Hi Colin: There's an even easier way that takes only 3 pins for any number of 7-segment LEDs. And that's to use the Allegro 6276 STATIC driver chip. It has built in current regulation so you can make the LEDs as bright as you have power supply, unlike muxing where you get less light output per watt of DC input. Each 6276 will drive 2 each 7-segment displays or one each 14/16-Segment alpha numeric LED. See: Have Fun, Brooke Clarke, N6GCE http://www.PRC68.com >Date: Tue, 2 Sep 2003 17:04:11 -0600 >From: Colin Constant >Subject: Re: [PIC]: 4 7-seg displays > >What's a good transistor to use to drive Common Cathode 7 segment displays? > >TIA >Colin > > > >> I have a question regarding the driving of 4 7-seg displays. Originally, >>I did >>this the easy no-brainer way, which was basically use 2 whole ports >>connected >>to 4 7-seg decoders, and then to the displays... but this, obviously, takes >>a >>lot of IO pins. I then went on the piclist site to see if there's a better >>way, >>and came across this method: >> >>http://www.piclist.com/techref/io/led/8x7s8pin.htm >> >>It seems like a great idea (although harder to code), but first off, does >>this >>method have to be done with common anode (as is described), or can I >>basically >>reverse it to use a common cathode display? I don't see any problem with >>doing >>so, I just figured that I might be missing something though. Second, are >>there >>any better methods that are commonly used? >> >>Thank you all!! >> >>Jai >> > > > > -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu