# Giant LED Matrix Fills Blank Space In The Kitchen

We’ve all got one: a blank space somewhere in our home that we don’t know what to do with. [James Miller] had one above his kitchen cabinets, so he filled it with a giant LED matrix. The result is a large but surprisingly attractive LED screen that can send messages, provide illumination, or while away the idle hours of the night playing Conway’s Game of Life.

[James] built the matrix using the usual suspect for these builds: several strings of WS2812 lights . He initially ran this from a Raspberry Pi, but realized that there was no need for such a dizzying amount of computing power, so he switched to an ESP32 instead. The frame is built from wood and foam board.

The first version he built used a fabric diffuser, but after a close encounter with a flaming steak, he switched over to commercial ceiling light diffusers cut down to size. We might have been tempted to keep going and try an “egg crate” style ceiling light panel for a the smaller pixel size, but [James] thinks he has reached the “good enough” point of this project. It’s certainly a fun build, and it looks very cool with minimal materials.

# Math You Can Wear: Fibonacci Spiral LED Badge

Fibonacci numbers are seen in the natural structures of various plants, such as the florets in sunflower heads, areoles on cacti stems, and scales in pine cones. [HackerBox] has developed a Fibonacci Spiral LED Badge to bring this natural phenomenon to your electronics.

To position each of the 64 addressable LEDs within the PCB layout, [HackerBox] computed the polar (r,θ) coordinates in a spreadsheet according to the Vogel model and then converted them to rectangular (x,y) coordinates. A little more math translates the points “off origin” into the center of the PCB space and scale them out to keep the first two 5 mm LEDs from overlapping. Finally, the LED coordinates were pasted into the KiCad PCB design file.

An RP2040 microcontroller controls the show, and a switch on the badge selects power between USB and three AA batteries and a DC/DC boost converter. The PCB also features two capacitive touch pads. [HackerBox] has published the KiCad files for the badge, and the CircuitPython firmware is shared with the project. If C/C++ is more your preference, the RP2040 MCU can also be programmed using the Arduino IDE.

For more details on beautiful RGB lights, we’ve previously presented Everything You Might Have Missed About Addressable LEDs, and for more details on why they can be so fun to wear, check out our Hackaday Badgelife Documentary.

(Editor’s note: HackerBox makes and sells kits, is run by Hackaday Contributor [Joseph Long] IRL.)

As an introduction to embedded electronics and programming in a straightforward environment, there isn’t much out there that can hold a torch to the Arduino Uno. Cheap (especially if you count the clones), easy to find, and quick to deploy, with countless support libraries, it’s a go-to for many a hack. This scribe simply can’t remember how many he’s bought, hacked, and deployed over the years. But can it be improved? [John Loeffler] thinks so, and his 2023 Hackaday Prize entry, the Uno Plus+ could be the one.

After clearing the top deck of extraneous components (by shoving them on the bottom) there was much more space to expand the header labeling, so there can be no accidental misplacement of those DuPont wires this thing will inevitably sprout randomly.

The board also has an additional Stemma/Qwiic connector and a Neopixel LED for indication duties. Also sitting on the PCB bottom are a ton of opamps, to drive the header indicators. Yes, this board has a full set of colour-coded LED bling indicators, showing the logical state of each and every pin on all headers, giving an easy way to check the desired activity is occurring. Plus it looks cool. Illuminated headers? YES!

Think the Uno too light on resources to perform any meaningful modern workloads? Think again!

# Converting A B&W Enlarger For Colour Analog Photo Printing

[Koraks tinkers] was gifted a gargantuan photographic enlarger, a Durst Laborator 138 s, which is a unit designed specifically for black and white usage only. This was not good enough for [Koraks] so down the rabbit hole of conversion to colour we go! The moral of the story is this: if you can’t find it, build it. The hacker mentality. After wasting time and effort trying to source a period colour head for the thing, [Koraks] did the decent thing and converted what was already in front of them.

Now, if you’re thinking this process is simply a matter of ripping out the tungsten bulb and sticking a high-power RGB array in there, then you’re going to be disappointed! You see, colour photography of the era — specifically the RA4 process in this case — requires careful colour calibration and is heavily biased towards the red end of the visible spectrum, due to the colour curve of those tungsten bulbs we touched upon earlier.

The first attempt at using an off-the-shelf COB array was a bust — it simply wasn’t bright enough once the light had passed through the diffuser plate, and the light path losses were too high to expose the RA4 paper sufficiently, especially at the red end of the spectrum. Quite simply this is due to the reduced energy of red photons (compared to blue) making the desired chemical reaction rate too low. The solution is more power.

Another issue that quickly raised itself was that 8-bits of PWM control of the RGB components was inadequate since the ratio of blue to red required was so skewed, that only a few effective bits of blue channel control were usable, and that was far too granular to get the necessary accuracy.

[Koraks’] approach was to custom build an LED array with twenty red 3W LEDs and eight each of the green and blue devices. 12-bits of PWM resolution was delivered via a PCA9685 PWM controller, that also handily controlled the cooling fans. The whole thing was hooked up to an Arduino Nano, with an MCP23016 expander board performing the duty of interfacing the rotary encoders and trigger footswitch. In fact, several iterations of the LED array have been constructed and this four-part blog series (Part1, Part2, Part3, Part4) lays out the whole story in all its gory detail for your entertainment. Enjoy!

COB LED arrays are pretty nifty, checkout turning them into 7-segment displays, just because. If all you want is raw power, we reckon that 100W “should be enough for anyone…”

Thanks [macsimski] for the tip!

Update: Corrected the article header from ‘exposer head’ to ‘enlarger’ for clarity at the request of the project author.

# Lighting Up Glue Stick Bicycle Tyres With RGB

Being visible to motorists is a constant concern for cyclists, but we doubt [The Q] will have this problem with his RGB LED illuminated tires made from glue sticks.

The project started with a set of 3D-printed tire molds that bolt to the standard wheels. A bot of melted glue sticks is poured into the mold, allowed to cool, and the mold sections are removed with the help of a heat gun after cooling. We doubt the weight and hardness make the tires particularly practical, but you can’t make normal tires glow from the inside.

The idea to illuminate the tires probably came after molding, because they had to be cut off to fit the LEDs. [The Q] built a simple hot wire jig with a piece of nichrome wire between two screws and used it to cut a few millimeters from the inside of the tire and fit a sleeved RGB LED strip in the wheel. Power come from a set of three 18650 batteries housed with a wireless controller in a 3D printed hub-mounted enclosure.

Like [The Q]’s hubless and partial wheel bicycles, it’s a definite head-turner, with function following form.

# Washington, DC Finally Gets Its Own PCB Metro Map

There was a time, not so long ago, when folks who wanted to make their own custom PCBs would have found themselves in the market for a bucket of acid and a second-hand laser printer. These days, all you have to do is click a few buttons in your EDA program of choice and send the files off for fabrication. It’s easy, cheap, and nobody ends up with chemical burns.

This has obviously had a transformative effect on the electronics hobby — when you can place traces on a PCB like an artist using a brush, it’s only a matter of time before you get projects like [Logan Arkema]’s DCTransistor. This open source board uses carefully arranged RGB LEDs to recreate the Washington Metropolitan Area Transit Authority (WMATA) metro map, and thanks to an ESP8266 connected to their API, can display the positions of trains in real-time.

If you’re getting a sense of déjà vu here, it’s not just in your head. We’ve seen similar maps created for other major metropolitan areas, and [Logan] certainly isn’t trying to take credit for the idea. In fact, he was a bit surprised to find that nobody had ever made one for the DC area — so he decided to take on the challenge himself. He reasoned it would be a good way to hone his PCB design skills and become more comfortable with embedded development. We’d say the end result proves his theory correct, and makes one more city that can boast about its IoT cartography.

Looking to hang a DCTransistor on your own wall? [Logan] says he’ll be dropping the board design files and schematics into the project’s GitHub repository soon, and he also plans on selling pre-made boards in the near future.

We covered this London “tube” map back in 2020, and were impressed by the attention to detail that went into similar displays for Tokyo, Singapore, and the San Francisco Bay Area a year later. Perhaps it’s time to map out your own hometown in LEDs?