It sounds to me like you're running out of voltage.  Each LED
 (I'm assuming RED) drops about 1.2 volts at a current of about
 20 mA.  You have 5 in series for a total of 6V (1.2x5=6).  So,
 you'll have to have a higher voltage supply, or use fewer LED's
 per segment.  You could try 4 per segment for 4.8 volts, but
 that too will be close.

                                       Regards,

                                         Jim



On Wed, 23 February 2000, Omar Martinez wrote:

>
> Gentlemen:
>
> I'm making a device that show the time and temperature with a 16F84 and it
> work fine with led display of 1" in size, so when I try to use led displays
> of 4" size, the segments don't
> turn on...
> In the led display spec's, I saw the connection diagram and it's made with 5
> leds connected in serial mode for each segment (common cathode), except for
> the decimal point that have only one.
> All the device is powered with standard +5 Volt regulator, the segments are
> driving directly from PortB thru limiting resistors and each display is turn
> on every 3 mSec. via transistor from portA.
>
> Can anyone please help me with this problem?? I will appreciate it!!!
>
> Thanks & excuse for my english....
>
> Omar

jim@jpes.com