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### Topic: How to implement full color conceptually (Read 979 times)previous topic - next topic

#### Nonyaz

##### Mar 01, 2013, 02:34 pm
I'm not looking for specific components, I'm just trying to figure out the general process of home something gets displayed to an RGB LED matrix.

For example for a NxN single color matrix, the controller has to strobe line by line, so the brightness is cut by 10 right?

What about if you wanted a fractional color (half green, full red) for example, would you have to further sub strobe every line to "dim" colors?  Like maybe 10 cycles per line allowing for increments of 1/10th brightness for each color?

So now we're talking 10*n strobes to light the matrix with color.

So if my understanding on this is correct, now I'm curious about what frequencies of strobing are desired, whats the minimum, whats too slow?
And assuming I would be using shift registers, what kind of performance can I expect?

I'm basically trying to figure out a formula that works something like: Arduino can output x bit/s, then I can put in the matrix length and calculate with x levels of colors, how fast will the display update, ect, be able to make some performance predictions before I buy any components.

#### fungus

#1
##### Mar 01, 2013, 02:41 pm

I'm not looking for specific components, I'm just trying to figure out the general process of home something gets displayed to an RGB LED matrix.

For example for a NxN single color matrix, the controller has to strobe line by line, so the brightness is cut by 10 right?

Cut by 'N', yes.

What about if you wanted a fractional color (half green, full red) for example, would you have to further sub strobe every line to "dim" colors?  Like maybe 10 cycles per line allowing for increments of 1/10th brightness for each color?

If the time on each line is 1 millisecond (for example), the LED is switched on for a fraction of that millisecond.

The you move to the next line and repeat.
No, I don't answer questions sent in private messages (but I do accept thank-you notes...)

#### cmagagna

#2
##### Mar 01, 2013, 07:34 pm
Quote
What about if you wanted a fractional color (half green, full red) for example, would you have to further sub strobe every line to "dim" colors?  Like maybe 10 cycles per line allowing for increments of 1/10th brightness for each color?

It's a little more complicated than that, because your eyes perceive light logarithmically and not linearly, but yes that's the gist of it.

Instead of starting completely from scratch you might want to check out Elco Jacob's ShiftPWM (http://www.elcojacobs.com/shiftpwm/) and ShiftMatrixPWM (http://arduino.cc/forum/index.php/topic,66988.135.html) libraries.

Good luck!

#### Grumpy_Mike

#3
##### Mar 01, 2013, 08:17 pm
Quote
whats too slow?

The same LED has to be on 30 to 50 times a second to stop you seeing it as flickering.

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