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Beginner needs help with large led display — Parallax Forums

Beginner needs help with large led display

wilsoewilsoe Posts: 6
edited 2005-11-15 15:10 in BASIC Stamp
I have a question about building a digital timer with a very large led display.· (Like experiments #29 and #30 in Stampworks Manual.)· I have been looking everywhere for some examples and could not find any.· I am wanting to use Jameco's 202534cj (mfr. # lsd50055-20) 5" common cathode led displays.· It is rated at 17Vf @ 20mA.· My question is how do I power the display using the bs2 with the max7219 or is another design necessary?
Thanks,
Eric

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2005-11-15 15:10
    Eric,

    ·· You have two options...The first is that Maxim/Dallas has an AppNote for the MAX7219 (I think it's AN1196) that tells how to drive high-voltage/current displays.· You can find it on their website in the AppNote section for the MAX7219.

    ·· Second option...Use a Common Anode Display instead, and drive the cathodes with a ULN2803/74HC595 system.· Then you can have pattern lookups for the segments and shift them out to the displays.· If you're interested in this, I can explain it more, but Jon Williams has some sample codes floating around for looking up seven-segment patterns from EEPROM and sending them out to a display.· Only difference here is the ULN2803 and possibly using shift registers.

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    Chris Savage
    Parallax Tech Support
    csavage@parallax.com
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