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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

10 years ago

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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sporkmastasteveastrouk

Answer 10 years ago

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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steveastrouksporkmasta

Answer 10 years ago

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

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sporkmastasteveastrouk

Answer 10 years ago

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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frollardsteveastrouk

Answer 10 years ago

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

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frollardfirebird982002

Answer 10 years ago

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

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orksecurity

10 years ago

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

10 years ago

Look around 3:03