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Author Topic: Building (or finding?) a special type of monitor  (Read 1129 times)

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Offline ComputerPsiTopic starter

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Building (or finding?) a special type of monitor
« on: January 12, 2010, 09:17:15 AM »
Hey, I'm looking for a special type of monitor. I hope you can help me out:
I need to be able to take a regular type of tv input.. Then output to a grid of LEDs. The LEDs light up and together form a picture based on the input. The LEDs should be regular one color bulbs. It would actually be better if I can replace these with regular incandescent lightbulbs.
Does anybody know the name of such a monitor.
I'm probably going to have to build this thing. I can get the grid of lightbulbs. What I need it a way to convert the standard input for a TV into individual grid electricity. Anybody know what device will allow me to do that?

Thank you.

Edit: Fixed spelling mistake. Thanks, GearMotion. ;)
« Last Edit: January 12, 2010, 09:35:20 AM by ComputerPsi »

Offline GearMotion

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Re: Building (or finding?) a special type of monitor
« Reply #1 on: January 12, 2010, 09:24:20 AM »
Indecent light bulbs. Those can be found in the red light district. :-P

Do you know how the TV signal works? I think you need to look at that first in order to have an appreciation of the complexity of your project.

http://en.wikipedia.org/wiki/NTSC
http://en.wikipedia.org/wiki/PAL

This has been done before, so there are examples on the web. It isn't a minor undertaking.
« Last Edit: January 12, 2010, 09:26:09 AM by GearMotion »

Offline ComputerPsiTopic starter

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Re: Building (or finding?) a special type of monitor
« Reply #2 on: January 12, 2010, 09:41:06 AM »
Indecent light bulbs. Those can be found in the red light district. :-P

Do you know how the TV signal works? I think you need to look at that first in order to have an appreciation of the complexity of your project.

http://en.wikipedia.org/wiki/NTSC
http://en.wikipedia.org/wiki/PAL

This has been done before, so there are examples on the web. It isn't a minor undertaking.


Thank you for your quick response GearMotion,
I do understand the complexity involved with the different television protocols present.
I do not intend on programming a chip to do this conversion. Instead I simply would like to purchase a chip that does this already. I assume all televisions have some type of chip that does a conversion from these NTSC, PAC protocols to something else. This is correct, no?
Well, is there a chip that can convert the signals to grid form like I noted? What is it called?

Thank you.

Offline GearMotion

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Re: Building (or finding?) a special type of monitor
« Reply #3 on: January 12, 2010, 10:15:00 AM »
Very unlikely you would find "a chip" that would do it all. You could start with this: http://www.national.com/mpf/LM/LM1881.html#Overview

Are you planning on duplicating all the lines/resolution? Likely not. So have you decided on the resolution? How will you downscale from NTSC/PAL resolution to the resolution of your array?

Offline ComputerPsiTopic starter

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Re: Building (or finding?) a special type of monitor
« Reply #4 on: January 12, 2010, 10:36:57 AM »
Are you planning on duplicating all the lines/resolution? Likely not. So have you decided on the resolution? How will you downscale from NTSC/PAL resolution to the resolution of your array?

In order to keep things simple, I plan to have the original video send in very low quality resolution. Hopefully low enough to match up with the resolution required. Don't know if that's possible though. Yes, I would be the one providing the low quality video.
Given the output of a high resolution grid, I can figure out how to make a low resolution grid out of it.


I looked at the LM1881 chip you posted. Looks like it has all the bells and whistles needed for inputting video signals. I don't know how to use this circuit though. The pages gives a lot of info about output of the chip...:
   Composite sync and vertical outputs
   Odd/even field output
   Burst gate/back porch output
   Edge triggered vertical output
   Default triggered vertical output for non-standard video signal (video games-home computers)

You know how to convert any of this into a simple analog grid?

Thanks,
ComputerPsi

Offline GearMotion

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Re: Building (or finding?) a special type of monitor
« Reply #5 on: January 12, 2010, 02:42:18 PM »
It won't matter if your video information is 200 by 200 or 5 by 5. If it is NTSC or PAL you will have a signal that is still in that format. You will need to DESIGN hardware to get to the resolution that you need.

Again: There is no single chip that will do this. And you are not going to be able to make this just by hooking a few simple things together with a couple of wires. You need to know what you are doing. If you can't fathom the LM1881, then you don't understand NTSC/PAL and don't understand the scope of what you are asking help with.

Offline nottoooily

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Re: Building (or finding?) a special type of monitor
« Reply #6 on: January 12, 2010, 10:59:13 PM »
If you want quick and easy, why not use a PC with a video capture card and some massive digital output adapter for all those individual signals?

How is the grid wired up? Does it already have switching/memory circuitry in it? If not then you've probably got a bigger challenge just getting anything at all displayed, and the details of whether it's TV or VGA or whatever are more trivial.

But don't be put off by how complicated NTSC/PAL seem. Remember the b/w versions of those standards were invented before they had chips!! You can ignore or filter out the color data which is where most of the complexity comes from. The odd/even fields are irrelevant to you because of the low resolution, just bang out each field as it comes. You can extract the horizontal and vertical sync pulses(with a chip) and use these to control some scanning circuit which switches between bulbs. Then just feed the whole analog signal through an appropriate amplifier/ADC and into the grid.

I'm imagining a counter which increments the row whenever it receives a horizontal sync pulse, and resets to the top when it gets a vertical sync. The output of this would directly switch the 'row' wires of the grid to, say ground. Then have a similar counter for columns, but this one's controlled by a timer so it scans across the screen at roughly the correct speed.





input for a TV into individual grid electricity. Anybody know what device will allow me to do that?

 


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