And don't forget that one can increase the number of digits by daisy
chaining the
4017's.  Of course one will have to make sure to maintain the 50+ Hz
refresh rate.

Peter Cousens wrote:

> 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.