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MAX7219 Rset help — Parallax Forums

MAX7219 Rset help

TCTC Posts: 1,019
edited 2013-12-04 09:54 in General Discussion
Hello all,
I have been trying for hours to find out how Maxim came up with the Rset table on page 11 of the data sheet for the MAX7219. I have to figure out how to drive displays and individual LEDS that have different forward voltages and currents. I have an idea in my head, but it will only work when I find out how they came up with that table. PLEASE HELP

Thanks
TC

datasheets.maximintegrated.com/en/ds/MAX7219-MAX7221.pdf

Comments

  • Buck RogersBuck Rogers Posts: 2,185
    edited 2013-12-02 14:31
    TC wrote: »
    Hello all,
    I have been trying for hours to find out how Maxim came up with the Rset table on page 11 of the data sheet for the MAX7219. I have to figure out how to drive displays and individual LEDS that have different forward voltages and currents. I have an idea in my head, but it will only work when I find out how they came up with that table. PLEASE HELP

    Thanks
    TC

    datasheets.maximintegrated.com/en/ds/MAX7219-MAX7221.pdf


    Hello!
    Okay where. Please show us.
  • TCTC Posts: 1,019
    edited 2013-12-02 14:44
    Buck Rogers wrote: »
    Hello!
    Okay where. Please show us.

    Im sorry, what do you mean "please show us"?
    The data sheet only shows the table (which is different from the 1992 version of the data sheet bundled with Parallax "AppKit page 20 MAX7219-21 8-Digit LED Display Driver-1.pdf.) But no formula to figure out the correct value of Rset.
    pdf
    pdf
    MAX7219-21 8-Digit LED Display Driver-1.pdf
    551K
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2013-12-03 17:01
    TC, the table gives the resistor value in KOhms based on the forward voltage of the LEDs versus the current you want to run through them. Do you need a value outside of this range?
  • TCTC Posts: 1,019
    edited 2013-12-03 17:16
    No, I Thought I had two different forward currents that I had to drive. Then after a MAXIM engineer opened my eyes that I was looking at the wrong data sheet( Felt like an idiot) for my displays, I found out that everything I am driving all use the same value.
  • SavageCircuitsSavageCircuits Posts: 257
    edited 2013-12-03 19:37
    So you're set then?
  • TCTC Posts: 1,019
    edited 2013-12-04 03:16
    Yes I am, Thank you and sorry for wasting everyone's time
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2013-12-04 09:16
    It's never a waste of time when you need help or don't understand something as long as you take something away from it. Feel free to post your questions here and we'll always do our best to answer. :thumb:
  • PublisonPublison Posts: 12,366
    edited 2013-12-04 09:54
    +1 ..........................
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