want to build something like this custom macro keyboard with built-in LED backlighting.

Rather than go with a standard mechanical keyboard switch like a Cherry MX, this build is based around TS26-2 pushbuttons with built-in LED lighting. [atkaper] only really needed one button for managing the mute button on MS Teams, but still built a total of eight switches into this keyboard which can all be individually programmed with different functions. The controller is an Arduino Leonardo and the enclosure was 3D printed.

Paired with the classic IBM Model M keyboard, this new macro keyboard adds plenty of functionality while also having control over LED backlighting. Macro keyboards are incredibly useful, especially with their ability to easily change function with control over the software that runs on them. The key to most builds is the 32U4 chip found in some Atmel microcontrollers which allows it to easily pass keyboard (and mouse) functionality to any computer its plugged in to.

From the smallest 60% keyboards for those with no desk space to keyboards with number pads for those doing data entry all day, there’s a keyboard size and shape for just about everyone. The only problem, even with the largest keyboards, is that they’re still fairly limited in what they can do. If you find yourself wishing for even more functionality, you might want to build something like this custom macro keyboard with built-in LED backlighting.

Rather than go with a standard mechanical keyboard switch like a Cherry MX, this build is based around TS26-2 pushbuttons with built-in LED lighting. [atkaper] only really needed one button for managing the mute button on MS Teams, but still built a total of eight switches into this keyboard which can all be individually programmed with different functions. The controller is an Arduino Leonardo and the enclosure was 3D printed.

Paired with the classic IBM Model M keyboard, this new macro keyboard adds plenty of functionality while also having control over LED backlighting. Macro keyboards are incredibly useful, especially with their ability to easily change function with control over the software that runs on them. The key to most builds is the 32U4 chip found in some Atmel microcontrollers which allows it to easily pass keyboard (and mouse) functionality to any computer its plugged in to.

We enjoy access to cheap stuff because of the mass market for things like mice, keyboards, and cell phones. But if you need a device that doesn’t have mass appeal, you will have to pay a lot more if you can find it at all. However, with modern techniques like 3D printing and Arduino-like microcontrollers being cheap and simple to use, you now have the option to build that special one-of-a-kind device. Case in point: [Davy’s] mouse for people who have brain or nervous system disorders. This particular device is helping a 6-year-old who can’t manipulate a normal mouse.

The device uses an Arduino Pro and an MPU-6050 accelerometer and gyroscope. The original design uses machined aluminum, but 3D printing should work, too. There’s something wrong with the link to the design files in the post, but it is easy to find the correct link.

If you do 3D print a similar enclosure, you might consider using heat-set threaded inserts instead of tapping the holes. They work great, are easy to install, and seem to be a bit more robust than trying to thread plastic. Then again, threaded plastic isn’t as bad as you might think.

There are, of course, many ways you could make this work, and besides, every special user will be a little different. But what a great feeling to help someone be able to do what most people take for granted.