1938 Radio Has Awesome Dial

[Mr. Carlson] is truly an old radio surgeon. The evidence? He recently restored an 83-year-old DeForest radio by transplanting an identical chassis from another similar radio. The restoration is fun to watch, but the 7D832 radio dial looks amazing. The dial is very colorful and the wooden knobs and preset selector are beautiful. To seal the deal, the center of the dial has a magic eye tube, giving the radio a retro high tech look.

The donor chassis needed some work before the surgery. In addition, [Carlson] makes some improvements along the way. The radio showed signs of previous service work, which is not surprising after 83 years.

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Meet The Magic Eye Vacuum Tube

Vacuum tubes ruled electronics for several decades and while you might think of them as simple devices analogous to a transistor or FET, there were many special types. We’re all familiar with nixie tubes that act as numeric displays, and there are other specialty tubes that work as a photomultiplier, to detect radiation, or even generate microwaves. But one of the most peculiar and distinctive specialty tubes has an intriguing name: a magic eye tube. When viewed from the top, you see a visual indication that rotates around a central point, the out ring glowing while the inner is dark, like an iris and pupil.

By [Quark48] – CC BY-SA 2.0

These tubes date back to the RCA 6E5 in 1935. At the time, test equipment that used needles was expensive to make, so there was always a push to replace them with something cheaper.  They were something like a stunted cathode ray tube. In fact, the inventor, Allen DuMont, was well known for innovations in television. An anode held a coating that would glow when hit with electrons — usually green, but sometimes other colors. Later tubes would show a stripe going up and down the tube instead of a circle, but you still call them magic eyes.

The indicator part of this virtual meter took the form of a shadow. Based on the applied signal, the shadow would be larger or smaller. Many tubes also contained a triode which would drive the tube from a signal.

There’s a great web site full of information on these venerable tubes and it has examples of these tubes appearing in plenty of things. They frequently appeared in service equipment, radios, and tape recorders. They even appeared in pro audio equipment like the Binson Echorec echo-delay unit.

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Hackaday Links: September 7, 2014

Like Adventure Time? Make your own BMO! It’s a little more expressive than the Adafruit version we saw earlier due to the Nokia LCD. It’s got audio playback too so it can talk to football.

A few years ago, [Matt] made a meat smoker with a PID controller and an SSR. Now the same controller is being used as a sous vide. PID controllers: the most useful kitchen gadget ever.

[Josh] keeps his server in a rack, and lacking a proper cable management solution, this means his rack is a mess. He adapted some Dell wire management arms to his system, using a PCI card bracket to attach the arm to the computer.

[Dr. Dampfpunk] has a lot of glowey things on his Youtube channel

Another [Josh] built a 3D tracking display for an IMU. It takes data off an IMU, sends it over Bluetooth, and displays the orientation of the device on a computer screen. This device also has a microphone and changes the visualization in response to noises.

Remember the pile of failure in a bowl of fraud that is the Scribble pen? Their second crowdfunding campaign was shut down. Don’t worry; they’re still seeking private investment, so there’s still a chance of thousands of people getting swindled. We have to give a shout-out to Tilt, Scribble’s second crowdfunding platform. Tilt has been far more forthcoming with information than Kickstarter ever has with any crowdfunding campaign.

Magic Eye Spectrum Analyzer

its goddamned magic


If Nixies aren’t cool enough, maybe it’s time to step it up to magic eye tubes.

Magic eye tubes are, like Nixies and Dekatrons, display tubes. Unlike the alphanumeric characters of Nixies or rotating points of light in a Dekatron, Magic eye tubes are either bar graph or ‘Pac-Man’ displays that were used to show the signal strength of a radio station on very expensive radio sets.

After doing a few experiments with tubes, [sylvain] thought it would be cool to do something with magic eye tubes. He sourced eight vertical ‘bar graph’ magic eye tubes and built an audio spectrum analyzer.

One of the more difficult things to do was to compute the power levels for each frequency band. There are a few graphic equalizer ICs available, but [sylvian] decided to go the old-school, harder way by putting an FFT algorithm on an ATMega624.

An impressive piece of work that would look amazing next to a nice tube stereo system.

ATtiny Controlled Magic Eye Tube

In the early days of broadcast radio, the most expensive radio sets were extremely impressive pieces of furniture. With beautifully crafted wooden cases polished to a high shine, these wireless receivers were the focal point of any family room. Some of the most expensive radio sets even included a visual indicator signaling the strength of the reception, something [Marcus] decided to re-engineer using an ATtiny85.

The display tube in question is an EM800 magic eye tube, used in radio sets, stereos, and electronic test equipment as a rudimentary display indicator. By applying a control voltage (from 0 to -10V), the illuminated display can be controlled like a bar graph display.

[Marcus]’ tube display is built around an ATtiny85 microcontroller, using a homemade PCB. It’s a fairly simple build, once the issue of supplying 250 Volts to the EM800’s anode is taken care of.

In the video after the break, you can see the bar display of [Marcus]’s magic eye tube slowly growing and receding, perfect for either displaying the current CPU load on your computer or anything else a dynamic bar graph display would be used.

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Kinect Produced Autostereograms (Magic Eye Pictures)

[Kyle McDonald], working collaboratively with [Golan Levin] at the Studio for Creative Inquiry, has come up with an application that can produce autostereograms. These are pictures that appear to be three-dimensional thanks to a visual illusion created by forcing your eyes to adjust focus and vergence differently than they normally would. The program is called ofxAutostereogram and it comes with a couple of examples. Both are show in [Kyle’s] video (embedded after the break), starting with a depth image of a shark. This combines with a texture tile, then is processed through the openFrameworks software in the package to produce the final image.

If that’s all it did you might find it rather unimpressive… these images have been around for some time although they were never so easy to produce on your home computer. But the second example is a pretty fantastic one. You can use a depth image from a Kinect as the starting point. As seen above, there is a preview window where you can adjust the clipping planes in order to include the correct depth. This also allows you a preview of your pose. Once it’s just right, snap a pick and process it through the software.

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