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Hello!
I am working on a project with an interface, and I want to use an RGB 8x8 multiplexed display that I have. The only problem is that a regular arduino is not fast enough to create a complex image on the display, since it is multiplexed.

The display has 32 pins: 8 for a row of green, 8 for a row of red, 8 for a row of blue, and 8 cathodes for the columns.

Is there any way I can control the display with 74HC595N shift registers (I have just enough of them) or any other chips, or maybe even an arduino designed to operate LEDs?

Thanks in advance  smiley
-Dylan
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The only problem is that a regular arduino is not fast enough to create a complex image on the display, since it is multiplexed.
Using shift resisters only slow things down so it will not increase the speed.

What refresh rate do you want?
How have you got it wired?
What code are you using!
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Yes it is.

You can use 74HC595. But you also need a "buffer" like ULN2003 driver with a limiting resistor for each led's or use transistor like 2N3904 or stronger. Th Arduino is fast enough to do this project.  I don't know how the display is connected ( inside or outside ), but you MUST use limiting resistors and transistors and base resistor to control each LED color and the cathode. I also see that you will need 4 74HC596, 8 NPN + base resistors for the cathodes, 24 PNP + limiting led resistor + base resistors to control each color led. Connect properly and program properly according to the hardware, you will be sucessfull doing this project.

Here a pictures of my Matrix setup. And a schematic setup of the Matricx I am using. In your case, it will be different. I hope it will give you an idea.  

Oh.. one thing... To turn On a NPN transistor, a 1 is needed. To turn on a PNP transistor, a 0 is needed. Be aware of that little fact.      


* matrix.jpg (161.53 KB, 1024x768 - viewed 55 times.)

* Matrixcellv2.jpg (76.88 KB, 1024x700 - viewed 69 times.)
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The only problem is that a regular arduino is not fast enough to create a complex image on the display, since it is multiplexed.

Then you're doing it wrong. 8x8 RGB is only 192 LEDs. Many people have made much larger displays than that with the Arduino, to wit:

http://www.youtube.com/results?search_query=arduino+rgb+led+matrix&oq=arduino+rgb+led+matrix&aq=f&aqi=&aql=&gs_sm=3&gs_upl=1048l4445l0l4585l22l22l0l14l14l0l174l628l3.3l6l0

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Is there any way I can control the display with 74HC595N shift registers

Yes.

http://www.elcojacobs.com/shiftpwm/

and

http://arduino.cc/forum/index.php/topic,66988.0.html

As Techone says, you will need limiting resistors (so you don't burn out the LEDs) and transistors on either the rows or columns (so you don't burn out the shift register's pins).

Good luck!
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Thanks a lot for all the replies!

I think that I will approach this either with the ShiftPWM library and a setup like Techone's, or  this shield that I just foundhttp://iteadstudio.com/store/index.php?main_page=product_info&cPath=18&products_id=312 . Now I have to decide whether to take the more fun, but not as practical route, or the easy and practical route. smiley-razz

You guys were really helpful, thanks again!
-Dylan

Edit: For now, I will go practical, but I'll probably try to make a larger display some time in the future.  smiley
« Last Edit: February 22, 2012, 08:37:13 pm by FutureInventions » Logged

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