Spot This DIY Electronic Load’s Gracefully Hidden Hacks

February 28, 2019 by Donald Papp 11 Comments

Sometimes it’s necessary to make do with whatever parts one has on hand, but the results of squashing a square peg into a round hole are not always as elegant as [Juan Gg]’s programmable DC load with rotary encoder. [Juan] took a design for a programmable DC load and made it his own in quite a few different ways, including a slick 3D-printed enclosure and color faceplate.

The first thing to catch one’s eye might be that leftmost seven-segment digit. There is a simple reason it doesn’t match its neighbors: [Juan] had to use what he had available, and that meant a mismatched digit. Fortunately, 3D printing one’s own enclosure meant it could be gracefully worked into the design, instead of getting a Dremel or utility knife involved. The next is a bit less obvious: the display lacked a decimal point in the second digit position, so an LED tucked in underneath does the job. Finally, the knob on the right could reasonably be thought to be a rotary encoder, but it’s actually connected to a small DC motor. By biasing the motor with a small DC voltage applied to one lead and reading the resulting voltage from the other, the knob’s speed and direction can be detected, doing a serviceable job as rotary encoder substitute.

The project’s GitHub repository contains the Arduino code for [Juan]’s project, which has its roots in a design EEVblog detailed for an electronic load. For those of you who prefer your DIY rotary encoders to send discrete clicks and pulses instead of an analog voltage, a 3D printed wheel and two microswitches will do the job.

The No-Parts Temperature Sensor In Your Arduino

February 26, 2019 by Brian Benchoff 25 Comments

[Edward], creator of the Cave Pearl project, an underwater data logger, needed a way to measure temperature with a microcontroller. Normally, this problem is most easily solved by throwing a temperature sensor on the I2C bus — these sensors are cheap and readily available. This isn’t about connecting a temperature sensor in your Arduino. This build is about using the temperature sensor in your clock.

The ATMega328p, the chip at the heart of all your Arduino Uno clones, has within it a watchdog timer that clicks over at a rate of 110 kHz. This watchdog timer is somewhat sensitive to temperature, and by measuring this temperature sensor you can get some idea of the temperature of the epoxy blob that is a modern microcontroller. The trick is calibrating the watchdog timer, which was done with a homemade ‘calibration box’ in a freezer consisting of two very heavy ceramic pots with a bag of rice between them to add thermal mass (you can’t do this with water because you’re putting it in a freezer and antique crocks are somewhat valuable).

By repeatedly taking the microcontroller through a couple of freeze-thaw cycles, [Edward] was able to calibrate this watchdog timer to a resolution of about 0.0025°C, which is more than enough for just about any sensor application. Discussions of accuracy and precision notwithstanding, it’s pretty good.

This technique measures the temperature of the microcontroller with an accuracy of 0.005°C or better, and it’s using it with just the interrupt timer. That’s not to say this is the only way to measure the temperature of an ATMega; some of these chips have temperature sensors built right into them, and we’ve seen projects that use this before. However, this documented feature that’s clearly in the datasheet seems not to be used by many people.

Thanks [jan] for sending this in.

FPGA Brings Arduboy To The Game Boy Advance

February 21, 2019 by Tom Nardi 8 Comments

Hackaday readers are perhaps familiar with the Arduboy, an open source handheld gaming system that aims to combine the ease of Arduino development with the seething nostalgia the Internet has towards the original Nintendo Game Boy. While not quite the same as getting one of your games published for a “real” system, the open source nature of the Arduboy platform allows an individual to develop a game playable on a commercially manufactured device.

While the Arduboy hardware itself is actually quite slick, that hasn’t stopped people from trying to bring its games to other pieces of hardware. Now thanks to the efforts of [uXe], the Game Boy Advance is well on its way to becoming Arduboy compatible, in a way bringing the whole project full circle. Assuming this gadget becomes a commercial device (it sounds like that’s still up in the air), Arduboy developers will be able to proudly play their creations on the final and objectively best entry into the Game Boy line.

Getting to this point has been something of an adventure, as documented in a thread from the Arduboy forums. Members of the community wondered what it would take to get Arduboy games running on a real Game Boy, but pretty quickly it was decided that the original beige brick model wasn’t quite up to the task. Eventually its far more capable successor the Game Boy Advance became the development target, and different approaches were considered for getting existing games running on the platform.

While there were some interesting ideas, such as using the GBA’s link port to “feed” the system games over SPI, in the end [uXe] decided to look into creating an FPGA cartridge that would actually run the Arduboy games. In this scenario, the GBA itself is basically just being used as an interface between the FPGA and the human player. In addition to these low-level hardware considerations, there was considerable discussion about the more practical aspects of bringing the games to the new hardware, such as how to best scale the Arduboy’s 128 x 64 output to the GBA’s 240 × 160 screen.

As demonstrated in the videos after the break, [uXe] now as all the elements for playing Arduboy games on the GBA in place, including the ability to disable full screen scaling by using the shoulder buttons. Now he just needs to shrink the hardware down to the point it will fit inside of a standard GBA cartridge. Beyond that, who knows? Perhaps the appeal of being able to run Arduboy games on a real Game Boy is enough to warrant turning this hack into a new commercial product.

Thanks to a hardware swap we’ve seen Arduboy games played on the Dreamcast VMU, and [uXe] himself previously grafted Arduboy-compatible hardware into an original Game Boy, but being able to play these games on an unmodified Game Boy Advance obviously has its own appeal. At the very least, it will be a bit more ergonomic than using a hacked classroom gadget.

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Building A Semiautomatic Swag Launcher

February 15, 2019 by Tom Nardi 4 Comments

Regular readers of Hackaday have certainly seen the work of [Jeremy Cook] at this point. Whether you remember him from his time as a writer for this fine online publication, or recognize the name from one of his impressive builds over the last few years, he’s a bona fide celebrity around these parts. In fact, he’s so mobbed with fans at events that he’s been forced to employ a robotic companion to handle distributing his personalized buttons for his own safety.

Alright, that might be something of a stretch. But [Jeremy] figured it couldn’t hurt to have an interesting piece of hardware handing out his swag at the recent Palm Bay Mini Maker Faire. Anyone can just put some stickers and buttons in a bowl on a table, but that’s hardly the hacker way. In the video after the break, he walks viewers through the design and construction of this fun gadget, which takes a couple unexpected turns and has contains more than a few useful tips which are worth the cost of admission alone.

Outwardly the 3D printed design is simple enough, and reminds us of those track kits for Matchbox cars. As you might expect, getting the buttons to slide down a printed track was easy enough. Especially when [Jeremy] filed the inside smooth to really get them moving. But the goal was to have a single button get dispensed each time the device was triggered, but that ended up being easier said than done.

The first attempt used magnets actuated by two servos, one to drop the button and the other to hold up the ones queued above it. This worked fine…at first. But [Jeremy] eventually found that as he stacked more buttons up in the track, the magnets weren’t strong enough to hold them back and they started “leaking”. This is an excellent example of how a system can work perfectly during initial testing, but break down once it hits the real world.

In this case, the solution ended up being relatively simple. [Jeremy] kept the two servos controlled by an Arduino and a capacitive sensor, but replaced the magnets with physical levers. The principle is the same, but now the system is strong enough to hold back the combined weight of the buttons in the chute. It did require him to cut into the track after it had already been assembled, but we can’t blame him for not wanting to start over.

Just like the arcade inspired candy dispenser, coming up with a unique way of handing out objects to passerby is an excellent way to turn the ordinary into a memorable event. Maybe for the next iteration he can make it so getting a button requires you to pass a hacker trivia test. Really make them work for it.

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Text Projector With — You Know — Lasers

February 14, 2019 by Al Williams 9 Comments

We missed [iliasam’s] laser text projector when it first appeared, perhaps because the original article was in Russian. However, he recently reposted in English and it really caught our eye. You can see a short video of it in operation, below.

The projector uses raster scanning where the beam goes over each spot in a grid pattern. The design uses one laser from a cheap laser pointer and a salvaged mirror module from an old laser printer. The laser pointer diode turned out to be a bit weak, so a DVD laser was eventually put into service. A DVD motor also provides the vertical scan which is just a slight wobble of a mirror. A Blue Pill CPU provides all the smarts. You can find the code on GitHub.

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This Light-Up Sorter Is A Bright Idea

February 12, 2019 by Kristina Panos 14 Comments

Sorting out a mountain of screws and other workbench detritus by hand is a task that only appeals to a select few of us. [AdrienR] is not one of those people. He believes the job is better suited to a robot, so he built an intelligent and good-looking machine that does just that.

[Adrien]’s sorting bot is capable of organizing a hodgepodge of parts quickly and effectively. He simply scatters the parts on the light box work surface, illuminates it, and takes a picture with a downward-facing web cam. An algorithm studies the parts and their positions using OpenCV image processing, and sends the triangulation back to the arm so it can pick and place the parts into laser cut boxes using a home brew electromagnet.

[Adrien] calls this a work in progress. He plans to control it with a Raspberry Pi so it can be a standalone unit, and will probably move the parts boxes to the outside curve. Drop yourself past the break to see it sort.

If delta robots are more your sort, this one has balls. Colored balls.

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Play Chess Like Harry Potter

February 9, 2019 by Al Williams 10 Comments

If you are a Harry Potter fan, you might remember that one of the movies showed an Isle of Lewis chess set whose pieces moved in response to a player’s voice commands. This feat has been oft replicated by hackers and [amoyag00] has a version that brings together a Raspberry Pi, Arduino, Android, and the Stockfish chess engine in case you want to play by yourself. You can see a video of the game, below.

Interestingly, the system uses Marlin — the 3D printing software — to handle motion using the Arduino. We suppose moving chess pieces over a path isn’t much different than moving a print head. It is certainly a novel use of GCode.

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