On 15 Sep 97 at 18:44, Martin R. Green wrote:

> In general, to get a multiplexed LED to display the same brightness as a
> direct driven LED you should overdrive each segment by the duty cycle of
> the scan.  That is, in our 8 LED example, if the LED display the brightness
> you need at 20mA per segment when driven directly, then you need to drive
> it at 160mA per segment to get the same brightness when multiplexing, since
> each LED is only on for 1/8th of the time.

I don't believe this is true.  The human eye seems to respond more to
the  PEAK of the intnesity.  Thus only a marginal decrease in
brightness is observed when the displays are mux'd at 20 ma in your
example.
--
Bob Fehrenbach  Wauwatosa, WI   bfehrenb@execpc.com