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'4 digits.'
1996\08\30@094025 by Mark A. Corio

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Hi all,

Does anyone know of a 7-segment LED driver that is serial loaded?  I need to
drive 4 digits from a PIC and don t want to use a lot of pins?  Any other way
to do this?  The cheaper the better (of course).
Thanks.

Mark A. Corio
Rochester MicroSystems, Inc.
200 Buell Road, Suite 9
Rochester, NY  14624
Tel:  (716) 328-5850 --- Fax:  (716) 328-1144
http://www.frontiernet.net/~rmi/

***** Designing Electronics For Research & Industry *****

1996\08\30@095714 by Andy Errington

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Yes,

National Semiconductors MM5450N 34 segment LED driver chip (7seg+dp x 4
= 32, leaves 2 for a colon or other indicators)

These chips are available blobbed onto 4 digit display modules from
III-V systems, either 4x0.3" with 2 external indicators or 4x0.5" with
colon.

Maxim, Harris and Nat. Semi. also do a range of serial in, 8 digit
multiplexed out driver chips, if you want 8 digits (or 64 bargraph
elements).

Andy (the other one)

{Quote hidden}

1996\08\30@100337 by mike

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In message  <.....960830093919_273132284KILLspamspam@spam@emout12.mail.aol.com> PICLISTspamKILLspamMITVMA.MIT.EDU
writes:
> Hi all,
>
> Does anyone know of a 7-segment LED driver that is serial loaded?  I need to
> drive 4 digits from a PIC and don t want to use a lot of pins?  Any other way
> to do this?  The cheaper the better (of course).
> Thanks.
>

It may be considered overkill, but you could use an 18 pin PIC
to drive the LEDs. You could accept data on a one wire interface
(like rs232) so your main application PIC will lose only one pin.

Regards,


Mike

1996\08\30@111904 by Keith Dowsett

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>Hi all,
>
>Does anyone know of a 7-segment LED driver that is serial loaded?  I need to
>drive 4 digits from a PIC and don t want to use a lot of pins?  Any other way
>to do this?  The cheaper the better (of course).
>Thanks.

National Semiconductor make the MM5450 which will run four digits, or eight
if multiplexed. Only needs an external brightness resistor, data and clock
lines.

Phillips make the SAA1064 which will run four digits as two multiplexed
pairs It has an I2C interface but might be closer to your requirements.

Hope this helps,

Keith
==========================================================
Keith Dowsett         "Variables won't; constants aren't."

E-mail: .....kdowsettKILLspamspam.....rpms.ac.uk
WWW:    http://kd.rpms.ac.uk/index.html

1996\08\30@113117 by Pedro

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Hi,

I use Motorola MC14489.
It can drive 5 digits, 4 digits and 4 Leds, 3 and 8 ...
You simply need 3 wires: SClock,Sdata and Enable.
You can controll segment currents with only one resistence.

Hope this helps!

Renato Ferreira
Portugal

1996\08\30@113337 by myke predko

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Mark,

When I saw your request, I thought of what Andy suggested.

I can provide you with code for driving the LEDs.  You could do it with a
16C61 OTP ($6.15 each in single quantities from Digi-Key), four transistors
and seven (or 8 if you want to use the decimal points) resistors.

Myke
{Quote hidden}

Do you ever feel like an XT Clone caught in the Pentium Pro Zone?

1996\08\30@132628 by maud

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Mark A. Corio wrote:
>
> Hi all,
>
> Does anyone know of a 7-segment LED driver that is serial loaded?  I need to
> drive 4 digits from a PIC and don t want to use a lot of pins?  Any other way
> to do this?  The cheaper the better (of course).
> Thanks.
>
> Mark A. Corio
> Rochester MicroSystems, Inc.
> 200 Buell Road, Suite 9
> Rochester, NY  14624
> Tel:  (716) 328-5850 --- Fax:  (716) 328-1144
> http://www.frontiernet.net/~rmi/
>
> ***** Designing Electronics For Research & Industry *****


Try the Motorola MC14499
Easy to use, economical, ideal for your app.

1996\08\30@201038 by William J Kitchen

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On Fri, 30 Aug 1996 09:39:21 -0400 "Mark A. Corio" <Mcoriospamspam_OUTAOL.COM>
writes:
>Hi all,
>
>Does anyone know of a 7-segment LED driver that is serial loaded?  I
need to
>drive 4 digits from a PIC and don t want to use a lot of pins?  Any
other way
>to do this?  The cheaper the better (of course).  Thanks.

You might want to consider the 5450 or 5451 from Micrel.  It is a 34 or
35 segment LED display driver that works like a large shift register.
The outputs are latched so that data does not appear on the display
while shifting in.  Display brightness can be controlled by a single
resistor.  All segments are controlled individually, so it's very
flexible.  You can get info on this from Micrel's web page
(http://www.micrel.com).


                                       Peace,
                                       William Kitchen

1996\08\31@005717 by Rusu Dan Victor

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Mark:

I' am using Philips SAA 1064. This IC can drive 4 digits and it has a I2C
interface. Here, in Romania, it cost aprox. $2.5. I'm sure you can find a
ceaper source!

Dan

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dan-Victor RUSU                         Technical University of Cluj
                                       Computer Science Department
@spam@rdvKILLspamspamutcluj.ro                           Baritiu, 26 Cluj-Napoca, ROMANIA
http://www.utcluj.ro/~rdv               Fax: (+40) 64 194491
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
On Fri, 30 Aug 1996, Mark A. Corio wrote:

{Quote hidden}

1996\08\31@023255 by Peter Grey

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At 09:39 AM 30/08/96 -0400, you wrote:

Mark,
You could use the Phillips PCF8574 (I2C to 8 I/O expander)to give you the
drive for the segments and another 4 pins for the other side of the
segments(common). Alternatively, another PCF8574 could be used meaning that
only 2 PIC pins were used. I do not know of any serial loaded 7 segment LEd
driver.

Good luck,


{Quote hidden}

Peter Grey
Neosystems, Australia


'4 digits.'
1996\09\06@013635 by gary skinner
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If you don't want the LEDs multiplexed
A simple output expander is a LS595 serial in parallel out shift register.
It has a pin for chaining them together.
The 599 has open collector outputs, but I have never seen one.

TI makes a version of this in their power+ line that has
power DMOS outputs.

hope this helps...
Gary Skinner
Gary Skinner,  Electronic Solutions Inc
Design of custom control circuits
Denver CO  303-469-9322

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