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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Generating random numbers from white noise

Even though rand() may be a good enough random number generator for making a video game, the patterns of random bits it spits out may not be sufficient for applications requiring truly random data. [Giorgio] built his own random number generator, and after many statistical tests it ended up being random enough for a few very complex calculations.

Previously, we saw [Giorgio] generate random numbers with a Chua circuit, but for all the complexity of building an electronic strange attractor there’s actually a much simpler source of random data: a white noise generator.

[Giorgio]‘s random number generator for this project is just a pair of resistors, with an op-amp buffer, amplifier, and current switch to turn analog data into a digital output of random 1s and 0s. [Giorgio] sampled this data by plugging the digital out into one of the GPIO pins of a Raspberry Pi and recording the data with s small script.

To verify his sequence of bits was actually random, [Giorgio] performed a few tests on the data, some more reliable in determining randomness than others.

Because every project needs a few awesome visualizations, [Giorgio] plotted each sequence of bits as either a black or white pixel in a bitmap. The resulting image certainly looks like television static, so there are no obvious problems with the data.

[Giorgio] also performed an interesting Monte Carlo simulation with his megabytes of random data: By plotting points on a plane (with a range from 0,0 to 1,1), [Giorgio] can approximate the value of π by testing if a point is inside a circle with a radius of 1. The best approximation of pi using 10,000 points of random data came out to be 3.1436

Of course [Giorgio] put his random data through a few proper statistical tests such as rngtest and dieharder, passing all the tests of randomness with flying colors. An interesting build that shows a small glimpse of how hard generating really random numbers actually is.

Drag and drop code onto this ARM dev board

On the continuing list of homebrew ARM dev boards we’ve seen over the past few months, [Squonk42]‘s USBug is one of the best we’ve seen. Like many other ARM boards, it breaks out a member of the Cortex M0/M3 family into a 40-pin DIP, but unlike all the others, [Squonk] designed it so you can drag and drop code onto the microcontroller just like a USB thumb drive.

[Squonk]‘s trick relies on a certain breed of NXP LPC11xx/LPC13xx microcontrollers. These chips feature a ROM-based mass storage, meaning you can compile code on your desktop and simply shuffle it over to the USBug, no external programmer required. Here’s the relevant app note (PDF in a zip file. Double whammy).

Of course, the USBug features the I/O you’d generally expect from the current crop of Cortex-M3 devices, all while serving up 64 kB of Flash and 12 kB of RAM.

[Squonk] says he’d like to put the USBug on Kickstarter, but unfortunately he’s not a US citizen. In the spirit of Open Hardware, perhaps some maker-based electronics manufacturer will pick up where [Squonk] is forced to leave off.

Log guitar uses tube as a bridge, actually is the blues

In the never ending quest to replicate the tone of depression-era blues records, [Valve Child] managed to build the most backwoods guitar ever seen.

The body of [Valve Child]‘s slide guitar was taken from the limb of a red gum tree felled during a wind storm. After taking a chainsaw, router, and sander to the guitar, [Valve] sealed it with linseed oil.

The real beauty of this build comes from the bridge and electronics: the pickup is made from six stacks of magnets encased in hot glue and wound with enamel wire. The bridge of the guitar is actually made from a 6GM8 dual triode. Not only does this provide the guitar with a wonderful brassy sound, the tube serves as a wonderful low-tech preamp when powered by a 6 volt battery.

The three strings on the guitar are tuned DAD, perfect for the likes of [Robert Johnson], or, for the younger kids, [Jack White]. Surprisingly, [Valve Child]‘s guitar actually sounds really good. as heard in the video demo after the break.

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More LED Madness!

So last week [Caleb] posted an article about hacking a floating LED ball.  In response, here’s a couple simple LED hacks or repurposings that I’ve come up with recently.


LED Solar Glow Cube: If you’ve ever seen path lights lighting up people’s gardens or walkways you may have wondered what components they had in them and how they could be repurposed.  As shown in this article, there’s not much too them other than a circuit board, rechargeable battery, and, of course, a solar panel. Combine this with some leftover foam with a hole in it, and you have the device pictured above.  Really simple, but the results are pretty cool as seen in the video after the break.

LED light-nunchucks

LED Nunchucks: If you thought that wheel lights were only for actual wheels, than you haven’t seen these nunchucks built with some PVC pipe and acceleration-sensitive wheel lights. This may not be much of a “hack” in that they are quite easy to build, but the results are pretty neat, being fun to sling around or even for use in long-exposure photography.  Check out the videos after the break of these nunchucks in action and of some LED light paintings that can be made with them. [Read more...]