Re: [avr-chat] ATmega88 + triple 7 Segment Display (CC)

[Daniel O'Connor]

On Wed, 12 Mar 2008, David Kelly wrote:
> On Tue, Mar 11, 2008 at 08:53:38PM +1030, Daniel O'Connor wrote:
> > > - Wire each 7 segment display to a digital 8 bit latch.
> > > - Use one data port to send your seven bits of segment data to
> > > all three seven segments via a bus
>
> [...]
>
> > I don't think that will work with this because it's 3 7 segment
> > displays ganged in parallel.
> >
> > The latch idea would work for 3 separate 7 seg displays, however
> > it's probably more sensible to refresh each one frequently (fewer
> > parts needed).
> >
> > If the OP has something like this..
> > http://pdf1.alldatasheet.com/datasheet-pdf/view/168057/ETC/LDT-M514
> >RI.html (although common cathode instead)
> >
> > Then they will need to update each separate display often enough so
> > the user doesn't see any flicker (50Hz+).
>
> Driving the LED with a latch doesn't flicker, even if its updated
> once every 5 minutes. All segments which are illuminated are driven
> by an output bit on the latch.

Yes I know, but it won't work with what the OP has because you can't 
access all of the LEDs individually. It would work if you had 3 7seg 
displays of course.

> When one is operating with a limited power budget and for some reason
> must drive LED display not LCD then one can save power by
> multiplexing where only one segment of the display array is driven at
> a time, driven hard and fast moving on to the next before the eye
> notices. This is common with LED calculators and watches.

It's not a power thing - it's the only way you can drive a triple-7 
display..

-- 
Daniel O'Connor software and network engineer
for Genesis Software - http://www.gsoft.com.au
"The nice thing about standards is that there
are so many of them to choose from."
  -- Andrew Tanenbaum
GPG Fingerprint - 5596 B766 97C0 0E94 4347 295E E593 DC20 7B3F CE8C

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