Addressable 7-Segment Displays May Make Multiplexing A Thing Of The Past

January 12, 2019 by Dan Maloney 52 Comments

[Sean Hodgins] has a knack for coming up with simple solutions that can make a big difference, but this is one of those “Why didn’t I think of that?” things: addressable seven-segment LED displays.

[Sean]’s design is basically a merging of everyone’s favorite Neopixel RGB LED driver with the ubiquitous seven-segment display. The WS2811 addressable RGB driver chip doesn’t necessarily have to drive three different color LEDs – it can drive three segments of the same display. With three of the chips on a single board, all seven segments plus the decimal point of a display can be controlled over a single data line. No more shift registers, no more multiplexing. And as a nice touch, individual displays can be ganged together with connectors on the back of each module. [Sean] has some code to support the display but is looking for someone to build a standalone library for it, so you might want to pitch in. Yes, he plans to sell the boards in his shop, but as with all his projects, this one is open source and everything you need to build your own is up on GitHub. The brief video below shows a few daisy-chained displays in action.

Like many of [Sean]’s designs, including this Arduino rapid design board, this is a simple way to get a tedious job done, and it wrings a lot of functionality from a single IO pin.

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LEDs And Pi Let You Virtually Decorate This Online Christmas Tree

December 23, 2018 by Dan Maloney 6 Comments

Anyone who has decorated a Christmas tree knows that the lights are what really make the look. But no matter how many strings you wrap around it, there never seems to be enough. Plus the standard sets either sit there and do nothing, or just blink on and off at regular intervals. Yawn.

But hackers aim higher, and [leo.currie]’s interactive “paintable” Christmas tree takes the lighting game a step beyond. The standard light strings are replaced with strings of WS2811 RGB LEDs which are wired to an ESP8266. A camera connected to a Raspberry Pi is setup up to stream images of the tree to all and sundry on the Interwebz, but with a special twist: it also creates a map of every light on the tree. That allows the lights to be controlled individually in response to user inputs on a web page hosted on the Pi. The upshot is that you can paint the tree with any color you like in real time, or upload various animated GIFs to display on the tree. You can play with the tree directly, or watch a replay on the video below when that Pi inevitably gets hugged to death.

Imagine the possibilities with this. Why not hang a lot of LED strings vertically from the eaves of your house and make a huge, low-resolution display? We’ve featured plenty of large, interactive LED Christmas displays before, and we’d love to see what you come up with.

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Engineer’s Primer On DIY Christmas Light Shows

January 9, 2017 by Lewin Day 26 Comments

Each year brings new Christmas light shows, with synchronised music and wild blinking decorations to light your eyeballs ablaze. Now, many of us have dabbled in the dark arts of blinken, tinkering with LEDs or flashing a neon bulb or two. There’s plenty of tutorials on how to control all manner of lights, but they’re often written for novices. Learning the basics of electronics for the nth time when you just need to know the specifics of a protocol or what IC you need can be a total drag. That’s why [Bill Porter] has written the Engineer’s Guide to DIY Computer Controlled Holiday Lights.

[Bill] covers the topic from start to finish – not just the technical side of things, but practical considerations about where to source components, and timescales for keeping your project on track. It’s no coincidence this is coming out in January – if you want to get something big up and running for Christmas, it’s time to start now! The guide gives links to forum communities that put in large group orders for parts early, and ship them slow to save money.

Other areas covered include software for creating advanced sequences for your lighting setup, which allow you to map animations over your entire layout. There’s also tips on which controller hardware to use for incandescent lights and the now-ubiquitous WS2811 strings. Even better, [Bill] shares specific tips on how to avoid common problems like voltage drop over long pixel runs and communication issues.

It’s a testament to [Bill] and his experience – the guide is an excellent way to get right up to speed with the state of the art in DIY Christmas light shows, and will save you from all manner of pitfalls. If you need to build something big this year and don’t want to reinvent the wheel, this is for you.

It’s not the first time we’ve heard from [Bill] either – check out his stunning wedding invitations or his repair of a science museum exhibit.

Driving 16 WS2812B Strips With GPIOs And DMA

October 6, 2016 by Elliot Williams 8 Comments

[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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Using WS2811 Chip To Drive Incandescent Lamps

June 12, 2016 by Elliot Williams 6 Comments

What makes the WS2812-style individually addressable pixel LEDs so inviting? Their rich colors? Nope, you can get RGB LEDs anywhere. Their form factor? Nope. Even surface-mount RGBs are plentiful and cheap. The answer: it’s the integrated controller. It’s just so handy to speak an SPI-like protocol to your LEDs — it separates the power supply from the data, and you can chain them to your heart’s desire. Combine this controller and the LEDs together in a single package and you’ve got a runaway product success.

But before the WS2812, there was the WS2811 — a standalone RGB controller IC. With the WS2812s on the market, nobody wants the lowly WS2811’s anymore. Nobody except [Michael Krumpus], that is. You see, he likes the old-school glow of incandescent, but likes the way the WS2812 strings are easy to drive and extend. So he bought a bag of WS2811s and put the two together.

The controller IC can’t handle the current that an incandescent bulb requires, so he added a MOSFET to do the heavy lifting. After linking a few of these units together, he discovered (as one does with the LED-based WS2812s eventually) that the switching transients can pull down the power lines, so there is a beefy capacitor accompanying each bulb.

He wanted each bulb to be independently addressable, so he only used the blue line of the RGB controller, which leaves two outputs empty. I’m sure you can figure out something to do with them.

Needless to say, we’ve seen a lot of WS2812 hacks here. It’s hard to pick a favorite. [Mike] of “mike’s electric stuff” fame built what may be the largest installation we’ve seen, and this hack that effectively projection-maps onto a randomly placed string of WS2812s is pretty cool. But honestly, no project that blinks or glows can go far wrong, right?

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Massive Flexible LED Strip Display Has Too Many Pixels?

March 25, 2016 by James Hobson 27 Comments

This massive LED display was assembled on a PVC banner (it can be rolled up!) measuring 2m by 1.5m, it boasts well over 6000 pixels, and as you can see from the photo — looks fantastic.

We recently published a post on How Many LEDs are Too Many, which spawned many comments showing off even more impressive displays with even higher LED counts. This is just one of them — and making it flexible as well? That’s just the icing on the cake.

To make the display flexible, [Elektric-Junkys] had a custom PVC banner printed with stripes to help them align 58 parallel strips of WS2811 LEDs on the surface.

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Driving WS2811 LEDs With…VGA?

January 4, 2016 by Elliot Williams 12 Comments

We thought we’d seen it all. All the ways to drive WS2811/2812 “Neopixel” LEDs, that is. And then [Steve Hardy] comes up with a new one: hacking a computer’s VGA output to drive 500 WS2811s in a string. And it’s quite a hack. You can check out the video (it’s worth enduring the horrible wind noise) below the break.

[Steve]’s big realization was that he could send the digital data that the Neopixels needed by carefully selecting a resolution and clock rate for the VGA to match the timings that the WS2811 modules wanted. A resolution of 840×1000 at 28MHz produces 70 pixels per WS2811 bit, or 12 bits per line. This means two VGA lines need to be sent for the RGB triple for each LED, hence the 1000 rows.

There are some further tricks before [Steve] got around to writing a custom OpenGL shader that converts regular graphics to his strange black-and-white bit pattern to drive the LEDs, but you’re going to have to read [Steve’s] blog for all that. If you’re waiting for a full code write-up, [Steve] says that one’s pending.

We’re just stoked to see the computing power that lies within a video card used for other purposes. Once you think of the VGA output as a general-purpose high speed (analog!) output, it opens up a whole bunch of possibilities if you can write the corresponding video software. As [Steve] points out, he’s only using the red channel right now — he could trivially add another 1000 LEDs just by tweaking his video code.

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