> > Re-attached in case anyone saved it
>
> Ahh, that makes more sense now :) thanks.

Sorry about the first one. It was clipped from a larger diagram
that I did recently. Just one of those little proof-reading bugs

You didn't say whether these were common anode or common
cathode. You may find it simpler to use a 7-segment driver like
the 4511 to drive the LEDs directly. It has a 3-18V supply range.
and at 8V you might just get away with a 5V logic "1"

> I'm trying to get some large LED digits going - I put 20 mA thru
> them and measured about 7.5 volts drop across them

You may find conditions change when you go from static drive
to a dynamic strobing drive. Timing to get even brightness is
important. I notice on buses that the destination displays are
quite patchy, and a mix of yellow and amber, doesn't look good.
Readable but ugh

A fail-safe circuit is desirable so you don't burn out the LEDs in
a fault. Although 7-segs seem to be quite hardy. One display I
made accidentally got switched to 12V supply instead of 5V.
After a couple of minutes I got a whiff of "that smell" and turned
the power off (spotting the 12V switch position). All of the displays
and driver chips were stinking hot, but were fine after they cooled
down

> they have stopped selling the green ones.

RadioSpares, Active Components and probably Arrow sell
red, yellow, orange, bicolour and green 7-segment and
starbursts. Or you could make your own using discrete LEDs.
AFAIK 7-seg aren't available in white, blue or RGB. If you
could afford to make your own out of these they would look
quite something

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