Faux CRT Glow

Do you know any flat-screeners? What’s that? You have never heard of a flat-screener? We better start off with a totally unbiased definition in that case: flat-screener (noun) — a person who mistakenly believes that the best display technologies have flat screens.

Being nearly two decades into the era of the flat-screen TV, there are many poor flat-screeners out there that have never experienced the glory of a CRT display. They have no idea that inside those bulky and heavy cases with an outdated appearance, there is a display mechanism that many retro gamers and graphic artists believe is superior to modern technologies. This unique mechanism gives CRTs superior color accuracy, high contrast ratios, and smoother motion rendering in the eyes of many.

Flat-screeners are winning the battle, however, so you can no longer pick up a CRT display at your local electronics store. If you want one, you have to either purchase it second-hand and risk having a delivery person smash its delicate components to pieces, or do what bitluni did and create your own imitation of one of these classic displays.

To be clear, bitluni’s creation does not actually operate on the same principles as a CRT display, but it does a reasonably good job of mimicking one. The idea for this build came about when bitluni noticed that glowing PLA materials are highly sensitive to UV light, and the glowing persists for some time after the light is removed. This allows patterns to be drawn on the material by tracing a laser over it. The effect is reminiscent of how the phosphors that coat the screen of a CRT display emit visible light when they are excited by an electron gun.

To be of much use for a display, the laser needs to be precisely controllable and capable of very fast movement. Early tests with speakers and servos proved to be unworkable for one reason or another, so bitluni made a custom control system from stepper motors and mirrors. The stepper motors control the x-axis of one mirror, and the y-axis of the other. The laser shines on one mirror, which in turn directs the light to the other mirror before it is reflected onto a sheet of glowing PLA.

This hardware was controlled by an Arduino Nano development board, a CNC shield, and a motor driver. A 405 nanometer laser scavenged from a pointer served to excite the PLA. These components were then fitted into a 3D-printed enclosure that looked just like a miniature CRT TV. A rotary encoder and switch were added in to turn the device on and navigate a menu. BNC connectors were installed to carry the x- and y-axis control signals, and also to turn the laser on and off.

As a first test, bitluni hooked the faux TV up to an oscilloscope’s waveform generator. The patterns were clearly visible, although it could only operate in the single-hertz range, so it was not exactly quick to update the screen. This is, of course, due to the relatively slow movement of the stepper motors, but the persistence of the material’s glowing effect still allowed the display to draw some fairly complex patterns. A screen filled with text was no challenge for the TV, and bitluni even proved that it is a good platform for Rickrolling an unsuspecting victim.

This project may not be all that useful, but it does look like a lot of fun to play with. I can’t be the only one that wants to see this thing play Pong — that glowing amber screen and the tracers would be just about perfect for it.