4 Oct
2006
4 Oct
'06
11:51 a.m.
Jules Richardson wrote:
I got to wondering how to make a large numeric display (a few inches
high) for a potential project. I've only seen 7-segment displays up to
about an inch in height, plus I quite fancy something with more rounded
numerals anyway (all of this came about from thinking about Nixies :)
Building something from individual LEDs looks to be cost-prohibitive,
not to mention power-hungry; I think I figured on over about 125 LEDs
per digit.
I came up with something based on 23 segments which I think will look
nice. Basically a 14-segment grid like the following:
_ _
| |
|_ _|
| |
|_ _|
... then with each square part containing a circle split into four
segments. Finally a central segment runs top to bottom to give a '1'
digit centered horizontally. (I'm not going to try and draw arcs in
ASCII ;)
I need to do some tests to see how well light from an LED will travel
through perspex (plexiglass, or whatever the preferred term is) if I
mount the LED at one end of a strip, box off three sides with metal
foil, and (maybe) polish the exposed side. In theory I can easily shape
that to give the arcs that I need, too.
You haven't said what your viewing conditions are -- darkened room,
direct sunlight, etc. There are different display technologies
that can be exploited in each.
Of course all of this is just a precursor to see if
anyone else has
built big displays like this as part of a project, and what they found
worked well (or otherwise)
I built a "display" with 4 ft digits. Very hard to read "up close"
:>
It may be that I can get away with having the curved
sections live
'inside' the boxes (i.e. it won't be noticeable from a distance anyway),
so that there are no points of overlap; time will tell there.
Is there a reason for the aesthetics? Or, "just because"?
Heck of a lot easier driving 23 LEDs per display
rather than five times
that amount, anyway! If it's technically possible, the issue will be how
long it actually takes to make each digit and get it right, though.
Ideas are welcome...
You can buy 14 segment displays (look like British flag).
Your "segments" may well end up being LED "bars" -- which
usually have 3 or 4 discrete lamps in them for more uniform
intensity.
There are displays that use no "static" power (i.e. only
to change state).
You can buy 5x7 LED arrays that are end stackable - though
this is overkill as it allows for the creation of full graphics.
Some vacuum flourescents come with "curved" corners and larger
sizes (look at some of the early pinball machines).
You also need to consider (in your power/intensity budget)
how you drive the displays. I.e. if you multiplex them,
intensity goes down (as does power -- though not proportionately).
I assume you want to do this on a shoestring budget?