[Tim] recently found himself tinkering with a cheap string of LEDs. Far from an advanced, IC-controlled addressable set, these were merely a string with LEDs of four colors that could be switched on and off. However, digging in to the LEDs themselves turned up a curious find.
The LEDs were set up in a parallel/anti-parallel fashion. The two power lines ran the length of the string, with all the LEDs installed across them. If polarity was applied in one direction, the red and yellow LEDs would light up, in the other, the blue and green LEDs would light together.
This raised a question for [Tim], as typically, different LEDs light up at different forward voltages and this can cause issues when running different color LEDs in parallel together. What he instead found was that all the LEDs were actually blue LEDs in their fundamental construction. However, the red, yellow, and green LEDs had all been given a phosphor coating. In these devices, when the blue LED underneath lit up, the phosphor converted the light into the desired color. [Tim] was able to confirm this behaviour by illuminating the phosphor manually using an external UV-A LED.
It’s an interesting choice, but it’s certainly one way of making a multicolored string of LEDs. If you wanna get fancier though, consider studying this tutorial on working with addressable LED strings!
[Thanks to J Peterson for the tip!]
We love seeing old technology brought back to life, especially when it’s done in the context of how the device was originally intended to be used. And double points when it’s space gear, like what [Curious Marc] and his usual merry band of cohorts did when they managed to light up a couple of real Apollo DSKY displays.
The “Display and Keyboard” formed the human interface to the Apollo Guidance Computer, the purpose-built machine that allowed Apollo missions to fly to the Moon, land safely, and return to Earth. Complete DSKYs are hard to come by, but a lucky collector named [Marcel] was able to score a pair of the electroluminescent panels, one a prototype and one a flight-qualified spare. He turned them over to AGC guru [Carl Claunch], who worked out all the details of getting the display working again — a non-trivial task with a device that needs 250 volts at 800 Hertz.
The first third of the video below mostly concerns the backstory of the DSKY displays and the historical aspects of the artifacts; skip to around the 12:30 mark to get into the technical details, including the surprising use of relays to drive the segments of the display. It makes sense once you realize that mid-60s transistors weren’t up to the task, and it must have made the Apollo spacecraft a wonderfully clicky place. We were also intrigued by the clever way the total relay count was kept to a minimum, by realizing that not every combination of segments was valid for each seven-segment display.
The video has a couple of cameos, like [Ben Krasnow], no slouch himself when it comes to electroluminescent displays and DSKY replicas. We also get a glimpse of well-known component slicer and MOnSter 6502-tamer [TubeTime] too. Continue reading “Apollo DSKY Display Glows Again”
There are hundreds if not thousands of artifacts from the Apollo program scattered around the globe, some twisted wrecks at the bottom of the ocean, others lovingly preserved and sitting in museums or in the hands of private collectors. All of what’s left is pretty much pure unobtainium, so if you want something Apollo-like, you’re probably going to have to make it yourself.
[Ben Krasnow] took up the challenge to make an electroluminescent Apollo-era DSKY display from scratch, with outstanding results. The DSKY, or “display and keyboard”, was the user interface for the Apollo Guidance Computer, the purpose-built digital navigation system that got a total of 24 men there and back again. [Ben] says it took a long time to recreate the display, and we can see why. He needed to master quite a few skills, including screen printing to get the glass-panel display working. The panel is a sandwich of phosphorescent paint, a dielectric, and conductive ink. The ink is silkscreened on the back to form the characters, all applied to indium tin oxide (ITO) conductive glass. A PCB with the same pattern of character segments lays behind that, driving each segment with 300 volts or so through a trio of HV507 high-voltage shift registers. It’s an impressive bit of engineering and gives off a decidedly not-homebrew vibe.
In the video below, [Ben] goes into detail about the trials he experienced on the way to this amazing endpoint, not least of which was frying chip after chip due to ineffective protection diodes in the shift registers. That’s an epic debugging story that’s worth the price of admission all by itself. It’s not the only DSKY in town, of course – [Fran Blanche] has been working on one for a while too – but there’s just something about that blue glow that we really like.
Continue reading “[Ben Krasnow] Makes A DSKY”
Phosphors are key to a whole swathe of display and lighting technologies. Cathode ray tubes, vacuum fluorsecent displays, and even some white LEDs all use phosphors to produce light. [Hydrogen Time] decided to make a green phosphorescent material, and has shared the process on Youtube, embedded below.
The aim is to produce zinc sulfide crystals doped with copper impurities. This creates a phosphor with a familiar green glow. [Hydrogen Time] starts by noting that it’s important to make sure all chemicals used are of good quality, as even slight impurities can spoil the final product.
Zinc sulfide is made into an aqueous solution, before a highly diluted copper sulfate solution is added, along with ammonium chloride to act as a flux. The mixture is stirred, before being heated in a tube flushed with argon. After firing, the phosphor is washed with water and allowed to cool.
The final product is demonstrated to glow a vibrant green under UV light, showing the process to be successful. [Hydrogen Time] intends to use the homebrew phosphor in future work to produce a display. It recalls us of [Jeri Ellsworth], producing her own EL wire at home. Video after the break.
Continue reading “Make Your Own Phosphorescent Material”
If you’ve ever wanted to sit at the console of the machine that started the revolution in interactive computing, your options are extremely limited. Of the 53 PDP-1 machines that Digital Equipment Corporation made, only three are known to still exist, and just one machine is still in working order at the Computer History Museum. So a rousing game of Spacewar! on the original hardware is probably not something to put on your bucket list.
But thanks to [Hrvoje], there’s now an FPGA emulation of the PDP-1 that lets you play the granddaddy of all video games without breaking into the CHM. The project was started simply to give [Hrvoje] a sandbox for learning FPGAs and Verilog, but apparently went much further than that. The emulation features the complete PDP-1 instruction set, 4kB of core memory, and representations of the original paper tape reader, teletype, operator’s console, and the classic Type 30 CRT. All the hardware is displayed on a standard HDMI monitor, but it’s the CRT implementation that really sells this. The original Type 30 monitor used a CRT from a radar set, and had long-persistence phosphors that gave the display a very distinctive look. [Hrvoje] replicated that by storing each pixel as three values (X, Y, and brightness) in a circle of four chained shift registers. As the pixels move through the shift registers, the brightness value is decreased so it slowly fades. [Hrvoje] thinks it doesn’t look quite right, but we’ll respectfully disagree on that point.
We’ve argued before that the PDP-1 is the machine that started hacker culture, and we think this project is a fitting tribute to the machine as we enter the year in which it will turn sixty. Having the chance to play with it through this emulation is just icing on its birthday cake.
Continue reading “FPGA Emulates A PDP-1, Breathes New Life Into Classic Video Game”
Pity the aficionado of rare vintage displays. While Nixies and VFD tubes get all the attention and benefit from a thriving market to satisfy demand, the rarer displays from the mid-20th century period are getting harder and harder to find. One copy of an especially rare display is hard enough to find. Six copies for a clock? That’s a tall order.
That doesn’t mean you can’t fudge it, though, which is how this faux-NIMO clock came to be. [Paul Bricmont] was inspired by [Fran Blanche]’s NIMO tube primer, wherein the rare, single-digit CRT display was put through its paces. We’ve got to admit, it’s an easy display to fall in love with, thanks to its eerie blue phosphor glow, high voltage supply, and general quirkiness. [Paul] was unable to lay hands on a single tube, though, so he faked it with six tiny TFT displays and some plastic lenses. The lenses mimic the curved front glass of the original NIMO, while the TFT displays provide the stencil-style images of each numeral. The phosphor glow comes from replacing the stock white TFT backlight with a Neopixel array that can produce just the right shade of blue-green. 3D-printed modules hold two digits each, and the usual Arduino components run the show. The effect is quite convincing, although we bet some software tweaks could add things like faux burn-in and perhaps soften the edges of the digits to really sell it.
What other rare displays could be replicated this way? Given the variety of displays that were tried in the pre-LED era, it may be a rich vein to mine.
We’ve all had the heartbreak of ordering something online, only to have it arrive in less than mint condition. Such are the risks of plying the global marketplace, only more so for used gear, which seems to be a special target for the wrath of sadistic custom agents and package handlers all along the supply chain.
This cruel fate befell a vintage Vectrex game console ordered by [Senile Data Systems]; the case was cracked and the CRT was an imploded mass of shards. Disappointing, to say the least, but not fatal, as he was able to make a working console from the remains of the Vectrex and an old IBM monitor. The Google translation is a little rough, but from what we can gather, the Vectrex, a vector-graphics console from the early 80s with such hits as MineStorm, Star Castle, and Clean Sweep, was in decent shape apart from the CRT. So with an old IBM 5151 green phosphor monitor, complete with a burned-in menu bar, was recruited to stand in for the damaged components. The Vectrex guts, including the long-gone CRT’s deflection yoke assembly, were transplanted to the new case. A little room was made for the original game cartridges, a new controller was fashioned from a Nintendo candy tin, and pretty soon those classic games were streaking and smearing across the long-persistence phosphors. We have to admit the video below looks pretty trippy.
If arcade restorations are your thing, display replacements like this are probably part of the fun. Here’s a post about replacing an arcade display with a trash bin CRT TV, an important skill to have is this business.
Continue reading “Trashed Vector Game Console Revived With Vintage IBM Monitor”