Polar Coordinate Mapping And RGB LED Disks

Last week, Adafruit released the DotStar RGB LED Disk, a 240mm diameter disk packed with 255 individually addressable RGB LEDs. Because blinkey glowey projects are the best projects, [Adam] had to have one. His tests open up some interesting possibilities in the world of blinkey LED stuff, including a polar coordinate display that would be perfect for low-res games and LED clocks.

[Adam] found the Disk sufficiently bright and glowey, but there were two problems. The first was the JST SM connector on the input of the DotStar Disk; with 255 LEDs on the disk, it has a maximum draw of over 10A, while the connector can only supply 7A without getting unreasonably warm. Secondly, there aren’t 60 LEDs around the outer edge of the disk, limiting its application as a clock.

There’s another thing wrong with the DotStar Disk, until you realize it’s effectively a polar coordinate display. RGB LED libraries are usually written for strips or matrices, not circles. The LEDs are sequentially arranged on the DotStar disk spiraling inwards, and after mucking about with some terrible code, [Adam] realized he could control a pixel with only its distance from center and angle from the connector. This makes plotting circles easier, but it also opens this display up to some interesting applications; circular Pong would be cool, and LED clocks are the bees knees.

An Introduction To Individually Addressable LED Matrices

The most fascinating project you can build is something with a bunch of blinky hypnotic LEDs, and the easiest way to build this is with a bunch of individually addressable RGB LEDs. [Ole] has a great introduction to driving RGB LED matrices using only five data pins on a microcontroller.

The one thing that is most often forgotten in a project involving gigantic matrices of RGB LEDs is how to mount them. The enclosure for these LEDs should probably be light and non-conductive. If you’re really clever, each individual LED should be in a light-proof box with a translucent cover on it. [Ole] isn’t doing that here; this matrix is just a bit of wood with some WS2812s glued down to it.

To drive the LEDs, [Ole] is using an Arduino. Even though the WS2812s are individually addressable and only one data pin is needed, [Ole] is using five individual data lines for this matrix. It works okay, and the entire setup can be changed at some point in the future. It’s still a great introduction to individually addressable LED matrices.

If you’d like to see what can be done with a whole bunch of individually addressable LEDs, here’s the FLED that will probably be at our LA meetup in two weeks. There are some crazy engineering challenges and several pounds of solder in the FLED. For the writeup on that, here you go.

[Mike] Illuminates us on LED Filaments

LED filaments started showing up in light bulbs a few months back. [Mike] discovered that the strips are available in bulk from ebay and Alibaba. Always keen to work with new LED technologies, [Mike] ordered a few for experimenting and posted the results on his [mikeselectricstuff] YouTube channel. He also added the information to his website.

The filaments consist of 28 LEDs connected in series. The blue LEDs are covered by the typical yellow phosphors to make them glow white. It’s interesting to note that some of the filaments use a removable silicone sleeve to hold the phosphor coating, while others are coated with a resin material. The LEDs themselves are bare dies mounted to a metal strip and joined by bond wires. The entire strip can be bent, but be careful, or you’ll break the fragile bond wires.

The strips do require a fair bit of voltage to operate. The entire strip runs best at around 75 and 10~15 mA, while putting out about 1 Watt of light. [Mike] tested a strip to destruction by pumping 40 mA through it. Predictably the strip went out when the bond wires melted. The surprising part was that the strip blinked back on as the wires cooled and re-connected. The strip and wires were working as a temperature controlled switch, similar to the bimetalic strip found in old fashioned “twinkling” incandescent Christmas lights.

Not satisfied with simple tests, [Mike] went on to build a clock using the filaments as elements of a seven segment display. Inspired by numitron and minitron displays, [Mike] built a single sided PCB which held the clock circuit on the bottom and the LED filaments on top. The filaments are spaced off the board by tall wire wrap sockets, which proved to be difficult to keep from shorting out. Texas Instruments TPIC6B595 chips were used to control the LED filaments. Logically the chip functions the same as a 75LS595, which means it can be driven with a SPI bus. The open drain outputs can handle 50 volts – which makes them perfect for this application.  The clock is tremendously bright, but there is still a bit of room for improvement. [Mike] notes that the phosphor of un-powered filaments tend to glow a bit due to light absorbed from nearby illuminated filaments. He’s experimenting with color filters to reduce this effect. At full power though, [Mike] says this clock would easily be daylight readable, and we don’t doubt it!

[Mike’s] final test was a bit whimsical – he built a cube entirely from the LED filaments. The cube looks awesome, but we can’t wait to see who will move things into the 4th dimension and build a tesseract!

Continue reading “[Mike] Illuminates us on LED Filaments”

Hacklet 43 – Flashlight projects

Mankind has always looked for ways to light up the night as they walk around. Fires are great for this, but they aren’t very safe or portable. Even kept safe in a lantern, an open flame is still dangerous – especially around cows.  Enter the flashlight, or torch if you’re from the other side of the pond. Since its invention in 1899, the flashlight has become a vital tool in modern society. From patrolling the dark corners of the city, to reading a book under the covers, flashlights enable us to beat back the night. The last decade or so has seen the everyday flashlight change from incandescent bulbs to LEDs as a light source. Hackers and makers were some of the first people to try out LED flashlights, and they’re still tinkering and improving them today. This weeks Hacklet focuses on some of the best flashlight projects on Hackaday.io!

light1We start with [Norman], and the LED Flashlight V2. Norman built a flashlight around a 100 Watt LED. These LEDs used to be quite expensive, but thanks to mass production, they’ve gotten down to around $6 USD or so. Norman mounted his LED a custom aluminum case. At this power level, even LEDs get hot. An extruded aluminum heatsink and fan keeps things cool. Power is from a 6 cell LiPo battery, which powers the LED through a boost converter. It goes without saying that this flashing is incredibly bright. Even if the low-cost LEDs aren’t quite 100 Watts, they still put many automotive headlights to shame! Nice work, [Norman].

light2A tip of the fedora to [Terrence Kayne] and his Grain-Of-Light LED LIGHT. [Terrence] loves LED flashlights, be he wanted one that had a bit of old school elegance. Anyone familiar with LEDs knows CREE is one of the biggest names in the industry. [Terrence] used a CREE XM-L2 emitter for his flashlight. He coupled the LED to a reflector package from Carlco Optics. The power source is an 18650 Lithium cell, which powers a multi-mode LED driver. [Terrence] spent much of his time turning down the wooden shell and aluminum tube frame of the flashlight. His workmanship shows! Our only suggestion would be to go with a lower profile switch. The toggle [Terrence] used would have us constantly checking our pockets to make sure the flashlight hadn’t accidentally been activated.

light3Harbor Freight’s flashlights are a lot like their multimeters: They generally work, but you wouldn’t want to trust your life to them. That wasn’t a problem for [Steel_9] since he needed a strobe/party light. [Steel_9] hacked a $5 “27 LED” light into a stylish strobe light. He started by cutting the power traces running to the LED array. He then added in an adjustable oscillator circuit: two BJTs and a handful of discrete components make up an astable multivibrator. A third transistor switches the LEDs. Switching a load like this with a 2N3906 probably isn’t the most efficient way to do things, but it works, and the magic smoke is still safely inside the semiconductors.  [Steel_9] built the circuit dead bug style, and was able to fit everything inside the original plastic case.  Rave on, [Steel_9]!

If you want to see more flashlight projects, check out our new list on Hackaday.io! That’s about all the time we have for this week’s Hacklet. As always, see you next week. Same hack time, same hack channel, bringing you the best of Hackaday.io!

1768 LEDs, Because 96 Just Wasn’t Enough

Some people would look at a massive 6’x4′ LED matrix hanging on the wall playing animations and be happy with the outcome. But [Ben] just isn’t one of those people. The original FLED (Fantastic LED thingy) was eight rows of twelve addressable LEDs for a total of 96 pixels. This spring he upped his game and retrofitted the display with 1768 LEDs.

It wasn’t simply an issue of restlessness, the original build suffered from LEDs dying. We actually featured it for that reason as a Fail of the Week.  This is not strictly a hobby project, it’s hanging on the wall in the Supplyframe offices, so pulling it down frequently to fix broken parts is not ideal.

fled-reborn-LED-layoutTo make FLED more reliable [Ben] sourced strips of the new APA102 LEDs which we looked at back in December. They use an SPI bus instead of the bizarre timing scheme of the WS2812. At first glance you’d think this would mean easier assembly compared to soldering both sides of each of the original 96-pixels. These do come in strips, but laying out 52×34 still means soldering to the ends of each row.

A lot of love went into making sure those rows were laid out perfectly. A sheet of white foamed PVC serves as the substrate. There is grounding braid on either end of the rows, one is the voltage bus, the other is ground. It fits the original enclosure which is acrylic and does a great job of diffusing the light. I’ve seen it in person and it looks pretty much perfect!

It’s not just the physical layout of this many pixels that is a challenge. Pushing the data to all of them is much harder than it was with 96. [Ben] transitioned away from RaspberryPi. He considered using a Teensy 3.1 and ESP8266 but the WiFi of these cheap modules is far too slow to push frame information from a remote box. In the end it’s a BeagleBone Black that drives the reborn display. This is a great choice since there’s plenty of power under the hood and a traditional (and much faster) WiFi dongle can be used.

Don’t miss the animation demos found after the break.

Continue reading “1768 LEDs, Because 96 Just Wasn’t Enough”

The Possibility Of Driving 16,000 RGB LEDs

Like just about everyone we know, [Luis] decided a gigantic RGB LED matrix would be a cool thing to build. Gigantic LED matrices are very hard to build, though: not only do you have to deal with large power requirements and the inevitable problems of overheating, you also need to drive a boat load of LEDs. This is not easy.

[Luis] found a solution to the problem of driving these LEDs with a new, fancy ARM Cortex M4 microcontroller. All Cortex M4 ARMs have DMA, making automatic memory transfers to peripherals and LED strips a breeze.

The microcontroler [Luis] is using only supports 1024 transfers per transfer set, equating to a maximum of 14 LEDs per transfer. This problem can be fixed by using the ping-pong mode in the DMA controller by switching between data structures for every DMA request. Basically, he’s extending the number of LEDs is just switching between two regions of memory and setting up the DMA transfer.

The result is much better than [Luis]’ original circuit that was just a bunch of SPI lines. It also looks really good, judging by the video below. It’s not quite a gigantic LED matrix yet, but if you want to see what that would look like, check out the huge 6 by 4 foot matrix hanging in the Hackaday overlord office.

Continue reading “The Possibility Of Driving 16,000 RGB LEDs”

Documenting Poorly Documented LED Strips

While [Drew] was in China for the Dangerous Prototypes Hacker Camp, he picked up some very bright, very shiny, and very cheap LED strips. They’re 5 meter “5050” 12V strips with 20 LEDs per meter for about $15 a spool. A good deal, you might think until you look at the datasheet for the controller. If you want an example of how not to document something, this is it.

A normal person would balk at the documentation, whereas [Drew] decided to play around with these strips. He figured out how to control them, and his efforts will surely help hundreds in search of bright, shiny, glowy things.

You are expected to tell the difference between 'GMODE', 'OMODE' and 'CMODE' in this pinout.
You are expected to tell the difference between ‘GMODE’, ‘OMODE’ and ‘CMODE’ in this pinout.

The datasheet for the LPD6803 controller in this strip – available from Adafruit here – is hilarious. The chip takes in clocked data in the order of Green, Red, and Blue. If anyone can explain why it’s not RGB, please do so. Choice phrasing includes, “VOUT is saturation voltage of the output polar to the grand” and “it is important to which later chip built-in PLL regernate circuit can work in gear.” Apparently the word ‘color’ means ‘gray’ in whatever dialect this datasheet was translated into.

Despite this Hackaday-quality grammar, [Drew] somehow figured out how to control this LED strip. He ended up driving it with an LPC1768 Mbed microcontroller and made a demo program with a few simple animations. You can see a video of that below.

Continue reading “Documenting Poorly Documented LED Strips”