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'[PICLIST] [pic] LED dot matix dsiplay'
2000\11\13@102839 by Shahier Razik

picon face
Thanks everyone for the quick reply. I need a matrix that will fit 10-12
characters(I'm thinking a 7x10), is that enough?
As for the battery, I need to minimize the power for the longest possible
battery life. But for starters I'm not concerned with that yet.

I need to figure out the matrix size first, and where i can get it

Thanks

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2000\11\13@103704 by Michael Rigby-Jones

flavicon
face
Standard characters used in e.g. LCD displays use a 5x7 arrangement per
character which is about as small as you can get without making some
characters illegible.  You could maybe get away with 4x5, but that would be
a very chunky looking font!  Realisticaly you are only going to fit 2,
perhaps even 3 characters into a 7x10 array.

Mike
> {Original Message removed}

2000\11\13@120108 by Shahier Razik

picon face
So how can I fit more characters without using a large array???


>From: Michael Rigby-Jones <.....mrjonesKILLspamspam.....NORTELNETWORKS.COM>
>Reply-To: pic microcontroller discussion list <EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>
>To: PICLISTspamspam_OUTMITVMA.MIT.EDU
>Subject: Re: [pic] LED dot matix dsiplay
>Date: Mon, 13 Nov 2000 15:37:03 -0000
>
>Standard characters used in e.g. LCD displays use a 5x7 arrangement per
>character which is about as small as you can get without making some
>characters illegible.  You could maybe get away with 4x5, but that would be
>a very chunky looking font!  Realisticaly you are only going to fit 2,
>perhaps even 3 characters into a 7x10 array.
>
>Mike
> > {Original Message removed}

2000\11\13@124648 by Shahier Razik

picon face
Is it possible to find a smaller dot diameter???


{Quote hidden}

> > > > {Original Message removed}

2000\11\13@125927 by M. Adam Davis

flavicon
face
I'm confused by what you mean.  when I say '5x7 matrix' I am talking about
putting 35 LEDs in 7 rows of 5 LEDs each:
* * * * *
* * * * *
* * * * *
* * * * *
* * * * *
* * * * *
* * * * *

You can get leds to a very small diameter, and make a very tiny display.
Likewise, you can get leds which actually have several leds inside them
and have a large diameter.  Depending on the LED size and the spacing you
can have a tiny display (5mm (less than 1/4 inch) high per character) to a
very large display (300mm (one ft) high per character) or larger or
smaller.

You can also get a pre-built LED matrix display (like above) so you don't
have to wire the entire display yourself.

What is it you're trying to do?

-Adam

Shahier Razik wrote:
{Quote hidden}

> > > > > {Original Message removed}

2000\11\13@134313 by Bill Westfield

face picon face
>>    Is it possible to find a smaller dot diameter???

Sure.  You can get little dot-matrix LED displays with several characters
worth of dots in a package the size of a 14pin DIP or so.  The logic content
of these vary from not-much-more than LED drivers to drivers and shift
registers to full ascii compatibility (including character generators.)
On the minus side, these tend to be several 5x7 arrays (separate characters)
rather than a single Nx7 matrix.

See, for instance, the Agilent HCMS-291x.  One of the current projects I
have in mind for my spare time is PIC and/or AVR serial-LED style display
using some (variable number) of these...

Be aware that even with tiny LEDs, any reasonable number of digits ends up
consuming quite a LOT of power compared to a PIC or LCD display.

BillW

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2000\11\13@145614 by Byron A Jeff

face picon face
>
> Thanks everyone for the quick reply. I need a matrix that will fit 10-12
> characters(I'm thinking a 7x10), is that enough?

No. Not even enough for a scrolling display. You need to have enough
context for someone to read.

Think one character per 5x7 matrix. At least 5 characters for scrolling
context. So probably 25x7 minimum.

> As for the battery, I need to minimize the power for the longest possible
> battery life. But for starters I'm not concerned with that yet.

You have to be concerned with it. Point blank: LED's suck power. And for
brightness they need even more power. Especially when the display is
multiplexed.

Take the 25x7 example above. If you power a row at a time, you can have
up to 25 LED's on at the same time. For adequate brightness, you'll need
probably 100ma per LED. Totals out to 2.5A right off the top.

Even if you do it one column at a time it'll still be costly. Since the
refresh rate will be less than the rows, you'll have to apply even more
power to the LEDs to get adequte brightness (150-200ma each). It's still going
to be well more than an amp of power to drive them.

Batteries and LED's don't mix. Try a simple test: take a 9V battery and
drive an LED continously through a 470 ohm resistor (20 ma). See how long
it stays on.

BAJ
>
> I need to figure out the matrix size first, and where i can get it

As for where you can get matrixes, check out http://www.bgmicro.com and http://www.mpja.com.
Both are surplus houses that sell LED matrixes for reasonable prices.

BAJ
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2000\11\13@173031 by Bob Ammerman

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----- Original Message -----
From: Shahier Razik <KILLspamsrazik00spamBeGonespamHOTMAIL.COM>
To: <EraseMEPICLISTspamEraseMEMITVMA.MIT.EDU>
Sent: Monday, November 13, 2000 12:46 PM
Subject: Re: [pic] LED dot matix dsiplay


> Is it possible to find a smaller dot diameter???

B. G. Micro  (http://www.bgmicro.com) sells a 4 character 4 x 7 LED display which
is the size of a 16-pin DIP. They can be stacked end-to-end to make any
length display.

These chips actually decode ASCII and display the corresponding characters.

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

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2000\11\13@173036 by Bob Ammerman

picon face
You can get/create a decent non-proportional font, including space between
the characters at 6 wide x 7 or 8 high.

Thus you'd need about 60 to 72 horizontal pixels.

There are many sources of side stackable modules to build this up.

If you use a proportional font you will usually be able to fit your message
into fewer pixels, especially if you use mixed case instead of all CAPS.

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


{Original Message removed}

2000\11\13@204745 by Shahier Razik

picon face
Thanks eveeryone. Basically I need to make the final product about the size
of a badage. I have to be able to attach it to a bag, or a vest, or even the
back of bike. It has to be portable.
Thanks


{Quote hidden}

> > > > > > {Original Message removed}

2000\11\13@210122 by Bob Ammerman

picon face
At http://www.bgmicro.com

Part # LEDPD2435 - red, 4 character, 5x7 _small_ LED display, ASCII driven

Part # LEDPD2437 - green, 4 character, 5x7 _small_ LED display, ASCII driven

Datasheet:

http://www.bgmicro.com/pdf/pd24xx.pdf


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

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2000\11\13@214403 by Shahier Razik

picon face
Thanks for those parts BOb.

Could it be programmed using a PIC


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2000\11\13@215640 by Bob Ammerman

picon face
----- Original Message -----
From: Shahier Razik <EraseMEsrazik00spam@spam@HOTMAIL.COM>
To: <@spam@PICLISTspam_OUTspam.....MITVMA.MIT.EDU>
Sent: Monday, November 13, 2000 9:42 PM
Subject: Re: [pic] LED dot matix dsiplay


> Thanks for those parts BOb.
>
> Could it be programmed using a PIC

Easily!

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2000\11\13@215649 by Bob Ammerman

picon face
> At http://www.bgmicro.com
>
> Part # LEDPD2435 - red, 4 character, 5x7 _small_ LED display, ASCII driven
>
> Part # LEDPD2437 - green, 4 character, 5x7 _small_ LED display, ASCII
driven
>
> Datasheet:
>
> http://www.bgmicro.com/pdf/pd24xx.pdf
>

A little more detail:

Variable brightness under program control:
off, low, medium, high

$3.99 per 4 digit module.

These displays are 1" x .7" and contain 4  characters, on .25" centers. Each
character is 5x7 dots and .2" tall.

Pins are on 0.1" centers.

They can be stacked end to end to make any multiple of 4 characters.

Full upper and lower-case ascii.

Lamp test lights all 5x7x4 = 140 LEDs to 1/2 brightness @ about 42ma.

Normal operation at full brightness with 20 LEDs on in each character draws
about 140ma.

Straightforward interfacing will require 13 pins for the first 4 character
device, and one additional pin for each additional 4 characters.


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

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2000\11\13@223234 by Shahier Razik

picon face
Any ideas where I can find some helpful information (sample programs) on
programming LED displays uisng pic's


>From: Bob Ammerman <spamBeGoneRAMMERMANEraseMEspamPRODIGY.NET>
>Reply-To: pic microcontroller discussion list <PICLISTspamBeGonespamMITVMA.MIT.EDU>
>To: RemoveMEPICLIST@spam@spamspamBeGoneMITVMA.MIT.EDU
>Subject: Re: [pic] LED dot matix dsiplay
>Date: Mon, 13 Nov 2000 21:51:35 -0500
>
>{Original Message removed}

2000\11\13@233339 by Bob Ammerman

picon face
> Any ideas where I can find some helpful information (sample programs) on
> programming LED displays uisng pic's

Although I am sure there are samples for driving conventional multiplexed
LED displays, these displays are nothing like that.

In fact, from a programming point of view, these are much closer to an LCD
display.

Here is a little bit to get you started:

Assume you are using a 28 pin PIC. That'll give you enough I/O pins.

Assume we are using 4 4-digit displays.

Tie /RD high on all 4 LED devices

Connect CLK IO on all 4 devices together

Tie CLKSEL high on the first device, low on all the others

Tie all the RST's together and then to PORT A0 of the PIC.

Tie CE0 low on all 4 devices.

Connect PORT C to the data pins on all 4 LED devices.

Connect RB0 to to A0, RB1 to A1, RB2 to A2, RB3 to /WR on all 4 LED devices.

Connect RB4 to to CE1 on one device, RB5 to CE1 on a second device, RB6 to
CE1 on a third device, RB7 to CE1 on a fourth device.

Initialize PORT C to all outputs, with a value of 0.

Initialize PORT B to all outputs, with a value of B'00001000'.

Initialize PORT A bit 0 to be an output, with a value of B'0'


After powerup:

   bsf    PORTA,0            ; Allow LED devices to come out of reset


; The following code will clear all four devices, then write 'ABCD' on the
first device,

; (warning, untested code)

   MOVLW    B'11111000'        ; /WR is inactive,
                                                    ;CE1 set on all
devices,
                                                    ;address is 0
   MOVWF    PORTB

   MOVLW    B'10000011'        ; Clear command - full brightness mode
   MOVWF    PORTC

   BCF           PORTB,3             ; Generate /WR pulse (to all devices!)
   BSF           PORTB,3

   MOVLW    B'10001111'       ; /WR is inactive,
                                                   ; CE1 is set on first
device only,
                                                   ; address is 7 (leftmost
digit)

   MOVLW    'A'
   MOVWF    PORTC

   BCF           PORTB,3             ; Generate /WR pulse
   BSF           PORTB,3

   DECF          PORTB,F           ; Address 6 (2nd character)

   MOVLW    'B'
   MOVWF    PORTC

   BCF           PORTB,3             ; Generate /WR pulse
   BSF           PORTB,3

   DECF          PORTB,F           ; Address 5 (3rd character)

   MOVLW    'C'
   MOVWF    PORTC

   BCF           PORTB,3             ; Generate /WR pulse
   BSF           PORTB,3

   DECF        PORTB,F             ; Address 4 (4th character)

   MOVLW    'D'
   MOVWF    PORTC

   BCF           PORTB,3             ; Generate /WR pulse
   BSF           PORTB,3


hopefully that should be enough to get you started.

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

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2000\11\14@011755 by Shahier Razik

picon face
Thanks Bob for the code. But just a couple of beginner questions:

-what do you mean when you say device?
-what are the dimensions of the matrix we dealing with here?
-what exactly does that code you sent me accomplish?
Thank you

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2000\11\14@020302 by Bob Ammerman

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----- Original Message -----
From: Shahier Razik <srazik00EraseMEspam@spam@HOTMAIL.COM>
To: <RemoveMEPICLISTspamspamBeGoneMITVMA.MIT.EDU>
Sent: Tuesday, November 14, 2000 12:22 AM
Subject: Re: [pic] LED dot matix dsiplay


> Thanks Bob for the code. But just a couple of beginner questions:
>
> -what do you mean when you say device?

Each device is one 'chip' which contains 4 character positions, each of
which is a matrix of 5x7 LEDs.

> -what are the dimensions of the matrix we dealing with here?

Each character's 5x7 matrix is 0.2 inches high. They are placed on 0.25 in
centers.

The entire device is 1" x 0.7" .

> -what exactly does that code you sent me accomplish?

As mentioned in the comments:

"The following code will clear all four devices, then write 'ABCD' on the
first device,"


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

{Quote hidden}

on
> > > programming LED displays uisng pic's
> >
> >Although I am sure there are samples for driving conventional multiplexed
> >LED displays, these displays are nothing like that.
> >
> >In fact, from a programming point of view, these are much closer to an
LCD
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to
{Quote hidden}

the
{Quote hidden}

first
{Quote hidden}

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2000\11\14@030230 by Bill Westfield

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There's an interesting amount of variety in these sorts of devices.  The
$3.99 display Bob mentions accepts ascii.  B.G. Micro has another display,
an Agilent HDSP-2302 (ACS1076 $1.19) that is near the other end of the
spectrum, having only a 28 bit shift register for the 4 characters worth of
7 rows, and 5 column drivers.  The HCMS-291x I mentioned earlier is in
between, and has 40 bits of shift register for each character position, and
internal refresh logic.

BillW

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2000\11\14@031151 by Bob Ammerman

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BG Micro (http://www.bgmicro.com) has another option. Their ACS1076, which is a HP
HDSP-2303.

This is also a 4-digit 5x7 dot matrix 0.2" LED display. This one, however,
is much smaller. The 14-pin package is the same size as a DIP16. The
characters are 0.2" on center, and they are end-to-end stackable.

They are supposed to be quite bright (readable in direct sunlight!), but
they suck major current (as much as 500ma when fully lit)

The price is quite a bit lower: $1.19 for 1-9, $.89 at 10+.

These are no where near as smart as the others, however.

Basically, they contain a 28 bit shift register to define the current input
for the 7 rows of each of the four digits. There are 5 separate column
inputs that must be driven in sequence.

The basic operation:

1: Load the 28 bit shift register with the pixels for column 1 of each
character.

2: Enable the first column driver.

3: Delay

4: Disable the first column driver.

repeat steps 1 through 4 for the other 4 columns.

go back to step 1.

The PIC, in this case must continuously refresh (multiplex) the display.

A PWM drive can control the brightness.

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2000\11\14@112435 by Shahier Razik

picon face
Bob,

I checked out part #LEDPD2435 at bgmicro, but there was to preview of the
part. Let me get this straight. This part displays 4 characters at one time,
every character is 5x7 dots, .2" tall. The part contians 140 LEDs(5x7x4),
and it requires one PIC to program it.

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2000\11\14@152449 by Bob Ammerman

picon face
----- Original Message -----
From: Shahier Razik <srazik00spam@spam@HOTMAIL.COM>
To: <EraseMEPICLISTRemoveMEspamSTOPspamMITVMA.MIT.EDU>
Sent: Tuesday, November 14, 2000 11:24 AM
Subject: Re: [pic] LED dot matix dsiplay


> Bob,
>
> I checked out part #LEDPD2435 at bgmicro, but there was to preview of the
> part. Let me get this straight. This part displays 4 characters at one
time,
> every character is 5x7 dots, .2" tall. The part contians 140 LEDs(5x7x4),
> and it requires one PIC to program it.

Yes, yes, yes, yes, and yes.

The datasheet for this part is at:
http://ww.bgmicro.com/pdf/pd24xx.pdf

You can get a datasheet for the the other part (the smaller but dumber one)
at:
http://www.bgmicro.com/pdf/acs1076.pdf


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

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2000\11\15@003602 by Shahier Razik

picon face
Just wondering which model PIC should I use.

Thanks


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