Making large numeric displays

Brent Hilpert hilpert at cs.ubc.ca
Wed Oct 4 16:33:47 CDT 2006


The following may-or-may-not suit the esthetics you want to achieve, but it
certainly would have a retro/low-tech aspect to it:

Revert to the 10-layer technique used in the early-mid-sixties.
Each digit is made up from 10 layers of clear plastic, where each layer has
dimple/dots/pixels forming 1 of the 10 numerals. Light is injected into a
layer from the side and refracts out when it hits the dimples.

The orginals used incandescent lamps of course, and can be found in early
Canon calculators, General Radio digital test equipment, and occasional other
bits of equipment.
See http://www.vintagecalculators.com/html/canon_canola_130s.html (great pictures)
 or http://www.oldcalculatormuseum.com/canon161.html

(I believe the units from General Radio were actually larger, perhaps 1.5-2 inches
digit height.)

(Trivia: These displays can be seen on the countdown timer on the atomic bomb
in James Bond - Goldfinger.)

It does have the disadvantage (as with Nixies) of interference from all the
layers, but you also get that cool 3-D effect as the numerals change.

Obviously this technique could be updated with LEDs and scaled up in size.
A little experimenting might show whether it would be worthwhile in terms of
LED count vs brightness, etc.

It would probably be even easier to make in larger form as there would be more
space for positioning and isolating LEDs at the edges, and interference
effects might be reduced by being able to make a finer dimple pattern. As well
it might be possible to make each layer just a rectangle and avoid any bending
or tabs.

Make up a drilling template for each numeral and just drill partially into the
layer to form the dimples, the end of a drill bit leaves a surface perfect
for refracting/diffusing the light out.

Or farm it out to a plastic-machining shop with a computer-controlled-machine,
they could zip off multiples in no time.



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