# hello multiplexing....

Discussion in 'Programmer's Corner' started by RRITESH KAKKAR, Mar 9, 2015.

1. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
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Hello,
How to build these effects??

2. ### ErnieM AAC Fanatic!

Apr 24, 2011
7,308
1,568
It's just some LEDs on a board being rotated very fast.

Google "POV" or "persistence of vision."

3. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
2,831
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But i am not getting how to do this, I mean it is changing effect to in video.i think its not simple
as i have done in past work...

4. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
2,831
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Here are some video more of it!

5. ### John P Senior Member

Oct 14, 2008
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But surely it's not? Rotating I mean. Although the board is round, it's stationary, with just a pattern of lights rotating on it. The LEDs themselves seem to be the RGB tri-color kind. If the disk were rotating, there would just be one radial line of LEDs, and they'd be flashed at various points during the disk's rotation to create the design via POV. As it is though, the lights are arranged in a pattern that's clearly visible before the operator plugs the thing in.

The swastika is a little unnerving, but of course it doesn't have the same associations in Asia as it does in western countries.

As for "How to build these effects?" I'm not sure how to go about it. I'd start by laying out the pattern as little circles on a PC screen, then playing around with making them show different colors. You'd want to write routines like "expand pattern" and create patterns using trigonometric equations, then store the events (i.e. which color gets shown when) with timing for each LED. Since the patterns are usually symmetrical, you could save storage space by using the same timing for multiple LEDs.

One thing that suggests the whole thing is digital (if I counted it right) there are 32 radial lines on the disk, and each one contains 16 LEDs. But then, each LED would need 3 inputs for the colors, and you might want to give each color a pulse-width modulated drive to change the perceived brightness.

Last edited: Mar 11, 2015
6. ### ErnieM AAC Fanatic!

Apr 24, 2011
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Ah, it's a different impression if you actually play the video.

Still, it's just a bunch of LEDs on a board. The electronics is rather trivial, the artwork is the key sticky point.

My daughter is a great artist but she doesn't visit this site.

7. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
2,831
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the video say 16x48 led ..!!
so, it should be like scrolling display with effects!

8. ### John P Senior Member

Oct 14, 2008
1,609
216
Yes, that's what it is--similar to a rectangular scrolling display, but these are circular. The electronics would be pretty much the same. Maybe there's software you can download off the internet to create the patterns, so you could do the artistic part on your computer, and then you'd load it to the actual device. It seems as if anything that can possibly be done on a computer has been invented, and you can get it free!

RRITESH KAKKAR likes this.
9. ### vinnnie New Member

Jan 21, 2013
13
2
You need a lot of flip-flops integrated, I make something like this many years ago,but in that occasion I made a patrol police lights using various LEDs over a little bar.

10. ### MCU88 Member

Mar 12, 2015
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35
USD 20K ish is how you get one. BIG job.

Some rich dude on ecstasy (or similar) -- has done this. You're right, it is not simple.

Last edited: Mar 13, 2015
11. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
2,831
89
Sorry, i don't get you!

12. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
2,831
89
any which leds are these?

13. ### John P Senior Member

Oct 14, 2008
1,609
216
The LEDs seem to be something like this:
https://www.sparkfun.com/products/9264

You can get them much cheaper on eBay etc, which is a good thing because this project would use a lot of them.

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14. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
2,831
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Hi,
i seems nice, i want to know more i have seen some leds which can produce more color than RGB i.e 7 color combination of these after that digital led can have more color.

thanks

15. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
2,831
89
Hello,
what type of LED which automatically change color RB or RW or RBW they are some special sort of leds!

Oct 14, 2008
1,609
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17. ### Brevor Active Member

Apr 9, 2011
275
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If you look closely at the video, the LED's do not change color. From the center there are 4 amber LED's, 3 red, 3 green, 3 blue and 3 white. for a total of 16 in each line. the colors do not change.

18. ### John P Senior Member

Oct 14, 2008
1,609
216
Thanks for pointing that out, Brevor. I looked at the videos, but apparently I wasn't very observant. I came away saying "It has moving patterns. It has colors." And therefore, "Every color can be shown on every part of the display." That isn't true at all, and of course using ordinary LEDs makes the device a lot easier to build.

But Rritesh, the field is open for you to build a full-color version of one of these displays--nobody else is doing it!

19. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
2,831
89
Hello,
Thanks, you are right. i also viewed it just now!
pls tell how it is Rotating i mean working i am confused litle bit!

20. ### RRITESH KAKKAR Thread Starter Senior Member

Jun 29, 2010
2,831
89
hello again,
this is too cool video!

he says this, but i dnt get it!

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