You have a total of 60 individual LED's to deal with. I would be tempted to arrange them in a 6 x 10 array and multiplex them. I'd drive the ten rows with transistors driven by an 74HC42 decade decoder. The six columns would then be directly driven, using software PWM, from PIC pins. Bob Ammerman ----- Original Message ----- From: "Tony Harris" To: Sent: Sunday, December 14, 2003 6:18 PM Subject: [EE:] Driving multiple RGB LED's...? > Hi all, > > First off - this is NOT an assigment, this is an experiment of my own =) > > I find myself wanting to experiment with something but a little lost. > > I want to drive 20 RGB LED's - each LED has 4 leads, 1 r, 1 g, 1 b, 1 common > cathode. > > My desire is to drive this array of 20 led's with a small pic (preferrably a > 28 pin pic) where I can have a few pins left over to communicate with a host > computer so I can set what I want each LED to produce in color. > > I was originally thinking of dpots controlling transistors or fets, but the > chip count became too big - at 2 dpots /ic, and needing 60 controlled led's, > (20x3) that's 30 dpot ic's, way too many. > > I then thought of some sort of pwm to control led brightness for given > colors - but that would require 2 pics - even if I used a larger pic to do > it, I don't have the tools to program one of those 68 pin pics. > > I was then thinking of some sort of switching arrangement where I'm only > controlling say 2 led's at a time for pwm and shifting to the next bank > every .5mS to make sure none of them appeared too dim. > > So far, the last option has been the best option I could imagine at this > moment in time, but I am not sure it is the best option - does anyone have > any ideas/suggestions? > > -Tony > > -- > http://www.piclist.com hint: The list server can filter out subtopics > (like ads or off topics) for you. See http://www.piclist.com/#topics > -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics