[Johan Beyers] built an elegantly simple Dog Speedometer project that uses a POV display to display a running dog’s speed without the benefit of an accelerometer. Using an Arduino (looks like it might be a D-love) and a line of 5 LEDs, [Johan] built a dirt-simple POV — 39 lines of code — that times out the flashes so that an immobile viewer sees the dog’s speed. How do you know your pup’s loping speed? That’s the beauty of this project.
Instead of putting all of the LEDs in a line, they are arranged in a V-shape. Because of this spatial offset, the patterns flashed out only “look right” at the right speed. Each number is flashed at a different speed, so you just look for the least distorted numeral.
[Johan]’s code does only what it needs to get the job done. The character data are stored in arrays that are played back directly to the pins of PORTD — avoiding most of the usual Arduino-style complexity with pin definitions and other foolery.
The first 10 seconds of the video below completely explains how [Evan] accomplished this build. A pair of custom cams wiggles the laser pointer through the correct sequences of coordinates to trace the desired pattern out when cranked by hand through a 1:5 ratio gear train. But what’s simple in concept is a bit more complicated to reduce to practice, as [Evan] amply demonstrates by walking us through the math he used to transfer display shapes to cam profiles. If you can’t follow the math, no worries — [Evan] has included all the profiles in his Thingiverse collection, and being a hand model software guy by nature, he’s thoughtfully developed a program to automate the creation of cam profiles for new shapes. It’s all pretty slick.
Looking for more laser POV goodness? Perhaps a nice game of laser Asteroids would suit you.
Death Stars were destroyed twice in the Star Wars movies and yet one still lives on in this 168 LED persistence of vision globe made by an MEng group at the University of Leeds in the UK. While Death Stars are in high demand, they mounted it on an axis tilted 23.4° (the same as the Earth) so that they can show the Earth overlaid with weather information, the ISS position, or a world clock.
More details are available on their system overview page but briefly: rotating inside and mounted on the axis is a Raspberry Pi sending either video or still images through its HDMI port to a custom made FPGA-based HDMI decoder board. That board then controls 14 LED driver boards mounted on a well-balanced aluminum ring. All that requires 75W which is passed through a four-phase commutator. Rotation speed is 300 RPM with a frame rate of 10 FPS and as you can see in the videos below, it works quite well.
Hackaday was in Portland last weekend for the Open Hardware Summit. I did a brief recap earlier this week but this post has been on my mind the entire time. The night before the summit, OSH Park (the Purveyors of Perfect Purple PCBs which we all know and love) hosted a Bring-A-Hack at their headquarters. [Laen] knows how to throw a party — with a catered spread and open bar which all enjoyed. The place was packed with awesome hackers, and everyone had something amazing to show off.
In fact, there were far too many people showing off hardware for me to capture all in one evening. But join me after the jump for six or seven examples that really stuck out.
As the story goes, years ago [Matt Evans] was wooing the beautiful and talented [Jen]. There were many suitors vying for her hand; he would have to set himself apart. The trouble was, how to convince her that persisting in the relationship was the best and only course? What did he have to offer? Of course many of us know the answer; having wooed our own significant others with the same thing. Incredible and unrepentant nerdiness.
So! He toiled late into the night, his eyes burning with love and from the fumes of solder smoke. For her he would put his wizardry to work. At the wave of a hand would write songs of adoration in the air with nothing but light. The runes of power, all typed out in the proper order, would be held by a ATiny. A CR2032 coin cell provided the magic pixies which would march to its commands, delivering their spark to the LEDs in the right order.
He etched the board, wrote the code, and soldered the components. He encased it in his finest box of crystal clear plastic and black static foam, a gift of the samples department of the Maxim corporation.
Presumably the full moon was high in the air when he presented the box. He took it out and waved it with a flair. Poetry floated there in front of her eyes. It read, “Jen is cool!”. A few years later, they were married.
You think you’ve seen everything that there is to see regarding blinking LEDs and then a simple little trick proves you wrong. Our friend [Zach Fredin], aka [Zakqwy], added a pander mode to his blinky board which shows the Hackaday Jolly Wrencher in a Persistence of Vision mode. We love pandering, and obviously you just need to start the mode and wave the board back and forth. But in thinking the obvious you’d be wrong.
You would think that soldering all those LEDs by hand would be the trick, but [Zach] pulled off a much more difficult feat. Look closely at the image here (or click to embiggen). The two shift register footprints on the prototype were mirrored. He deadbug soldered each of them using — get this — the individual strands from some 28 AWG stranded wire. You sir, get the hardcore hand soldering badge and then some.
Okay, we’ll stop beating around the bush. The ATtiny45 on this board isn’t connected to the USB data lines, they’re only for power. That means, at its heart this is purely a blinking LED project, albeit one that uses the huge range of colors of the PICOLED family of parts. [Zach] did well with just two user inputs, but it’s the very simple POV party trick that really sucked us in. Instead of waving the board around, [Zach] uses a metal offset spatula as a mirror. Moving it back and forth unfolds the carefully timed flashes to draw your message in the air. Such a simple concept, but so satisfying to see it applied in a slightly different way.
Persistence of vision projects were once all the rage, judging by a quick review of the literature here on Hackaday. They’ve tapered off a bit lately, but this impressive full-color globe display might just kick-start some new POV projects.
Built as a final project for an EE course, [Evan] and [Kyle]’s project is more about the control electronics and programming than the mechanical end of the build. Still, spinning a 12″ ring of 1/4″ thick acrylic with a strip of APA102 LEDs glued to the edge takes some thoughtful engineering. While the build appears sturdy, [Evan] does admit to a bit of wobble under full steam, which was addressed by adding some weight to the rig. We wonder if mounting half the LEDs on each side of the ring to balance the forces wouldn’t have worked better. True, it would have complicated the coding for the display, but maybe that would have been good for extra points. In any case, the display turned out well and the quality of the images is great. And as an aside: how awesome is it that we live at a time when you can order a six-circuit slip-ring for a project like this for less than $20?
It’s the end of the semester and we love seeing the final projects that have just made it across the finish line. This globe is one, yesterday we saw a voice-controlled digital eye exam, and if you have or know of a final project, don’t forget send us the link!