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Multiple LED status indicators — Parallax Forums

Multiple LED status indicators

ArchiverArchiver Posts: 46,084
edited 2003-11-13 00:56 in General Discussion
I have a project where I need to be able to light about 120 LEDs as status
indicators. I will need to be able to choose any individual LED and determine
whether it is to be lit or not, and I need the circuitry to drive them. I guess
a simple memory latch with a multiplex/driver scheme makes most sense? I would
like to be able to send all the data on a single line, or as few lines as
possible. Anyone recommend any particular chips to use for this purpose?
TIA,
David Reaves


[noparse][[/noparse]Non-text portions of this message have been removed]

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-11-12 10:57
    Hi
    Maybe some 15 cascaded '595 serial to parallel latches may do it.
    The '595 have the neccessary pins to cascade them. It would require
    just a single serial line (synchronous) to send a string of 120 bits -
    plus an other line to transfer the shiftregister contents to the
    outputs (latch).
    The '595 are 8bit, maybe there is a different style with 16bit or so.
    Regards
    Adrian
  • ArchiverArchiver Posts: 46,084
    edited 2003-11-12 15:17
    Yup, the '595 is the chip to use for this.
    I believe it has the required current output on-chip
    also, so you won't have to use any additional
    drivers with the LED's. I recommend DIP factor
    current limiting resistors for size and neatness.

    Each '595 can control 8 LED's. They can be wired
    into a full string of 15 chips, or you can
    'split strings' to provide faster updates.

    At the 1 uS cycle clock of 'SHIFTOUT', you can
    update all 120 LED's in 120 uSec or so. You'll
    need 15 bytes to store the info -- which the BS2
    has.

    Sounds like a cool project!

    --- In basicstamps@yahoogroups.com, rrsounds@a... wrote:
    > I have a project where I need to be able to light about 120 LEDs as
    status
    > indicators. I will need to be able to choose any individual LED and
    determine
    > whether it is to be lit or not, and I need the circuitry to drive
    them. I guess
    > a simple memory latch with a multiplex/driver scheme makes most
    sense? I would
    > like to be able to send all the data on a single line, or as few
    lines as
    > possible. Anyone recommend any particular chips to use for this
    purpose?
    > TIA,
    > David Reaves
    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-11-12 16:12
    The UCN5833 is a 40 pin chip with 32 outputs (latched, open collector
    up to 40 volts, 125 ma each). It easily interfaces with the Stamp
    using SHIFTOUT, and multiple UCN5833s can be chained together.


    http://www.allegromicro.com/sf/5833/

    -- Tracy



    >I have a project where I need to be able to light about 120 LEDs as status
    >indicators. I will need to be able to choose any individual LED and determine
    >whether it is to be lit or not, and I need the circuitry to drive
    >them. I guess
    >a simple memory latch with a multiplex/driver scheme makes most sense? I would
    >like to be able to send all the data on a single line, or as few lines as
    >possible. Anyone recommend any particular chips to use for this purpose?
    >TIA,
    >David Reaves
    >
    >
    >[noparse][[/noparse]Non-text portions of this message have been removed]
    >
    >
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  • ArchiverArchiver Posts: 46,084
    edited 2003-11-12 16:41
    In a message dated 11/12/2003 11:22:26 AM Eastern Standard Time,
    tracy@e... writes:


    > The UCN5833 is a 40 pin chip with 32 outputs (latched, open collector
    > up to 40 volts, 125 ma each). It easily interfaces with the Stamp
    > using SHIFTOUT, and multiple UCN5833s can be chained together.
    >

    Good heavens, Tracy!! That is over 4 billion combinations per chip!

    If he needs four daisy-chained, that could be a programming nightmare.

    Sid


    [noparse][[/noparse]Non-text portions of this message have been removed]
  • ArchiverArchiver Posts: 46,084
    edited 2003-11-13 00:56
    Have a look at the various Maxim drivers such as the MAX6954, it can
    control 128leds I do believe. Maxim makes quite a few led based
    shift registers so have a look through their site. There are
    tutorials in the Nuts/Volts column on Parallax's website for the
    MAX7219 driver that will give you some insight as well as the
    application notes on Maxim's site.

    http://www.maxim-ic.com/Display.cfm

    Resc.






    --- In basicstamps@yahoogroups.com, Newzed@a... wrote:
    > In a message dated 11/12/2003 11:22:26 AM Eastern Standard Time,
    > tracy@e... writes:
    >
    >
    > > The UCN5833 is a 40 pin chip with 32 outputs (latched, open
    collector
    > > up to 40 volts, 125 ma each). It easily interfaces with the
    Stamp
    > > using SHIFTOUT, and multiple UCN5833s can be chained together.
    > >
    >
    > Good heavens, Tracy!! That is over 4 billion combinations per
    chip!
    >
    > If he needs four daisy-chained, that could be a programming
    nightmare.
    >
    > Sid
    >
    >
    > [noparse][[/noparse]Non-text portions of this message have been removed]
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