On Wed, Mar 17, 2004 at 03:28:11PM +0200, Andre Miller wrote:
> I probably can, but doing it this way is more fun :-).
>
> I'm just going to lower the resistor values to get the correct brightness
> then (without exceeding the PIC ratings of course).

See my other post. I don't think you'll get there. Presuming a 1.7V drop
the absolute lowest resistance is 3.3/.024 -> 137 ohms. And that's pushing
the edge of the PIC I/O current drive capability. But the brightness will
still only seem to 137*4 -> 548 ohms. So it won't seem too bright.

My suggestion is to add a 7445 BCD to decimal driver will allow for 70 ma sink
through a 47 ohm resistor, though you can only light 1 segment at a time
instead of one display at a time.

BAJ.
>
>   _____
>
> Andr? Miller
>
> -----Original Message-----
> From: pic microcontroller discussion list [mailto:PICLIST@MITVMA.MIT.EDU] On
> Behalf Of bertrand.rozier@PRAGMATEC.NET
> Sent: 17 March 2004 02:41 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC:] Multiplexing seven segment displays, correct resistor
> values?
>
> Hi,
>
> I think there is not possiblity to improve that in soft.
> Could you confirm that you can not add a 7-segment drivers?
>
> BR
> Bertrand Rozier
> www.pragmatec.net
> PICOS18 Solutions
>
> Selon Andre Miller <andre.miller@BLUERIVER.CO.ZA>:
>
> > Hi,
> >
> > If I increase the 'on' time for a display, wont this then also
> > increase the 'off' time for the other displays, thereby negating the
> > benefit? I should be able to get this same effect by increasing the
> > prescaler on my timer interrupt that drives the displays. I tried
> > changing this and the lower frequency of updating didn't seem to make
> > a difference, except that it starts to flicker noticibly when its too low
> :-).
> >
> >   _____
> >
> > Andr? Miller
> >
> >
> > -----Original Message-----
> > From: pic microcontroller discussion list
> > [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of Spehro Pefhany
> > Sent: 17 March 2004 12:31 PM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: Re: [PIC:] Multiplexing seven segment displays, correct
> > resistor values?
> >
> > At 08:12 PM 3/17/2004 +1000, you wrote:
> >
> > >  If you have the time to spare, leave the leds on for a while, few
> > >mS, then switch to the next segment, and so on.
> > >  In other words, increase the "on" time compared to the off time.
> > >  Only works if your chip hasn't much else to do.
> >
> > He's using interrupts, so his program can walk and chew gum at the
> > same time, no problem. It shouldn't use more than a couple percent of
> > the processor throughput.
> >
> > Best regards,
> >
> > Spehro Pefhany --"it's the network..."            "The Journey is the
> > reward"
> > speff@interlog.com             Info for manufacturers:
> http://www.trexon.com
> > Embedded software/hardware/analog  Info for designers:
> > http://www.speff.com
> >
>
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