Navigation Thing: Four Days, Three Problems, and Fake Piezos

The Navigation Thing was designed and built by [Jan Mrázek] as part of a night game activity for high school students during week-long seminar. A night-time path through a forest had stations with simple tasks, and the Navigation Thing used GPS, digital compass, a beeper, and a ring of RGB LEDs to provide a bit of “Wow factor” while guiding a group of students from one station to the next. The devices had a clear design direction:

“I wanted to build a device which a participant would find, insert batteries, and follow the beeping to find the next stop. Imagine the strong feeling of straying in the middle of the night in an unknown terrain far away from civilization trusting only a beeping thing you found. That was the feeling I wanted to achieve.”

The Navigation Things (there are six in total) guide users to fixed waypoints with GPS, a digital compass, and a ring of WS2812 LEDs — but the primary means of feedback to the user is a beeping that gets faster as you approach the destination. [Jan] had only four days to make all six units, which was doable. But as most of us know, delivering on a tight deadline is often less about doing the work you know about, and more about effectively handling the unexpected obstacles that inevitably pop up in the process.

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Keep Tabs on the Weather with rpi_status

[Facelessloser] is interested in glanceable information. Glancable devices are things like your car’s dashboard, your wristwatch, or widgets on a smartphone lockscreen. The glanceable information distribution system in this case is rpi_status, [facelessloser’s] entry in the Enlightened Raspberry Pi Contest.

[Facelessloser] coupled a ring of eight WS2812 RGB LEDs with a small OLED screen managed by a the common ssd1306 controller. Since he was rolling his own board for this project, [faceless] some buttons and a BMP180 temperature sensor. Going with popular parts like this meant libraries like the Pimoroni unicorn hat library for the WS2812 were readily available.

A simple display like this can show just about anything – from status of a nightly software build, to traffic along your morning commute. [Facelessloser] is using it for weather data. His data source is Weather Underground’s API. Weather information is displayed on the OLED. The WS2812’s display the temperature. A single blue light means cold. The ring fills as the temperature warms up. After eight degrees of blue, the color changes to orange, followed by red.

Check out the video after the break for a short demo of the board.

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Driving 16 WS2812B Strips with GPIOs and DMA

[Martin Hubáček] wrote in with his WS2812 LED library for the STM32F3 series processors. [Martin]’s library takes the same approach as [Paul Stoffregen]’s OctoWS2811 for the Teensy, and [Erich Styger]’s for the Freescale FRDM-K64F board. That is, it uses three DMA channels to get the signal out as fast as possible.

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Altitude Controlled LED Jacket Changes Color as You Climb

When your climbing gym throws a “glow in the dark” party, how can you stand out? For [Martijn], the answer was obvious. He made a jacket adorned with 32 WS2812 addressable LEDs whose color is addressable depending on the altitude to which he has climbed.
The build is centered on an Arduino Pro Mini with a barometric sensor and an NRF24L01 for radio comms. A pair of pockets contain AA batteries for power, and he’s all set to climb.
A base station Arduino with the same set-up transmits an up-to-the-minute reading for ground level temperature, which is compared to the local reading from the barometric sensor and used to calculate a new color for the LEDs. A Kalman filter deals with noise on the pressure reading to assure a stable result. Arduino sketches for both ends are provided on the page linked above.
The LEDs are mounted on the jacket’s stretch fabric with an excess of  wire behind the scenes to cater for the stretch. You can see the resulting garment in the short YouTube video below the break.

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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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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!

Orbs Light to Billie Jean on this Huge Sequencer

Sequencers allow you to compose a melody just by drawing the notes onto a 2D grid, virtually turning anyone with a moderate feel for pitch and rhythm into an electronic music producer. For  [Yuvi Gerstein’s] large-scale grid MIDI sequencer GRIDI makes music making even more accessible.

Instead of buttons, GRIDI uses balls to set the notes. Once they’re placed in one of the dents in the large board, they will play a note the next time the cursor bar passes by. 256 RGB LEDs in the 16 x 16 ball grid array illuminate the balls in a certain color depending on the instrument assigned to them: Drum sounds are blue, bass is orange and melodies are purple.

Underneath the 2.80 x 1.65 meters (9.2 x 4.5 foot) CNC machined, sanded and color coated surface of the GRIDI, an Arduino Uno controls all the WS2812 LEDs and reads back the switches that are used to detect the balls. A host computer running Max/MSP synthesizes the ensemble. The result is the impressive, interactive, musical art installation you’re about to see in the following video. What better tune to try out first than that of Billie Jean whose lighted sidewalk made such an impression on the original music video.

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