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'[EE]: Seeking serial LED Driver'
2000\10\31@185210 by Short, Evan

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Hello all,

I'm trying to drive an array of <= 16 LEDs from a PIC, hopefully using a
single surface mount part. Ideally, the part would directly drive the LEDs,
perhaps with an external resistor to set the constant current, and would be
serially controlled. The MM5450, which was a Micrel part but seems to have
been made by all sorts of people, was ideal for this, but it's a huge 40 pin
DIP. I've searched high and low and have been unable to find a single chip
solution for this; in the past I've used a shift register connected to a
transistor array connected to current limiting resistors connected to the
hip bone...
I don't need to multiplex anything, I just want to be able to individually
control a series of tiny SM LEDs with a single part (this all goes on a very
small board.)
I'd appreciate any ideas at all, especially if there is something I'm
missing.
Thanks,

Evan.

==========<O>==========
Evan Short
FERRARI  S.p.A. GES - Electronic dept.
v. Ascari 55/57   41053 Maranello (MO)   ITALY
Tel. +39 (536) 949.492   FAX +39 (536) 949.377
spam_OUTeshortTakeThisOuTspamferrari.it

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2000\10\31@190720 by David VanHorn

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Two HC164s works well.. Not a single part, but that would be at least a 20
pin package.  Two 14s might be easier to live with.

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2000\10\31@193040 by Dwayne Reid

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At 06:58 PM 10/31/00 +0100, Short, Evan wrote:
>Hello all,
>
>I'm trying to drive an array of <= 16 LEDs from a PIC, hopefully using a
>single surface mount part. Ideally, the part would directly drive the LEDs,
>perhaps with an external resistor to set the constant current, and would be
>serially controlled. The MM5450, which was a Micrel part but seems to have
>been made by all sorts of people, was ideal for this, but it's a huge 40 pin
>DIP. I've searched high and low and have been unable to find a single chip
>solution for this; in the past I've used a shift register connected to a
>transistor array connected to current limiting resistors connected to the
>hip bone...
>I don't need to multiplex anything, I just want to be able to individually
>control a series of tiny SM LEDs with a single part (this all goes on a very
>small board.)
>I'd appreciate any ideas at all, especially if there is something I'm
>missing.
>Thanks,

2 S0-16 parts:  74hc595 - each drives 8 LEDs.  Also requires current limit
resistors, which can be bussed SIPs if you have access to both sides of
each LED.

dwayne



Dwayne Reid   <.....dwaynerKILLspamspam@spam@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 16 years of Engineering Innovation (1984 - 2000)

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2000\10\31@195007 by Jinx

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From: Short, Evan <eshortspamKILLspamFERRARI.IT>

> serially controlled. The MM5450, which was a Micrel part but seems to
> have been made by all sorts of people, was ideal for this, but it's a huge
> 40 pin DIP.

The MM5450 is available as the smaller 44-pin PLCC

Maxim http://www.maximic.com may have LED drivers (other than the 7212
I'm familiar with)

> I don't need to multiplex anything, I just want to be able to individually
> control a series of tiny SM LEDs with a single part (this all goes on a
very
> small board.)

If it's individual LEDs you want to control, then possibly a couple of SMT
4051s might do, although they need ABC inputs. Would certainly cut down
the component count. Either that or 4017s (using just current-limiting Rs,
needs only one PIC pin to do both Clk and Reset) or LM3914/3915 drivers.
Oscillate a PIC pin into RC to get an analogue voltage. You could always
use high-efficiency LEDs to reduce current requirements

If the idea is to count how many times a year an F1-2000 049 can lap a
Minardi you'll need a damn sight more than 16 LEDs

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2000\10\31@200240 by Jinx

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> >I'm trying to drive an array of <= 16 LEDs from a PIC

Just thought, check the archives. Around a year ago there was a
prolonged discussion on (what started as) a 4x4 array using only
PIC pins. Don't recall how it ended up, but quite a few practical
suggestions re input/output/tri-state conditions to access any LED

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2000\10\31@200903 by Paul Hutchinson

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Major overkill but,

Maxim MAX7221

10MHz Serial Interface
SPI, QSPI, Microwire Serial Interface
24-Pin DIP and SO Packages
Digital and Analog Brightness Control

It can be used to drive up to 64 discrete LED's, 8 7-seg displays or, mix of
discretes and displays.

Paul

=========================================
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Chief Engineer
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New Bedford, MA 02745
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2000\10\31@202358 by Brian Aase

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Maxim MAX7219.  A bit pricey but fun to work with.
-----

On 31 Oct 2000, at 18:58, Short, Evan wrote:

{Quote hidden}

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2000\10\31@205149 by Andrew Warren

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Short, Evan <PICLISTspamspam_OUTMITVMA.MIT.EDU> wrote:

> I'm trying to drive an array of <= 16 LEDs from a PIC, hopefully
> using a single surface mount part. Ideally, the part would
> directly drive the LEDs, perhaps with an external resistor to set
> the constant current, and would be serially controlled. The MM5450,
> which was a Micrel part but seems to have been made by all sorts
> of people, was ideal for this, but it's a huge 40 pin DIP. I've
> searched high and low and have been unable to find a single chip
> solution for this; in the past I've used a shift register
> connected to a transistor array connected to current limiting
> resistors connected to the hip bone... I don't need to multiplex
> anything, I just want to be able to individually control a series
> of tiny SM LEDs with a single part (this all goes on a very small
> board.) I'd appreciate any ideas at all, especially if there is
> something I'm missing.

Evan:

Philips SAA1064:

   24-pin SO package (or 24-pin DIP)
   I2C interface
   controls up to 28 LEDs
   software-controlled current (i.e., brightness) up to 21 mA
   -40 to +85C for your presumably-automotive application

What are you building... Shift lights?  "Don't rev this high yet"
tach LEDs like the ones on the new BMW?  Something else?

-Andy


=== Andrew Warren --- @spam@aiwKILLspamspamcypress.com
=== Cypress Semiconductor Corporation
=== Interface Products Division, S.D.

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2000\10\31@205342 by David Covick

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Evan,

With 5 I/O's you can turn on and off 20 LED's with a PIC.
With out getting into specifics, 5 I/O's will do 10 LED's back to back.
With some fancy wiring the other 10 can be added in.
One resistor "can" set the current an all LED's in a simple arrangement.

Forget about adding another chip.

How many I/O's do you have available?

David



{Original Message removed}

2000\10\31@205749 by Bob Ammerman

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How many LEDs can be on at a time? If only 1, you can use a single current
limiting resistor:

Connect +V to one end of the resistor and the anodes of all the LEDs to the
other end of the resistor.

Now connect the cathode of each LED to a PIC pin. Unfortunately to get 16
LED's you'll need a 28pin PIC with this technique.

======

Or, if you are using high-efficiency LEDs, you can drive 16 from a PIC16C505
(14 pin DIP or SO package, internal RC) .

Set the LEDs up in a 4x4 matrix, include current limiting resistors on one
edge of the matrix.

The LED's use 8 i/o's on the PIC. The rest can be used for your serial
connection.

The code to drive this is relatively trivial.

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)


Bob Ammerman
RAm Systems
(contract development of high performance, high function, low-level
software)

{Original Message removed}

2000\10\31@224253 by Dwayne Reid

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At 05:52 PM 10/31/00 -0800, David Covick wrote:
>Evan,
>
>With 5 I/O's you can turn on and off 20 LED's with a PIC.
>With out getting into specifics, 5 I/O's will do 10 LED's back to back.
>With some fancy wiring the other 10 can be added in.
>One resistor "can" set the current an all LED's in a simple arrangement.

Umm... I mostly agree with you - but it takes *5* resistors, not just 1 to
control the current in all the LEDs.  The other problem is that LED current
is fairly low because you have to multiplex them - no more than 4 or 5 mA
average if you don't want to exceed the current rating on the pin.  But
that particular problem is easily fixed with the addition of 5 driver
transistors as follows:

You have several (4 or more) driver circuits driving a LED matrix.  The
resistor is the current limit when the PIC output is LO.  The transistor
provides current gain so that multiple LEDs can be turned on when its PIC
output is HI.  Unlit LEDs have the PIC output tristated during that portion
of the scan cycle.  Yes, the resistor also serves to keep the transistor
turned off when it is supposed to be off.  But you size the resistor
according to the desired LED current.

4 drivers will control 12 LEDs.  Up to 3 LEDs can be lit during each step
of the scan.  5 drivers will control 20 LEDs, with up to 4 LEDs being lit
during each part of the scan.  The transistors allow the number of scan
steps to be held to the number of driver stages without compromising LED
brightness.
              O +Vdd (can be unregulated supply so long as it is >= Vdd)
              |
             /
           |/
PIC o--+---|  NPN driver (2n4401 or similar)
       |   |V
       |     \
       |      |
       +-VVV--+-----o Matrix point
          R
So how about it, Evan.  David's suggestion is a good one.  Do you have 5
available i/o pins?  That will give you your 16 (up to 20) LEDs - cost is 5
resistors if you can live with only 4-5 mA LED current; add the 5
transistors and you can get the LED current up to 15 or 20 mA.

dwayne



Dwayne Reid   <KILLspamdwaynerKILLspamspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax

Celebrating 16 years of Engineering Innovation (1984 - 2000)

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Do NOT send unsolicited commercial email to this email address.
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'[EE]: Seeking serial LED Driver'
2000\11\01@005953 by Bill Westfield
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> >I'm trying to drive an array of <= 16 LEDs from a PIC

Most general solution: another PIC...

BillW

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2000\11\01@033522 by Adlam Frank

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TCL5920 is SMT part with current limiting via one resistor.  Minimum design,
small space, easy to use.  Currently using two of it to drive 100 bi-colour
LEDs in a bargraph display - multiplexing.

{Original Message removed}

2000\11\01@043738 by Bala Chandar

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-----Original Message-----
From: Adlam Frank [spamBeGoneFADLAMspamBeGonespamPETECH.AC.ZA]
Sent: Wednesday, November 01, 2000 2:04 PM
To: TakeThisOuTPICLISTEraseMEspamspam_OUTMITVMA.MIT.EDU
Subject: Re: [EE]: Seeking serial LED Driver


> TCL5920 is SMT part with current limiting via one resistor.  Minimum
design,
> small space, easy to use.  Currently using two of it to drive 100
bi-colour
> LEDs in a bargraph display - multiplexing.

That sounds very interesting! Can you please let me know more details about
TCL5920 (No. of pins, package, supply voltage, price, etc.)
Also, the website from where I can get the datasheet, please.

Thanks!

Bala Chandar

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2000\11\01@074330 by mike

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On Tue, 31 Oct 2000 18:58:19 +0100, you wrote:

>Hello all,
>
>I'm trying to drive an array of <= 16 LEDs from a PIC, hopefully using a
>single surface mount part. Ideally, the part would directly drive the LEDs,
>perhaps with an external resistor to set the constant current, and would be
>serially controlled. The MM5450, which was a Micrel part but seems to have
>been made by all sorts of people, was ideal for this, but it's a huge 40 pin
>DIP. I've searched high and low and have been unable to find a single chip
>solution for this; in the past I've used a shift register connected to a
>transistor array connected to current limiting resistors connected to the
>hip bone...
>I don't need to multiplex anything, I just want to be able to individually
>control a series of tiny SM LEDs with a single part (this all goes on a very
>small board.)
>I'd appreciate any ideas at all, especially if there is something I'm
>missing.
>Thanks,
>
Rohm do a number of LED driver type devices - not sure if they go up
to 16.
My old catalogue shows a 12 way driver in SSOP package and 20mA drive
(BU2099)

If all else fails use a small PIC like the 16C505 and multiplex the
LEDs - this will  probably be the smallest and cheapest solution, and
you could uyse async comms so only 1 data wire would be needed.

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2000\11\01@090627 by Olin Lathrop

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> I'm trying to drive an array of <= 16 LEDs from a PIC, hopefully using a
> single surface mount part.

How about a PIC with more pins?


*****************************************************************
Olin Lathrop, embedded systems consultant in Devens Massachusetts
(978) 772-3129, EraseMEolinspamcognivis.com, http://www.cognivis.com

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2000\11\01@122812 by Harold M Hallikainen

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       Who makes the TCL5920? A quick search didn't turn up anything.

Harold

On Wed, 1 Nov 2000 10:34:24 +0200 Adlam Frank <RemoveMEFADLAMspam_OUTspamKILLspamPETECH.AC.ZA>
writes:
> TCL5920 is SMT part with current limiting via one resistor.  Minimum
> design,
> small space, easy to use.  Currently using two of it to drive 100
> bi-colour
> LEDs in a bargraph display - multiplexing.
>

FCC Rules Online at http://hallikainen.com/FccRules
Lighting control for theatre and television at http://www.dovesystems.com

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2000\11\01@122816 by Harold M Hallikainen

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On Wed, 1 Nov 2000 12:44:01 +0000 Mike Harrison <EraseMEmikespamspamspamBeGoneWHITEWING.CO.UK>
writes:
>  If all else fails use a small PIC like the 16C505 and multiplex the
> LEDs - this will  probably be the smallest and cheapest solution,
> and
> you could uyse async comms so only 1 data wire would be needed.
>

       I'm doing that with a 16f627-04/SO on a 1x1.5 inch board. It drives 2 7
segment digits and sends back the state of one on-board switch and one
off-board switch.

Harold



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2000\11\01@175416 by Kyrre Aalerud

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From: "Short, Evan" <eshortSTOPspamspamspam_OUTFERRARI.IT>
Sent: Tuesday, October 31, 2000 6:58 PM
Subject: [PICLIST] [EE]: Seeking serial LED Driver
> Hello all,
>
> I'm trying to drive an array of <= 16 LEDs from a PIC, hopefully using a
> single surface mount part. Ideally, the part would directly drive the LEDs,
> perhaps with an external resistor to set the constant current, and would be
> serially controlled. The MM5450, which was a Micrel part but seems to have
> been made by all sorts of people, was ideal for this, but it's a huge 40 pin
> DIP. I've searched high and low and have been unable to find a single chip
> solution for this; in the past I've used a shift register connected to a
> transistor array connected to current limiting resistors connected to the
> hip bone...
> I don't need to multiplex anything, I just want to be able to individually
> control a series of tiny SM LEDs with a single part (this all goes on a very
> small board.)
> I'd appreciate any ideas at all, especially if there is something I'm
> missing.
> Thanks,

Why don't you do it simple for yourself...
smt shift registers that can handle 20 mA "open drain" and combine those with smt led's with buildt in current limiting resistors :-)
I have used this in a rather large LED-panel that I am building...  My only problem is the extreme ammount of current that all my LEDs draw.  (640 LEDs at 20 mA = 12.8 Amps!!!  Not nice on a surface track :-)
This solution will only need one chip per 8 or so LEDs...  You would need atleast 2 pins.  1 for data and 1 for clocking the shift regs... (But you know that :-)

The regs can handle any speed the PIC can so you would get a heck of an update rate...
My huge array can cope with clock speeds of 25 MHz, far abowe the PIC.

The expensive part is getting the LED's with current limitor.
(If you live in Norway, Sweden or Denmark you might get it at Elfa...)

   Good luck
   KreAture

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2000\11\01@191802 by jamesnewton

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Kyrre, are you going to spin those 640 LED around? or spin a mirror in front
of them? Is there shielding in place in case of a "mechanical
decomposition"? <grin>

Just curious. I've thought about it some at
http://www.piclist.com/../io/led/hud.htm
and
http://www.piclist.com/../idea/mscan/index.htm

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{Original Message removed}

2000\11\02@024513 by staff

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Bob Ammerman wrote:
{Quote hidden}

How about a compromise? Matrix two rows of 8 leds, easy to drive
with a 8-bit PIC. You can use two resistors, one for each row,
but keep in mind that the multiplexing must be done the other
way, 2 leds at a time over 8 cycles etc.

My preferred choice would be 2x8 matrix, driven as two bytes
alternating, but needs 8 resistors so I would one of those tiny
"strip" resistor packs from Farnell, with 8 resistors and one
common wire in a slimline 9 pin package not much bigger than
one resistor. Using 2x8 means 10 I/O lines, but almost any
14/16pin PIC will do that.
-Roman

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2000\11\02@060851 by Adlam Frank

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Sorry, it is the TLC5920 16x8 BIT LED DRIVER/CONTROLLER by Texas
Instruments.  I apologise for giving the incorrect part number.  Enjoy!
Mail me if you want the datasheet!

{Original Message removed}

2000\11\02@120140 by Harold M Hallikainen

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       OK, that part number works. I was expecting a chip with a bit more
integration. It looks like the column multiplexing must still be
controlled by the host processor (driving the CSEL lines while sending
the 16 bit column data serially between columns). I'd kinda expect it to
just have a 512 bit shift register that you load and the chip handles the
rest on its own.


Harold


On Thu, 2 Nov 2000 13:03:17 +0200 Adlam Frank <@spam@FADLAM@spam@spamspam_OUTPETECH.AC.ZA>
writes:
> Sorry, it is the TLC5920 16x8 BIT LED DRIVER/CONTROLLER by Texas
> Instruments.  I apologise for giving the incorrect part number.
> Enjoy!
> Mail me if you want the datasheet!
>
> {Original Message removed}

2000\11\02@130847 by Jay.R.Vijay-Indra

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Try Allegro A6276 is a 24 pin 16 LED driver with serial input and single
external resister to control the LED current. The device has input latch
and output tri-state. A6276 is available in 24 pin DIL or SOIC.

If you can't find the data sheet contact me off the list

Regards,

Jay


At 18:58 31/10/00 +0100, you wrote:
{Quote hidden}

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2000\11\02@170853 by Chris Carr

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----- Original Message -----
From: "Andrew Warren" <TakeThisOuTaiw.....spamTakeThisOuTCYPRESS.COM>
To: <TakeThisOuTPICLISTKILLspamspamspamMITVMA.MIT.EDU>
Sent: Wednesday, November 01, 2000 1:35 AM
Subject: Re: [EE]: Seeking serial LED Driver


{Quote hidden}

Toshiba manufacture a series of parts
go to http://www.semicon.toshiba.co.jp/indexus.htm

click on "General-Purpose Linear ICs"
then scroll down to "Interface Drivers" and select
"LED Panel & Printer..........."
the following should take you directly there...........maybe

http://www.semicon.toshiba.co.jp/seek/us/td/06linia/060021.htm

availability may be a problem. They are not available in the UK
but they can be sourced from Japan at a reasonable price.

Regards
Chris

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