| IEE 10000-1819-B Projection Display | |
| Written by AnubisTTP on 2007-10-18 |
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Before the arrival of reliable, easy-to-use LED displays like the Monsanto MAN-1, companies came up with a vast array of impractical methods to display numbers and characters. Projection displays, such as the one shown here, are one of these fringe display types, and were designed to compete directly with the neon filled Nixie tubes that were the leading display of the time. Also known as a "One Plane Readout" or "In Line Display", these devices were invented by IEE in 1956 for use in their proprietary industrial control systems; the devices proved so popular with customers that IEE began producing and selling the displays as a stand-alone product.
A projection display functions like a miniature slide projector, only the "slides" are numbers, each with its own separate lamp for electrical control. In this IEE display, light from one of 12 different lamps is projected through one of 12 focusing lenses, which directs the light beam onto the appropriate number mask. Light exiting the digit mask passes through a second set of lenses, which bends the light to project the image of the digit mask onto the center of a fogged plastic screen at the front of the display.
Projection displays are complex devices with numerous parts, and were expensive to manufacture compared to a Nixie tube. For the modern hobbyist though, projection displays have several significant advantages over shaped cathode displays like Nixie tubes. Projection displays have replaceable bulbs, allowing the color of the displayed number to be changed simply by replacing the bulb with an appropriate LED light source. The digit masks in most projection displays are also replaceable, which allows for many custom display types to be quickly and easily produced. During the Cold War projection displays were quite popular for industrial control systems, since custom symbols and warning messages could be easily added to the digit mask.
IEE referred to projection displays as "In-Line" displays because the digits were displayed on a single plane instead of stacked as in a Nixie tube.
IEE projection display, exploded view.
The slides in a projection display are easy to replace; transparency prints and a fistful of RGB LED's allow the home experimenter to coax these devices into displaying nearly any symbol imaginable.
IEE projection display, cutaway diagram.
This module contains seven IEE 10000 projection displays mounted to a shared front screen.
Various different models of IEE projection displays for scale
comparision; from left to right: 340 series, 14928 series, 01100 series, 220H series, 00010 series, 10000 series. Note that IEE projection displays utilize composite part numbers and everything occurring after the first dash is encoded information about lamp voltage and character
sets.
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