turning on red seriously depletes or turns off output from all other lights

[Joel]

Hi.  I am using a lightuino 5 and have run into an issue where sinking one pin with a lower voltage led depletes the currents on other pins with other colors.  I would like to know why this is happening and what I can do to prevent it. 

I made an experimental array of 9 sets of RGB  and UV LEDs.  all 9 sets share a common source V from a source pin on the lightuino and each set has 4 drains, (one per color), thus 32 drains pins total.     These will eventually go into a matrix 14 audio reactive light pipes for a psychedelic organ.  When i run AllOn().  The array only out put red lights.   Upon fiddling with the trimmers I was able to barely get some of the other lights to come on but not the UVs.  However still my source voltages would not go above 3.7 V (with no lights plugged in).    When I unplug everything but the UV lights, the UV lights are on,  but when i plug any of the RGB pins in for any of the lights all of the UV lights go out.  similarly when i unplug all but blue lights, they shine bright, but when I plug in any of the red lights any and all of the blue lights dim dramatically.  there is a much smaller effect with green.   

I imagine this has something to do with the various forward voltages of the LEDs:  listed specs of leds are :  red is 2v, green is 3.2V, blue is 3.2V, (25mA max), uv is 3.0-3.4 (24mA max).   I am using the 5 wall wart that came with the lightuino.   I am hooked it up with an extra LED of each color in parallel on each set, so for example that set 1 has 2 RGB LEDs, and 2 UV leds.  with the cathodes of the same color are hooked up to the same sink pin, and all anodes from all sets and colors are hooked up to the same source pin.    I have tried having more than one souce pins driving the leds simultaneously with the same results.  

Also I just discovered that this does not happen if I use the 5V supply instead of a source pin.    But i will need to use these sources pins to drive my matrix.

So how can I fix this?  And how do I make my source pins higher than 3.7 volts?

Many thanks,

Joel    

[Joel Horne]

Also. I thought it may have been some short circuit in the wiring of
my array. So i hooked it up on a breadboard with one simplified set
(one RGB LED, one UV LED) with common source. I then turned on only 1
source and 4 sinks to drive the them, but have the same result: only the
red led being visible until i unplug it then only the blue and green and
when i unplug them then finally the UV light comes on.

[Andrew Stone]

It could be that your center pot needs adjustment.  But most likely the 5v supply is too low when you go through the regulator, the source and sink drivers and the LED.  You can try a higher voltage supply... 7-12v should work -- test the voltage at the IDE "LED" power pins (circled on the board) and turn the center pot until its around 5-6v.  Also the 5v wall wart you bought from me is "regulated", so it can directly power electronics.  So can connect Vin directly to the "LED" power pin (again the circled one).  This will bypass the onboard voltage regulator saving you about 1v which should be enough to drive the other color LEDs...

Sorry about this... I should document this issue with the 5v supply.

Cheers!
Andrew

[Joel]

Thanks again Andrew!   I am now using a +12V from computer power supply and I adjusted the center trimmer to 5V and  lights all seem to be working as they should now. 

Cheers! 

Joel