Hi seeedstudio,
juilenb is not using an LED matrix but separate LEDs, data here:-
- 64 RGB leds ( http://www.sparkfun.com/commerce/product_info.php?products_id=105 )
they will be quite different.
I did talk about multiplexing and duty cycles earlier in the thread.
You should really not use LEDs without resistors as you are then relying on the driving circuits to go into current limit and this will most likely stress them. It will work, but not for very long or reliably. That is why you say the 5V was too bright, much longer and they probably would have gone out.
For the current calculation, you should divide it by the frequency if dynamic scan
It is not the scan frequency that matters at all, it is the ratio of on to off time. This should be expressed as a percentage and used to calculate the average current.
I was making the point that this not only cuts down the current but also cut down the brightness and so you might have to increase the current even further to componsate.
Measuring the current of a multiplexing display is tricky because you have a rapidly varying current and most current meters will not give you an accurate measure of this. At best a moving coil meter will show the average current not the peak current which is what you want in this situation.
The best way to measure the current is by looking at the voltage across an in line resistor, then you can see exactly what is happening.