Documenting Poorly Documented LED Strips

April 12, 2015 by Brian Benchoff 24 Comments

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.

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Overengineering Beer Pong

April 11, 2015 by Brian Benchoff 15 Comments

If there’s one game that deserves to be overengineered with hundreds of LEDs, sensors, and electronic modules, it’s beer pong. [Jeff] has created the most ostentatious beer pong table we’ve ever seen. It’s just shy of playing beer pong on a single gigantic LED display, and boy, does it look good.

The table includes a 32×12 grid of LEDs in the center of the table, with 10 pods for Solo cups at each end of the table. These pods have 20 RGB LEDs each and infrared sensors that react to a cup being placed on them. The outer edge of the table has 12 LED rings for spectators, giving this beer pong table 1122 total LEDs on 608 individual channels.

With that many LEDs, how to drive all of them becomes very important. There’s a very large custom board in this table with a PIC24 microcontroller, TLC5955 PWM drivers, and enough IDC headers to seriously reconsider using IDC headers.

Put enough LEDs on something and it’s bound to be cool, but [Jeff] is taking this several steps further with some interesting features. There’s a Bluetooth module for controlling the table with a phone, a VU meter to give the table some audio-based visualizations, and air baths for cleaning the balls; drop a ball down the ‘in’ hole, and it pops out the ‘out’ hole, good as new. If you’ve ever wondered how much effort can go into building a beer pong table, there you go. Video below.

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DIY Seven Segment Displays

April 4, 2015 by Brian Benchoff 9 Comments

[Esai] wanted to build an electronic clock from scratch. A noble quest, but ordinary seven-segment displays are just that – incredibly ordinary. Instead of a few displays that can be bought from the usual retailers for a dollar a piece, [Esai] made his own four digit, seven-segment display on some perfboard.

Before soldering 58 SMD LEDs to a small rectangle of perfboard, [Esai] traced out each segment with a marker. Two LEDs make up each segment, and they’re all connected to a breadboard-friendly pin header with 30 gauge wire.

Each segment is connected as a single column in the LED matrix, and each digit is a row. It’s a simple design, but there aren’t any resistors on this board. Hopefully [Esai] will be using a proper LED driver with this display; you really don’t want LEDs to burn out twice a day at 1:11.

3D Spectrum Analyzer Uses 1280 LEDs

March 23, 2015 by Ethan Zonca 47 Comments

One of [Dooievriend]’s friends recently pressed him into service to write software for a 3d spectrum analyzer/VU that he made. The VU is a fairly complex build: it’s made up of 1280 LEDs in a 16x16x5 matrix controlled by a PIC32 clocked at 80MHz. [Dooievriend] wrote some firmware for the PIC that uses a variation on a discrete Fourier transform to create a 3D VU effect.

When [Dooievriend] set out to design the audio analyzing portion of the firmware, his mind jumped to the discrete Fourier transform. This transform calculates the amplitude in a series of frequency bins in the audio—seemingly perfect for a VU. However, after some more research, [Dooievriend] decided to implement a constant Q transform. This transform is very similar to a Fourier transform, but it takes into account the logarithmic way that the human ear interprets sound.

[Dooievriend] started implementing the constant Q transform using an interrupt-based sampler, but he quickly ran into issues with slow floating-point math on his PIC32 (which doesn’t have a hardware floating-point unit). Thankfully he rewrote his code using fixed-point math, and the transform runs nearly real-time. Check out the video after the break to see the VU in action, and a second video that gives some details on the hardware build.

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Rebraining An LED Marquee With A SparkCore

March 20, 2015 by Mike Szczys 6 Comments

Wires? Where this LED scroller is going we don’t need wires. Well, except for power but everything needs power. The 90×7 LED marquee hangs over the entrance to NYC Resistor’s laser cutter room. Thanks to a Spark Core and a bit of work from [Trammell Hudson], the sign is working and attached to the network.

The original unit called for an RS485 connection for input. Other than that there wasn’t really a reason it had been collecting dust. Closer inspection of the internals proved that the display is driven exactly as you would expect: transistors for the rows and shift registers for the columns. Well, actually the columns are split into separate shift registers for the even and odd but that doesn’t complicate things too much. GPIO takes the seven row-driving transistors, two shift register clocks, data, latch, and enable for a total of twelve pins.

The Spark Core completely replaces the Atmel 80C32X2 and its RTC by pinging the network for UTC time synchronization once per day.

[via NYC Resistor]

An Experiment In Shift Registers And Multiplexed LEDs

March 18, 2015 by Brian Benchoff 15 Comments

[Kratz] is working on a WiFi controlled scoreboard, but before building the full-scale version, he thought it would be wise to test out the multiplexing technique for the display. The experiment worked, but unless this scoreboard is for a foosball table, he still has a lot of work ahead of him.

The design of this prototype display is pretty simple, with just two ‘595 shift registers feeding bits to the display. Sixteen NPN transistors are being used to sink and source current to the display. It’s a relatively simple circuit, allowing [Kratz] to fit nine seven-segment displays on a small board with only six wires – ground, two V+ for the logic and LEDs, clock, data, and latch – going to the microcontroller.

There were a few snags in the design; the data is clocked in on a rising edge, but an extra falling edge was required before latching. [Kratz] can’t figure out the reason for this, and it might just be a timing issue.

A Motor, An Arduino And A Whole Bunch Of Laser Cutting

March 16, 2015 by James Hobson 14 Comments

[Guido] was recently commissioned to build a kinetic sculpture for a client who wanted something unique. What he came up with is really awesome.

It’s called ORBIS: The Wooden Kinetic & Lighting Sculpture. It mounts to the wall and provides a focal point for the room – a bright flashy spinning one at that! Does it just stay there and do random things? Nope, of course not! [Guido] built it with a unique control box, two Arduino 2560’s and an Xbee to communicate between them.

He was told to design it using old and new technologies so he’s got a rotary phone dial on the side of the box which allows the user to change through the different modes.

Switches on top also let you change the color of the sculpture and the speed at which it moves around. Since it’s wireless it can be easily set on the coffee table and become an instant conversation starter.

See it in action after the break.

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