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Shiftout variable modifiers, 7 Segment Displays — Parallax Forums

Shiftout variable modifiers, 7 Segment Displays

ArchiverArchiver Posts: 46,084
edited 2003-01-26 21:30 in General Discussion
Thanks, Tracy, Adrian...
Glad to hear it wasn't entirely my fault!

BTW, this ties into the 7 segment display discussion, in that the device I'm
communicating with is a Micrel MM5450BN from Jameco (www.jameco.com). This
device will drive up to 35 segments or individual LEDs with a simple 3-wire
interface. As I think someone else has stated, you have to be careful of
current draw with this many LED's. I'm overdriving the LED display I'm using
at 35-40 mA, and this thing sucks 600 mA, threatening to overheat my voltage
regulator. Fortunately, the duty-cycle's pretty low, so heat buildup remains
controllable.
The current displays I'm using only put out about 100 mcd, even with the
overdriving I'm doing. Does anyone know of any 7-segs which'll do 500-3000
mcd? I'm using these outside and the current ones are only barely visible if
you shield them with your hand. Thanks!

- Robert

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2003-01-25 17:09
    Hi Robert:

    I'm also working on an alphanumeric display using the same Allegro 6276. It
    would use standard T 1 3/4 type LEDs so could be stuffed with whatever
    brightness LED you desire. There are 64 LEDs for one digit that's about 3.5"
    high.

    Do you know what mcd rating of LED you need to see the display outside?

    Thanks,

    Brooke Clarke, N6GCE
    http://www.prc68.com

    Message: 6
    Date: Fri, 24 Jan 2003 20:04:26 -0700
    From: "Robert Ussery" <uavscience@f...>
    Subject: Re: Shiftout variable modifiers, 7 Segment Displays

    Thanks, Tracy, Adrian...
    Glad to hear it wasn't entirely my fault!

    BTW, this ties into the 7 segment display discussion, in that the device I'm
    communicating with is a Micrel MM5450BN from Jameco (www.jameco.com). This
    device will drive up to 35 segments or individual LEDs with a simple 3-wire
    interface. As I think someone else has stated, you have to be careful of
    current draw with this many LED's. I'm overdriving the LED display I'm using
    at 35-40 mA, and this thing sucks 600 mA, threatening to overheat my voltage
    regulator. Fortunately, the duty-cycle's pretty low, so heat buildup remains
    controllable.
    The current displays I'm using only put out about 100 mcd, even with the
    overdriving I'm doing. Does anyone know of any 7-segs which'll do 500-3000
    mcd? I'm using these outside and the current ones are only barely visible if
    you shield them with your hand. Thanks!

    - Robert

    > Date: Fri, 24 Jan 2003 17:33:51 -0800
    > From: Brooke Clarke <brooke@p...>
    > Subject: Re: Digest Number 1607
    >
    > Hello Sadler:
    >
    > I have been using the Allegro 6276 with a PIC, but there are no timing issues
    so it should work fine with a stamp.
    > http://www.allegromicro.com/sf/6276/
    >
    > This is a serial in chip that will drive 16 LEDs, 2 each 7-segment displays
    (including the decimal point) or one 14 or 16 segment alphanumeric LED display.
    The displays must be Common Anode since the 6276 contains a current sinking
    regulator for each LED. Note that the LEDs are driven in a static way, NOT
    multiplexed. There is a single resistor used to set the current for all 16
    LEDs. Note that multiplexing requires higher drive current [noparse][[/noparse]by SQRT(n)] then Dc
    drive and is less efficient.
    >
    > The 4 drive lines are: Data In, Clock In, Output Enable and Latch Enable.
    There is also a Data Out so the chips can be cascaded. In my case I tie the
    Latch Enable high and only use 3 I/O pins to drive as many digits as I want.
    >
    > I have a PCB on order that will hold 6 each 0.56" char. ht. 7-segment LEDs and
    the 3 each 6276 chips. The board is designed so that they can be cascaded using
    8 pin headers to form displays of 6, 12, 18, 24 digits, or whatever. Of course
    the power for the LEDs needs to be adequate. I'm thinking of also making boards
    for larger LEDs. You can see a 6 digit clock using this method of display at:
    http://brooke.mystarband.net/images/67576E.jpg Note the small number of parts
    needed.
    >
    > MAX7219 $ 3.99 @ 1,000
    > A6276 $ 1.29 @ 1,000
    >
    > If you're interested in any of these boards please let me know.
    >
    > Thanks,
    >
    > Brooke Clarke, N6GCE
    > http://www.prc68.com
    >
    > > Date: Fri, 24 Jan 2003 14:21:24 -0500
    > > From: Sadler Porter <porter.sadler@s...>
    > > Subject: 7 Segment Displays
    > >
    > > Is there a chip which decodes byte or nibble to 7 segment displays and
    > > handle the repeated strobing of the digit display .
    > > I want to write out 4 characters to a set of 4x 7 segs using a stamp and not
    > > worry about the overhead
  • ArchiverArchiver Posts: 46,084
    edited 2003-01-26 21:30
    > I'm also working on an alphanumeric display using the same Allegro 6276.
    It would use standard T 1 3/4 >type LEDs so could be stuffed with whatever
    brightness LED you desire. There are 64 LEDs for one digit >that's about
    3.5" high.

    I'll probably end up doing the same thing. The display I need is from .5-1"
    tall, so i could probably get away with using 3 or so T1-3/4 LED's per
    segment.

    > Do you know what mcd rating of LED you need to see the display outside?

    I don't know exactly. I would suspect >800 mcd to be really visible. Right
    now, I'm overdriving a 20 mcd display to about 40 mA per segment and it's
    just barely visible in direct sunlight and is not readable.

    - Robert
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