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Discussion Groups | Comp.Arch.Embedded | How to build your own LED TV-like color displays?

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How to build your own LED TV-like color displays? - 2005-12-28 02:47:00

There are some companies manufacturing large LED based TV-like, color 
display units.
http://www.monstavision.com/
http://www.polycomp.co.uk/led-display-video-&-graphic.htm
http://www.daktronics.com/video_prod/dak_video_products.cfm

http://www.gizmag.com.au/go/4880/
http://engadget.com/2005/10/08/daktronics-to-build-worlds-largest-hd-led-display/

Electronics is an amateur hobby for me and I would like to investigate (and 
eventually build) the design issues of LED based TV-Like color display 
units.
As a starting point I would see the following grouping of issues;
    1.) Mechanical design and manufacture of the modular LED panels
    2.) Automatic LED adressing protocol (this will initialize individual 
LED panels as well as individual LED when panels are connected with each 
other to form large 2D matrix)
    3.) Selecting/sourcing bright and low-cost LED with almost identical 
specs.
    4.) Digitising video into NxM color pixels (N, and M are number of 
pixels in Row and Column)
    5.) Sending the digitized image to indivually addressed LED panels
    6.) Each LED panel should be intelligent to receive part of the 
digitized video data corresponding to its own spatial position
    7.) Scanning LEDs according to received pixel data.

Do you have any idea, information, design, URL etc. about above mentioned 
and/or any other related issue to share?

Thanks.

Nicky 



Re: How to build your own LED TV-like color displays? - MC - 2005-12-28 03:16:00

Nicky wrote:

> There are some companies manufacturing large LED based TV-like, color 
> display units.
> http://www.monstavision.com/
> http://www.polycomp.co.uk/led-display-video-&-graphic.htm
> http://www.daktronics.com/video_prod/dak_video_products.cfm
> 
> http://www.gizmag.com.au/go/4880/
> http://engadget.com/2005/10/08/daktronics-to-build-worlds-largest-hd-led-display/
> 
> Electronics is an amateur hobby for me and I would like to investigate (and 
> eventually build) the design issues of LED based TV-Like color display 
> units.
> As a starting point I would see the following grouping of issues;
>     1.) Mechanical design and manufacture of the modular LED panels
>     2.) Automatic LED adressing protocol (this will initialize individual 
> LED panels as well as individual LED when panels are connected with each 
> other to form large 2D matrix)
>     3.) Selecting/sourcing bright and low-cost LED with almost identical 
> specs.
>     4.) Digitising video into NxM color pixels (N, and M are number of 
> pixels in Row and Column)
>     5.) Sending the digitized image to indivually addressed LED panels
>     6.) Each LED panel should be intelligent to receive part of the 
> digitized video data corresponding to its own spatial position
>     7.) Scanning LEDs according to received pixel data.
> 
> Do you have any idea, information, design, URL etc. about above mentioned 
> and/or any other related issue to share?

Structural, comms, bandwidth and power hassles will excalate
at an x by y rate. (at least).

Consider reliabilty, repair, 'fail gracefully', self-test
and fault-diagnosis issues.

Add in variations in LED colour and luminance with age
and manufacturer and manufactured date.

Not a trivial or cheap project beyond around 150 x 40 pixles.

Re: How to build your own LED TV-like color displays? - David L. Jones - 2005-12-28 03:39:00

MC wrote:
> Nicky wrote:
>
> > There are some companies manufacturing large LED based TV-like, color
> > display units.
> > http://www.monstavision.com/
> > http://www.polycomp.co.uk/led-display-video-&-graphic.htm
> > http://www.daktronics.com/video_prod/dak_video_products.cfm
> >
> > http://www.gizmag.com.au/go/4880/
> > http://engadget.com/2005/10/08/daktronics-to-build-worlds-largest-hd-led-display/
> >
> > Electronics is an amateur hobby for me and I would like to investigate (and
> > eventually build) the design issues of LED based TV-Like color display
> > units.
> > As a starting point I would see the following grouping of issues;
> >     1.) Mechanical design and manufacture of the modular LED panels
> >     2.) Automatic LED adressing protocol (this will initialize individual
> > LED panels as well as individual LED when panels are connected with each
> > other to form large 2D matrix)
> >     3.) Selecting/sourcing bright and low-cost LED with almost identical
> > specs.
> >     4.) Digitising video into NxM color pixels (N, and M are number of
> > pixels in Row and Column)
> >     5.) Sending the digitized image to indivually addressed LED panels
> >     6.) Each LED panel should be intelligent to receive part of the
> > digitized video data corresponding to its own spatial position
> >     7.) Scanning LEDs according to received pixel data.
> >
> > Do you have any idea, information, design, URL etc. about above mentioned
> > and/or any other related issue to share?
>
> Structural, comms, bandwidth and power hassles will excalate
> at an x by y rate. (at least).
>
> Consider reliabilty, repair, 'fail gracefully', self-test
> and fault-diagnosis issues.
>
> Add in variations in LED colour and luminance with age
> and manufacturer and manufactured date.
>
> Not a trivial or cheap project beyond around 150 x 40 pixles.

Definitely.

But wouldn't a 720 x 576 panel be one heck of a project!

Dave :)


Re: How to build your own LED TV-like color displays? - 2005-12-28 05:34:00

On Wednesday, in article
     <43b24292$0$9286$a...@news.optusnet.com.au> Nicky wrote:

>There are some companies manufacturing large LED based TV-like, color 
>display units.
>http://www.monstavision.com/
>http://www.polycomp.co.uk/led-display-video-&-graphic.htm
>http://www.daktronics.com/video_prod/dak_video_products.cfm

These are large displays that draw a lot of power (some modules are specced
at 0.5KW and higher per module)!
>
>http://www.gizmag.com.au/go/4880/
>http://engadget.com/2005/10/08/daktronics-to-build-worlds-largest-hd-led-display/

That one is going to need special cameras and other gizmos to drive it
as well as possibly its own power station!

>Electronics is an amateur hobby for me and I would like to investigate (and 
>eventually build) the design issues of LED based TV-Like color display 
>units.

Well that all depends on what you are used to. The bits described above are
LARGE systems with teams of people working on different parts.

>As a starting point I would see the following grouping of issues;
>    1.) Mechanical design and manufacture of the modular LED panels
>    2.) Automatic LED adressing protocol (this will initialize individual 
>LED panels as well as individual LED when panels are connected with each 
>other to form large 2D matrix)

Not unsurmountable, if you use a scalable design methodology. But will
probably require lots of LED drivers to keep LEDs 'ON' until a new value
appears, CRT and LCD have a persistence that keeps the 'dot' bright for
longer than the sweep of 'addressing' each 'dot'.

Please also consider what resolution display you want to make and then
total up the power involved in doing this and how you are going to drive
the POWER.

If all LEDs permanently left ON for QVGA resolution and various LED
currents

        Total LEDs      320 x 240       = 76800

        @ 10mA per LED  0.01 * 76800    = 768A  (yes AMPS)

        @ 5mA per LED   0.05 * 76800    = 384A

        One line of LEDs ON at a time   = 320 * 0.01 = 3.2A

Sorting out what POWER distribution and LED control is a CRUCIAL part of
this sort of design. These figures are true even if they are ALL turned
on at the same time for a short period of time, just the same current
is seen for a shorter period of time repeatedly.

How to turn on LEDs, for how long and how many at the same time has effects
on power and how you see the image (too dim, pulsing, beat frequencies).
Line at a time can cause vertical beat frequency 'cycling' through the
picture, groups at a time on can cause bands or other distortions, where
as single LED at a time on

>    3.) Selecting/sourcing bright and low-cost LED with almost identical 
>specs.

Being sure you can get colour balance across the 'screen' will be the main
issue there, where by you see the same level and mix of colours for the
same colour at all points on the screen (within a _small_ tolerance) as
the eye will pick out the differences.

>    4.) Digitising video into NxM color pixels (N, and M are number of 
>pixels in Row and Column)

Your real problems are not so much the digitising, but synchronising and
scaling/cropping when you have different number of LEDs (pixels) compared
to input resolution and how to handle it.
Not forgetting if you are taking PAL or NTSC video, you have the
de-interlacing to deal with.

>    5.) Sending the digitized image to indivually addressed LED panels

The real crucial issue is anything beyond 1bit depth per colour (R, G and B)
is a complicated distribution

        analog - switching and distribution without signal loss across
                the dispaly modules

        digital - transferring all the digital levels, between the modules
                (lots of wires or lots of higher speed serial transmission)

>    6.) Each LED panel should be intelligent to receive part of the 
>digitized video data corresponding to its own spatial position

Which requires some form of intelligent controller that parcels out the
data (or provides clocking signals to say module start/end).

>    7.) Scanning LEDs according to received pixel data.

Shift register controls (chips or PLD) are probably the easiest method
for scan control, and cascadeable between modules. See also above about
power and duty cycle of LEDs.

>Do you have any idea, information, design, URL etc. about above mentioned 
>and/or any other related issue to share?

Look at some of the Disco Dance floor designs for how people have done
projects with modular LED panels if nothing else for driving tehniques.
You will need a higher density of LEDs.

Such as

        <http://web.mit.edu/storborg/ddf/>
        <http://betterthaneveryone.com/>
        <http://www.biketiresdirect.com/ddforders.html>

>Thanks.
>
>Nicky 
>
>
>

-- 
Paul Carpenter          | p...@pcserviceselectronics.co.uk
<http://www.pcserviceselectronics.co.uk/>    PC Services
<http://www.gnuh8.org.uk/>              GNU H8 & mailing list info
<http://www.badweb.org.uk/>             For those web sites you hate


Re: How to build your own LED TV-like color displays? - Anton Erasmus - 2005-12-28 06:22:00

On Wed, 28 Dec 2005 18:47:54 +1100, <Nicky> wrote:

>There are some companies manufacturing large LED based TV-like, color 
>display units.
>http://www.monstavision.com/
>http://www.polycomp.co.uk/led-display-video-&-graphic.htm
>http://www.daktronics.com/video_prod/dak_video_products.cfm
>
>http://www.gizmag.com.au/go/4880/
>http://engadget.com/2005/10/08/daktronics-to-build-worlds-largest-hd-led-display/
>
>Electronics is an amateur hobby for me and I would like to investigate (and 
>eventually build) the design issues of LED based TV-Like color display 
>units.
>As a starting point I would see the following grouping of issues;
>    1.) Mechanical design and manufacture of the modular LED panels
>    2.) Automatic LED adressing protocol (this will initialize individual 
>LED panels as well as individual LED when panels are connected with each 
>other to form large 2D matrix)
>    3.) Selecting/sourcing bright and low-cost LED with almost identical 
>specs.
>    4.) Digitising video into NxM color pixels (N, and M are number of 
>pixels in Row and Column)
>    5.) Sending the digitized image to indivually addressed LED panels
>    6.) Each LED panel should be intelligent to receive part of the 
>digitized video data corresponding to its own spatial position
>    7.) Scanning LEDs according to received pixel data.
>
>Do you have any idea, information, design, URL etc. about above mentioned 
>and/or any other related issue to share?
>

You are probably going to be overrun with the new OLED/PLED
Technology. Samsung has demonstrated a 40" OLED Display panel.
The resolution is 1280x800, which is just over 3 million LEDs.
Stacking smaller panels, in stead of individual LEDs probably makes
more sense for future products. 

http://www.samsung.com/PressCenter/PressRelease/PressRelease.asp?seq 050929_0000194163

Regards
  Anton Erasmus

Re: How to build your own LED TV-like color displays? - MC - 2005-12-28 20:15:00

>>
>>Not a trivial or cheap project beyond around 150 x 40 pixles.
> 
> Definitely.
> 
> But wouldn't a 720 x 576 panel be one heck of a project!

hmmm, that'll need around 4m x 3m of surface area if
you use 3mm leds.
Awkward for personal viewing, but if you don't close
the curtains then I'm sure that the neighbours will
appreciate it <g>

I'll let you pay for the 240 Amps (peak) to run it.

And 3x 414720 high luminance Leds at (say) $0.10 each
comes to around $124k.
oh, you don't want a visible-in-daylight display ?,
fine, we'll use ordinary cheap Leds at $0.01 each
to reduce the price of the visible-bits to around $12k.

Re: How to build your own LED TV-like color displays? - Mark Haase - 2005-12-28 23:45:00

In article <dovdbp$o4k$1...@news-01.bur.connect.com.au>,
 MC <M...@nonexistent.place> wrote:

> I'll let you pay for the 240 Amps (peak) to run it.
> 
> And 3x 414720 high luminance Leds at (say) $0.10 each
> comes to around $124k.
> oh, you don't want a visible-in-daylight display ?,
> fine, we'll use ordinary cheap Leds at $0.01 each
> to reduce the price of the visible-bits to around $12k.

Where on earth would you source 240 amps from? I don't have such a 
circuit in my house.

Also, the time to fabricate, by hand, would be incalculable.

My question is can the LEDs be operated in various intensities, or is it 
only full-off/full-on? If its it the latter, how do you produce gray? If 
its the former, how to you duty-cycle modulate millions of LEDs?

-- 
|\/|  /|  |2  |<
mehaase(at)gmail(dot)com

Re: How to build your own LED TV-like color displays? - Mark Borgerson - 2005-12-29 00:16:00

In article <m...@news1.east.earthlink.net>, 
m...@gmail.com says...
> In article <dovdbp$o4k$1...@news-01.bur.connect.com.au>,
>  MC <M...@nonexistent.place> wrote:
> 
> > I'll let you pay for the 240 Amps (peak) to run it.
> > 
> > And 3x 414720 high luminance Leds at (say) $0.10 each
> > comes to around $124k.
> > oh, you don't want a visible-in-daylight display ?,
> > fine, we'll use ordinary cheap Leds at $0.01 each
> > to reduce the price of the visible-bits to around $12k.
> 
> Where on earth would you source 240 amps from? I don't have such a 
> circuit in my house.

240 amps at ~3V for the LEDs is only about 8 Amps at 110V.   The power
supply shouldn't be that tough to build.
> 
> Also, the time to fabricate, by hand, would be incalculable.

Not really---at least if you have a decent computer and Excel.
> 
> My question is can the LEDs be operated in various intensities, or is it 
> only full-off/full-on? If its it the latter, how do you produce gray? If 
> its the former, how to you duty-cycle modulate millions of LEDs?
> 
I suspect that it would be similar to the fashion in which you modulate 
millions of pixels in an LCD display.   Kodak is making OLED displays
with 521x218 resolution now---this should just be a step up in size!  
;-)

http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=2/782/1473/1481/1486/1495&pq-locale=en_US

Mark Borgerson



Re: How to build your own LED TV-like color displays? - Grant Edwards - 2005-12-29 00:20:00

On 2005-12-29, Mark Haase <m...@gmail.com> wrote:

> Where on earth would you source 240 amps from? I don't have such a 
> circuit in my house.

I think that was the point.

> Also, the time to fabricate, by hand, would be incalculable.

Long, yes. Incalculable, probably not.

> My question is can the LEDs be operated in various intensities, or is it
> only full-off/full-on?

Usually the latter.  You can operate them at variable intensity
by varying the amount of current, but that's difficult.  To
acheive "gray" you usually use pulse-width-modulation to vary
the duty cycle.

> If its it the latter, how do you produce gray?

Pulse width modulation.

> If its the former, how to you duty-cycle modulate millions of
> LEDs?

Good question.

-- 
Grant Edwards
g...@visi.com

Re: How to build your own LED TV-like color displays? - MC - 2005-12-29 00:32:00

Mark Haase wrote:

> In article <dovdbp$o4k$1...@news-01.bur.connect.com.au>,
>  MC <M...@nonexistent.place> wrote:
> 
> 
>>I'll let you pay for the 240 Amps (peak) to run it.
>>
>>And 3x 414720 high luminance Leds at (say) $0.10 each
>>comes to around $124k.
>>oh, you don't want a visible-in-daylight display ?,
>>fine, we'll use ordinary cheap Leds at $0.01 each
>>to reduce the price of the visible-bits to around $12k.
> 
> 
> Where on earth would you source 240 amps from? I don't have such a 
> circuit in my house.

This current would be at around the 3 (or so) volt level, so
you'll only need about 750W (peak) from the mains.

> Also, the time to fabricate, by hand, would be incalculable.

Not if you get it hand-assembled in China !
I once spend half a day populating and soldering a 256 Led panel. yetch.

> My question is can the LEDs be operated in various intensities, or is it 
> only full-off/full-on? If its it the latter, how do you produce gray? If 
> its the former, how to you duty-cycle modulate millions of LEDs?

To create colour, you need different intensities of the primary colours,
and the usual technique is to use pulse-width-modulation (PWM) because
it reduces power consumption and heat.
You'll also need colour correction of some sort because the Leds
you buy now will have different characteristics from the
ones you buy in 6 months time. (even if it's the same part number).
You can reduce this to some extent by buying a particular 'bin'
of tested and sorted devices, but the price then goes up a lot.

As to how to control millions of LEDs.., that I'll leave as an
exercise for you <g>,
but bear in mind that control and communication techniques which
work ok for a small number of pixels tend not to scale-up very
well when the numbers get into the realm of thousands of pixels.

Most sign manufacturers organise pixels in groups that can be
easily manufactured, installed and repaired as one entity.
eg. vertical strips of 2 x 16 pixels or 8 x 8 pixel panels,
etc etc etc.

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