A quick update on an old thread

Ten digits from 6 pins

My main gain on this design is the very simple programing
and wiring

The first four pins of a PIC port go to a 74LS47
BCD to seven seg driver, the seven outputs are connected in parallel
to all the segments.
The next two pins go to the reset and count pins of a 4017(decade
counter
with 10 decoded outputs)
the ten decoded outputs connect direct to the bases of ten npn emitter
followers, all collectors +5V, emitters connect to the common anode
of each digit

Parts 1 x PIC + ceramic res, 1 x 7447, 1 x 4017,
10 x transistors (I used 2SC1740) npn,
no resistors !

Driving is simple
;first digit
logical high on the reset line     ; reset to 0
then output your number in binary to the port (top 4 bits=0 which will
pull
the reset back down)
wait 2msecs
;second and all following digits
logical high on count             ; advance one digit
then out put your number in binary to the port (top 4 bits=0 which will
pull
the count line down)
wait 2msecs
logical high on count             ; advance another digit
.................; till all ten done

I have it sitting in front of me, with a refresh rate of 50hz I can
see no flicker, it's drawing around 150ma and it is bright

--
Peter Cousens
email: peter@cousens.her.forthnet.gr  phone: + 3081 324450, 380534
snailmail:  Folia, Agia Fotini, Karteros, Heraklion  Crete, Greece.