Charliplexed 7-Segment Display Takes Advantage of PCB Manufacturers

Cutting out precise shapes requires a steady hand, a laser cutter, or a CNC mill, right? Nope! All you need is PCB design software and a fabrication facility that’ll do the milling for you. That’s the secret sauce in [bobricius]’s very pleasing seven-segment display design.

His Hackaday.io entry doesn’t have much detail beyond the pictures and the board files, but we’re not sure we need that many either. The lowest board in the three-board stack has Charlieplexed LEDs broken out to six control pins. Next up is a custom-routed spacer board — custom routed by the PCB house, that is. And the top board in the stack is another PCB, this one left clear of copper where the light shines out.

We want to see this thing lit up! We’ve played around with using PCB epoxy material as a LED diffuser before ourselves, and it can look really good. The spacers should help even out the illumination within segments, while preventing bleed across them. Next step? A matrix of WS2812s with custom-routed spacers and diffusers. How awesome would that be?

RGB LEDs: How to Master Gamma and Hue for Perfect Brightness

You would think that there’s nothing to know about RGB LEDs: just buy a (strip of) WS2812s with integrated 24-bit RGB drivers and start shuffling in your data. If you just want to make some shinies, and you don’t care about any sort of accurate color reproduction or consistent brightness, you’re all set.

But if you want to display video, encode data in colors, or just make some pretty art, you might want to think a little bit harder about those RGB values that you’re pushing down the wires. Any LED responds (almost) linearly to pulse-width modulation (PWM), putting out twice as much light when it’s on for twice as long, but the human eye is dramatically nonlinear. You might already know this from the one-LED case, but are you doing it right when you combine red, green, and blue?

It turns out that even getting a color-fade “right” is very tricky. Surprisingly, there’s been new science done on color perception in the last twenty years, even though both eyes and colors have been around approximately forever. In this shorty, I’ll work through just enough to get things 95% right: making yellows, magentas, and cyans about as bright as reds, greens, and blues. In the end, I’ll provide pointers to getting the last 5% right if you really want to geek out. If you’re ready to take your RGB blinkies to the next level, read on!

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magicShifter 3000: An Over-Engineered POV Stick with a 15-Year Journey

3 hackers, 16 LEDs, 15 years of development, one goal: A persistence of vision display stick that fits into your pocket. That’s the magicShifter 3000. When waved, the little, 10 cm (4 inches) long handheld device draws stable images in midair using the persistence of vision effect. Now, the project has reached another milestone: production.

The design has evolved since it started with a green LED bargraph around 2002. The current version features 16 APA102 (aka DotStar) RGB LEDs, an ESP-12E WiFi module, an NXP accelerometer/magnetometer, the mandatory Silabs USB interface, as well as a LiPo battery and charger with an impressive portion of power management. An Arduino-friendly firmware implements image stabilization as well as a React-based web interface for uploading and drawing images.

After experimenting with Seeedstudio for their previous prototypes, the team manufactured 500 units in Bulgaria. Their project took them on a roundtrip through hardware manufacturing. From ironing out minuscule flaws for a rock-solid design, over building test rigs and writing test procedures, to yield management. All magicShifter enclosures are — traditionally — 3D printed, so [Overflo] and [Martin] are working in shifts to start the 500 prints, which take about 50 minutes each to complete. The printers are still buzzing, but assembled units can be obtained in their shop.

Over all the years, the magicShifter has earned fame and funding as the over-engineered open hardware pocket POV stick. If you’re living in Europe, chances are that you either already saw one of the numerous prototype units or ran into [Phillip Tiefenbacher] aka [wizard23] on a random hacker event to be given a brief demo of the magicShifter. The project always documented the status quo of hardware hacking: Every year, it got a bit smaller, better, and reflected what parts happened to be en vogue.

magicshifter-timeline

The firmware and 3D-printable enclosure are still open source and the schematics for the latest design can be found on GitHub. Although, you will search in vain for layout or Gerber files. The risk of manufacturing large batches and then being put out of business by cheap clones put its mark on the project, letting the magicShifter reflect the current, globalized status of hardware hacking once more. Nevertheless, we’re glad the bedrock of POV projects still persists. Check out the catchy explanatory video below.

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Cyclist’s LED Pixel Clock Has No Fat Around The Middle

If you like LED clocks and illuminated bicycle wheels, [Harald Coeleveld] has just the right weekend project for you. His RGB pixel LED clock is as simple as it is beautiful, and it can be built in no time: The minimalist and sporty design consist of not much more than a LED strip wrapped around a bicycle wheel rim.

[Harald] took 2 meters of addressable WS2812 LED strip (with 30 LEDs per meter, we assume), wrapped it around a 27″ bicycle rim padded with a foam strip, and obtained 60 equally spaced RGB LEDs on a ring, ideal for displaying time. Apparently, the rim-tape circumference of this particular 27″ bicycle wheel is close enough to 2 meters, so it lines up perfectly.

On the electronics side, the project employs an Arduino Nano and a DS3231 precision RTC module. For switching between two illumination modes for day and night, [Harald] also added a photoresistor. During the day, colored dots around the ring display the time: A red dot for the seconds, a blue one for the minutes, and a group of 3 green LEDs for the hours. At night, the entire ring shimmers with an effective red glow for easier readability.

The Arduino code for this build can be downloaded from the project page, enabling anyone to effortlessly replicate this design-hack in under an hour!

TritiLED Lights Up The Night, Doesn’t Make You Glow

Tritium, or 3H is an isotope of hydrogen which has been used as everything from radiolabel in analytical chemistry to a booster to kickstart the chain reaction of nuclear weapons. Lately tritium’s most common use has been in key chains and jewelry. A small amount of tritium is stored in a phosphor coated glass tube. The beta decay of the tritium causes the phosphor to glow. The entire device is called a Gaseous Tritium Light Source (GTLS).

In the USA, GTLS devices are only allowed to be used in specific cases such as watches, compasses, and gun sights (MURICA!). Key chains and jewelry are considered frivolous uses and are prohibited by the nuclear regulatory commission. Of course, you can still order them from overseas websites.

The safety of GLTS devices have been hotly debated on the internet for years. They’re generally safe, unless you break the glass. That said, we’re happy getting our radiation exposure through cool hacks, rather than carrying a low-level source around in our pockets.

Enter [Ted Yapo], an amateur astronomer. After tripping over his telescope tripod one time too many, he decided to take matters into his own hands. He’s designing TritiLED, a dim LED light source which can last for years. [Ted] is using a  Luxeon Z LED, driven with PWM by a PIC 12F508 8 bit microcontroller. Running at 26.3 μA, he estimates about a year of run time on a CR2032 watch battery, or a whopping 15 years on a pair of lithium AA cells. Sure he could have done it with a 555 timer, but using a micro means more features are just a few lines of code away. [Ted] took advantage of this by adding a high brightness mode, blink modes, and an exponential decay mode, which emulates the decay of GLTSs.

Best of all it’s all open source. [Ted] is publishing under the (CC-BY-SA) license on Hackaday.io.

Incredible Luminosity in a Portable Package

If you’ve ever wanted to bring the brightest day into the blackest night, this flashlight shall give you sight. With a 100W LED array powered by up to 32V, this thing is exceedingly bright — it clocks in at about 9000 lumens! But the best part is that all every little detail of the build was documented along the way so that we can tag along for the ride.

The all-aluminium case houses the LEDs and their heat sink, voltage regulator and display, the AD and DC adapter and converter boards and their connectors, and fans to ensure adequate ventilation. It’s powered by a custom-assembled 6400 mAh 11.1V lipo battery or DC 20V 10Amp power supply via XLR for rugged, locking connection. The battery pack connection was vacuum formed for quick-swapping, and the pack itself will sound off an alert if any of the three batteries inside the pack run out of power. A nifty added feature is the ability to check the remaining charge — especially useful if you’re looking to bring this uncommonly powerful flashlight along on camping trips or other excursions.

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Making A Networked 32X32 LED Panel Case

[Adam Haile] of [Maniacal Labs] is at it again, whipping up some LED weirdness. This project is smaller than most of his work, though: he has made a nice case that holds a 32X32 LED matrix screen, the controller, and a Raspberry Pi. Check out the build and a brief demo in the video below.

This nice 3D printable design, called the Jumbo1K, would be a good starting point if you are looking to make something with one of these screens, as it provides easy access to all of the ports on the Pi for programming, debugging and networking the device without ruining the look. It does this with a neat trick, using the keystone jacks that you put in your wall when you are rewiring your house.
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