LED Driver / PIC Help

Discussion in 'The Projects Forum' started by duttydea, Feb 26, 2010.

  1. duttydea

    Thread Starter New Member

    Feb 26, 2010
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    I have an Arduino with 48 Analog inputs from 3 Multiplexers. Each input is connected to either a Linear Fader or a Potentiometer to read the output of the original 5V.

    Using an I2C Volume control chip & MIDI out i'm hopping to Make a Controller

    I am trying to find a IC that will light 10? led based on a 0V - 5V current rather than programming a multiplexer and using even more I/O of the controller.

    Has anyone got any ideas or suggestions?

    Thanks in Advance
     
  2. John P

    AAC Fanatic!

    Oct 14, 2008
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    The way to run a few LEDs with relatively few processor pins is to use a shift-register design. You'd need 3 processor pins, but if you already have SPI (I'm not so sure about I2C) then most likely only 1 extra would be needed. The 74HC595 chip is the one most commonly used for this, with each 595 driving 8 LEDs.

    The drawback is that each LED needs its own resistor and that can be a lot of wiring. You could use a specialized driver chip like the MAX7219, which can drive 64 LEDs with one resistor setting the brightness for all of them, but it costs $14.
     
  3. duttydea

    Thread Starter New Member

    Feb 26, 2010
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    Thanks for the response!!

    Ideally i would like a stand-alone IC, I will be adding a "VU" Like Meeter to each channel.

    Programming and wiring 480 leds to the arduino seems like over kill and a drain on the arduino's resources.

    Can a PIC be programed to do this job?

    Thanks in Advance
     
  4. BMorse

    Senior Member

    Sep 26, 2009
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  5. SgtWookie

    Expert

    Jul 17, 2007
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    If you're only going to have 10 LEDs per channel, use the LM3916 like BMorse suggested.
    If you want more than 10 LEDs per channel, use the LM3915.
    The LM3914 won't really be suitable for an audio spectrum display.
     
  6. duttydea

    Thread Starter New Member

    Feb 26, 2010
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    Cheers Guys!!
    Im going to buy a a load of LM3914


    The Volume IC basically attenuates the analog volume via I2C/SPI Commands.
    Cirrus Logic CS3308/18

    High-Performance 8-Channel Analog Volume Control

    http://www.cirrus.com/en/pubs/proDatasheet/CS3308_F1.pdf

    I just got to figure out how to convert fader movement into I2C.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    You do not want an LM3914 for audio. It has a linear response.

    You need a log or VU-type response.

    That is why I suggested the LM3915 if you are going to cascade them (over 10 LEDs) or the LM3916 for 10 LEDs.
     
  8. duttydea

    Thread Starter New Member

    Feb 26, 2010
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    Cheers for the pointers,
    But the "VU" is not audio based.

    It will just be a visual representation of the what the Pot is is doing to the to the 5V.
     
  9. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    I guess all those old Volume Unit meters in every broadcast station were for decoration.
     
  10. BMorse

    Senior Member

    Sep 26, 2009
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    the op is referring to his application.... he is using them to display the wiper position of a linear fader and/or potentiometer (0 to 5 volts range).... not for displaying an audio VU Meter.....:cool:

    ....:rolleyes:
     
  11. duttydea

    Thread Starter New Member

    Feb 26, 2010
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    My Overall project is a 500 Series Modular Mixing

    A mate of mine designs 500 Series Moules (Amp, EQ's etc..) and is tryin to buuild mixer in this format!!

    Idealy he wants Fader Recall (Motorised Faders) but for now were experimenting with the I2C Volume Control as an Aux Box..

    [​IMG]
     
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