I've just started charlieplexing and may need to head to the store tomorrow to pick up breadboard parts...
Can anyone see any issues with the way I laid this out?
Thanks!
Edit: The reason there are 2 separate charlieplexes is that one goes on each side of a board. This means 4RGB LEDs on top, and 4 on the bottom.
Where to place the resistors (see attachment)
http://rweather.github.io/arduinolibs/charlieplexeg.png
Value will have to be experimented for, mixing R's, G's, B's this way.
Maybe 100 ohms each.
I will try them right now, thanks!
Red Green Blue! Thanks!
If i can suggest a couple of tips...
Remember that with the resistors placed as suggested by RP, the current flowing through any led passes through two of them. So if they are 100R, then you have series resistors equivalent to 200R and half the current you might have expected. In this example the current will be around 10mA, not the 20mA you might have been expecting.
Also, the forward voltage of the red leds in an rgb led is considerably lower than the green and blue leds. If you don't correct for this, when you try to mix colours or make white, they will all be a little dominated by red, for example white will come out somewhat pink. To correct for this, you could put an extra low value series resistor, around 50R, in series with each of the red leds.
Paul
OK, you put the resistors only on the anode side of the LEDs, presuming you are going to drive a cathode low and select a number of anodes to activate.
You may however need buffers to carry the common current, in which case the buffer transistors need to drive common anodes, and the resistors to the cathodes, a number of which may be driven together according to the pattern at that multiplex phase thus:
And note a further benefit of the buffer transistors - their collectors go to the unregulated supply to the Arduino, not to its 5 V supply (unless this is an external 5 V regulated supply feeding the Arduino), so there is negligible current drawn from the Arduino regulator.
