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I'm about to start working on a project that involves a long string of LED's used to light up the keys on a full piano. I plan to control what keys are lit up using software on my PC. This will be my first Arduino project, and I've looked at tutorials like this:

http://www.arduino.cc/en/Tutorial/ShiftOut

For driving many LED's. In this care I'll probably have around 50-60 LED's I want to control. Am I best daisy-chaining these LED shift register chips or is there a better way? If I should use these chips, where's the best place to buy them? (Are there any free samples)?

Thanks so much.
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I'm about to start working on a project that involves a long string of LED's used to light up the keys on a full piano. I plan to control what keys are lit up using software on my PC. This will be my first Arduino project, and I've looked at tutorials like this:

http://www.arduino.cc/en/Tutorial/ShiftOut

For driving many LED's. In this care I'll probably have around 50-60 LED's I want to control. Am I best daisy-chaining these LED shift register chips or is there a better way? If I should use these chips, where's the best place to buy them? (Are there any free samples)?

Thanks so much.

It should be okay to daisy-chain that long, but you also do a sort of parallel configuration, one or two shift register per IO line, and all the enables connected together.

Will this project use the LEDs to show you what notes to play?
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It will be used to show what notes to play.
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It will be used to show what notes to play.
Piano Hero! smiley-grin

--Phil.
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I'm about to start working on a project that involves a long string of LED's used to light up the keys on a full piano. I plan to control what keys are lit up using software on my PC. This will be my first Arduino project, and I've looked at tutorials like this:

http://www.arduino.cc/en/Tutorial/ShiftOut

For driving many LED's. In this care I'll probably have around 50-60 LED's I want to control. Am I best daisy-chaining these LED shift register chips or is there a better way? If I should use these chips, where's the best place to buy them? (Are there any free samples)?

Thanks so much.

Rather than making a chain of 50-60 of them (why not 88?) you'd be better off creating a matrix.  The easiest way is probably to consider each octave a column, and each key within an octave a row.  To light a key, make row high and column low.  This is similar to the "LED Cube" strategy.  That way you'll only need (rows+columns) pins/bits - 12+8 for a standard 88 (7 octaves plus).  That's 20, so you'll need a chain of three 595s, and three bytes/shifts.

Shift registers are cheap - like $1.50 for 8 bits.  You might also consider a MAX7219,  though it'll only drive 64 (8x8) bits.

You're going in the right direction, tho.
« Last Edit: April 09, 2008, 12:33:52 pm by justfred » Logged

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How many leds can I use with this circuit from  http://www.arduino.cc/en/Tutorial/ShiftOut
in the website, it shows up to two sets, but is there any problem of using more? what about the mA usage, will arduino support all that?
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If you've got the LEDs on a different chip, you'll have to make sure that chip can source all the current nesseracy to drive the LEDs, not the Arduino. smiley-wink You could also use transistors to switch the LEDs and you wouldn't have to worry about what the chips can provide for the most part.
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How many leds can I use with this circuit from  http://www.arduino.cc/en/Tutorial/ShiftOut
in the website, it shows up to two sets, but is there any problem of using more? what about the mA usage, will arduino support all that?

With the 595, there's only ever 8 LEDs on at a time.

http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1185507207/45#45

The code gets processed so fast, it "looks" like all the LEDs are on, so you can piggy-back as many 595's as you need, per the code in the link above smiley
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