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Description: The SparkFun LED Array is a set of 56 red LEDs arranged in a nice 8x7 grid. This little board requires eight pins while the library supports any ATmega 168 and 328-based Arduino device. The SparkFun LED Array was developed to be used in conjunction with the BadgerStick as a fun and interactive way for people to learn about soldering and engage with SparkFun products at the multiple trade shows we appeared at. Now this LED array is available to everyone!

This board relies on the Charlieplexing technique to control individual LEDs, which means less GPIO pins are used (as opposed to a traditional grid format). Through the use of Charlieplexing we have been able to control all 56 LEDs with a total of only eight pins (labeled ‘A’ through ‘H’). With a little bit of code you will be able to cycle through all combinations of the pins to turn each LED on individually, and if cycled fast enough, you can create simple images and text!

Dimensions: 43.75mm Long x 28.5mm Wide

Documents:

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Customer Comments

  • 8x7? cringe Wai u no 8x8?

    Yes, I know it would take 9 pins to do 8x8, but I would sacrifice another pin for 8x8

    • I’d argue the 8-pin route is better.
      9-pins spans more than one port on AVR controllers. If it was 9 pins, I’d have to :

      DDRB |= 0xFFu;
      DDRC |= 0x01u;
      
      PORTB |= 0x55u;
      PORTC |= 0x01u;
      

      It is double the code your way.

      8-pins is much better and allows for more compact code.

      • Paired with the Redstick, though, it’d be awkward to get 8 I/O on a single port anyway. The only 8-bit I/O port that’s fully available is port D (as two pins of port B are used for the oscillator). But two pins of port D are used for the UART, and (on the Redstick, at least) are physically separated from the rest of port D.

        …But yeah, can you even imagine setting those I/O lines one at a time like Arduino encourages you to? :)

        • Arduino is great to get people into the hobby of embedded space, but in professional practice, it makes me cry

    • It’s Charlie-plexed and uses 8 I/O lines. 8x7 is the maximum size under those conditions.

      Basically, to light a LED you choose one I/O line to apply positive voltage to, and one to apply negative voltage to. When you select the line for positive voltage it can be any of the 8. But when you select the one for the negative voltage, it can’t be the same one you chose for the positive voltage, so you only have 7 choices. Thus, 8x7.

      • I know exactly how charlieplexing works. I’m saying I’d rather use 9 pins to do 8x8 than 8 pins to do 8x7

        • Well the way you phrased the question sounded like you didn’t. If your comment about using a ninth pin was in there when I replied, I guess I missed it. Sorry, didn’t mean to explain something you already understood.

          Don’t know specifically what went into their design decisions there. I suppose they were trying to strike some balance between capability and economy, given that this was originally a give-away item.

          • No, it was definitely unclear when I posted it. I edited shortly after, and you probably read it in between the original post and the clarified post. No worries.

      • FWIW, just a couple of days ago the folks over at Adafruit have introduced some 9x16 chalieplexed arrays in several different colors. Also a breakout board for an I2C charlieplex driver chip.

        • In case that one doesn’t work for somebody, check out the AS1130 from austria microsystems. Same amount of LEDs as the linked one, just another option

  • rherman / last year / 1

    Overall, this looks like a great product. Making such a large array in a small package with just eight IOs is a fantastic idea. However, the lack of contrast between the red light of the LEDs and the bright red silkscreen appears to be a drawback.

    To my eyes, when looking at both the pictures provided and the showcase video, it’s difficult to discern the lit from the unlit LEDs. In the video, even when the ambient light is turned down somewhat, the array is still not quite distinctive enough. I can understand the reasons: red LEDs are typically cheaper, power consumption versus brightness is an issue and, being a Sparkfun product, it’s natural to make the silkscreen red for both branding and cost. If it is going to be operated in at least near darkness or some kind of contrasting cover to shine through is used, then I suppose my concerns are probably irrelevant. Otherwise, I think changing the colour of either the silkscreen or the LEDs should be considered to make it a more useful product.

    • Thanks for the feedback! We’ll definitely consider multiple colors for possible revisions.

  • Are there any plans to make this with rgb or white LEDs?

    • Not at this time. RGB in this form factor would be hard, as you would need 24 pins to keep Charlieplexing. If there is enough interest for other colors, we might make them :)

  • SparkFun … you can go DENSER:

    http://i.imgur.com/J53FeSN.jpg

    That’s an 8x8 array of 0603 LEDs with an outer dimension of 2/3 inch

    Also, on a side note, I had to reset my password for my account to comment (which required me to respond to an e-mail link) and then I had to verify my e-mail … which was funny.

    • I played with a denser layout, but ultimately decided to space them out more to make the 8x7 look bigger, which worked well as an event giveaway.

  • Product Suggestion: Redo layout so input pins (a-h) are on top or bottom with additional space for mounting holes and eliminate the extra board space where existing mounting holes and logo are now.. Reason: Would allow for left to right stacking of these to create a scrolling LED display 8Xn number of boards. Would need GPIO expander(s) and LED driver(s) but would offer next step in experimentation.

    • +1 for fixing the spacing so you can tile the boards left to right. You’re sooo close….

  • Yes finally you guys offer charlieplexed led boards! This should have been done a long time ago but I’m so glad its finally here

  • What are the dimensions of the board? And what color are the LEDs? (It looks like just red from the tutorial?) Are they RGB?

    • If you check the second image on the product we’ve put rulers up.

      The board is 4.375 cm long and 2.85 cm wide.

      Also, the LEDs are red. :)

    • they are not RGB. you could theoretically do RGB with charliplexing, but it would require using almost all the IOs of an Uno.

      I would expect red since that’s what the schematic and tutorial say, but I guess that could change in the future.

  • The GitHub link Design Files & Example Code is not correct (404)

Customer Reviews

4.7 out of 5

Based on 3 ratings:

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Great display!

These are awesome displays, perfectly sized for fitting to glasses for that secret-agent look. It’d be nice if there were more tutorials on how to create images, slideshows, text, etc, but I expect those will come soon enough now that the display is for sale and not just a badgerhack giveaway. Reliable display, capable of some very cool stuff.

Easy to use and a lot of fun

This board is perfect for use with the Pro Mini boards because it lines right up with the I/O pins. It didn’t take any time at all to have it up and running and making cool patterns like rolling sine waves.

Related Tutorials

SparkFun LED Array (8x7) Hookup Guide

March 10, 2016

Getting started with the Charlieplexed 8x7 LED array.