On Fri, Sep 12, 2003 at 02:59:00PM -0500, Patrick Richards wrote:
> This brings up the questions of how long an individual segment has to be
> on, how quickly to refresh the display, and by how much you can
> overpower each segment.  With 4 displays of 7 segments each, that is 4 *
> 7 = 28 LEDs to light in turn.

Yes.

>
> So, at best, each LED is on 1/28 of the time.  This is neglecting the
> time between turning off one segment and turning on the next.  If you
> have an LED rated at 10mA displayed 1/28 of the time, do you need 28
> times the power?  Surely not.  The LED couldn't handle it and we can
> rely on persistence of vision to some degree.

Correct. LED datasheets usually have a duty cycle to amp rating chart.
1/28 is about 3.5 percent duty cycle.

>
> As far as looping through the segments, I would prefer to use a variable
> with one bit set low and then rotate the byte once per segment instead
> of using a jump table.  Either way would work, but I prefer seeing the
> logic in the code.

As you wish! ;-)

>
> If and when I get my code written for this project I plan to share it.
> So, let's see who multiplexes segments first!  :)

Cool. I look forward to seeing it.

BAJ

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