DIY RGB LED Bars and the TLC5940

HI all,

I need a little advice re the schematic i am working on. I would like to set up multiple RGB bars to be controlled from my Arduino. After playing around with the TLC5940, i think this will be the chip i would like to use for my project but powering everything is something i am struggling to understand. After some research in the forum here and came across this topichttp://arduino.cc/forum/index.php/topic,78064.0.html.

Member CrossRoads posted some schematics for driving multiple leds half way down the post so i set to work coming up with the schematic posted here and am hoping i’m on the right track, but of course wanted to get the wisdom of the members here to see if i’m barking up the wrong tree.

I would like to use 14 bars overall so will need 3 TLC5940’s (which i have) for all the channels needed to control the r, g and b of each bar.

So really my question is “Is this gonna work???”.

Thanks for your time.

My Schematic is attached

Due to the way the chip works when you invert the output like this you will never be able to turn the LEDs completely off if you invert the signal. This is because the missing clock period in full brightness actually gets noticed when it is an on clock period.

Hi GrumpyMike,

Thanks for the response, I shall go away and investigate a little further. Do you think it is feasable to run 14 bars from 5V 1000ma power supply or am I gonna need something a bit beefier?

Update As I was Searching i found this - Schematic attached.

Hooked this up to my arduino and seemed to work but will test with the TLC5940 later(needed to go to bed!!!)

I would put a 10K from the base of the PNP to the +12V. However if you are thinking of using the outputs from the TLC5940 to drive this then still inverts the signal and so you have the same problem as before.

Hi again,

Thanks for the info, i will go away and research some more.

Cheers.