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Is there a way to control many (120ish) LEDs using a computer without having to control using a matrix array? Answered

I am trying to make a learning guitar that has an LED at every fret (so around 120 individual LED outputs), and after lots of research I am finding it difficult to find a way to control that many LEDs individually. I want to be able to turn on multiple LEDs at once for a chord so using a matrix array will cause unintentional LEDs to come on.

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steveastrouk (author)2009-08-01

Matrix operation does NOT mean you can't have "more than one" LED on at once, you can muliplex them, so, to the human eye there is more than one on at once, but electrically there is in fact only one row or column active at once.

One part I know of, for this, is probably the MAX 7221 or the MAX 7219. I've used hundreds over the years. One chip will run 64 LEDS, so you'll need two, but cascading them is very easy.

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1339

I've got driver code for the chip, running with the P89C51 processor .

Another part I've used is made by Allegro
http://www.allegromicro.com/en/Products/Part_Numbers/6832/index.asp
These are simpler to drive, but less functional., and you'll need four of 'em.

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sporkmasta (author)steveastrouk2009-08-11

Would it be hard to write code to run 2-3 cascaded MAX chips (I ordered 4 samples) from a Computer-->USB-->SPI output? I don't have much experience programming... But thanks for all the replies everyone!

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sporkmasta (author)steveastrouk2009-08-13

Probably will go usb-spi via the um245R. Nice find :-)

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steveastrouk (author)sporkmasta2009-08-14

Let me know if you need coding help with it - be aware the MAX 7221/19 start all Leds off.....

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sporkmasta (author)steveastrouk2009-09-03

Steve- I actually might need some coding help. Do you know any resources to help with the coding? Which language would you recommend? Thanks!

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steveastrouk (author)sporkmasta2009-09-03

What are you driving the chips with ? Just a PC ? Steve

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sporkmasta (author)steveastrouk2009-09-03

Going with : PC->UM245R->3 cascaded MAX7221's

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steveastrouk (author)sporkmasta2009-09-04

PM me and we'll look at it together. Steve

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frollard (author)steveastrouk2009-08-02

AAAAAAAAAAAAnnnd...maxim-ic will give you a couple samples for your project :D

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firebird982002 (author)2009-08-01

Your best bet is to use a micro controller. AVR chips and PIC chips are the most popular. Arduino, uses the AVR microcontroller, and has hundreds of tutorials online. Arduino only costs about $30, and is likely your cheapest way to do what you are looking to do. Check out www.arduino.cc and http://little-scale.blogspot.com/2008/01/32-led-fader-with-arduino.html .

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frollard (author)firebird9820022009-08-02

perhaps a suitable use of the new arduino ultramegasuperduper with tonnes of io :D

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orksecurity (author)2009-08-01

You might want to search Instructables for "charlieplexing". That will find a description of one approach to managing LED arrays, and I think it will also find some instructables which compare it to other approaches.

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jj37 (author)2009-08-01