Custom circuit drives a small round CRT display

[Svofski's] latest hack seeks to do no more than look cool on his desk. We’d say mission accomplished. He doesn’t even need anyone around to be proud of the small round CRT display unit he put together. Just having it hum away next to him will be more than enough to keep him going when regular work gets a bit tedious.

One of the biggest challenges when working with a cathode ray tube is the supply. He compares the requirements with that of Nixie tubes, and this is quite a bit more challenging since he wants to generate the 750V from a 12V DC source. To pull it off he hand wound his own transformer. There are two secondary coils, one for the cathode heater and the other as the supply. You can see a brief clip of the unit in action after the break.

Take note of the PCB section of his writeup. He took a meandering route through several different software packages before printing the board. It started with Eagle, moved to, which produced a Specctra file that he converted to gEDA using a Python script.

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Two-player Tic-Tac-Toe from logic chips

Here’s another entry in the 7400 Logic contest. [Circuitchef] used gates and a few flip-flops to build a two-player electronic Tic-Tac-Toe game. The full details or shared in the PDF file he links to in his post. We’ve also linked to it after the break in case the Dropbox he is using becomes unavailable.

He provides a nice block diagram which helps to understand the game’s design. The board is arranged in a 3×3 matrix of momentary push buttons and bi-color LEDs. Each player takes turns pushing the button in the square they’d like to claim. The input circuitry uses flip-flops to establish which player’s turn it is, illuminating the appropriate color for that square. A set of 3-input AND gates monitor all possible combinations of winning patterns. The outputs of those gates are OR’d down to just one output which is used to light up the ‘Winner’ LED with the right color. If all boxes are lit up and none of those combinations is satisfied the game is declared a draw. This can all be seen in the demo embedded below the fold.

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Building your own Fusion Drive

We missed the original announcement, but Apple unveiled more than just the iPad Mini at their last event. They’ve got a new storage system called Fusion Drive which is supposed to combine the access speeds of solid state with the storage density of platter drives. When you look just under the surface what you’re really seeing is a disc drive with grossly enlarged cache in the form of an SSD drive. How about moving from the 64 MB or so of cache seen on many large hard drives today to something like 64GB?

Well you don’t have to wait for Apple to do it. [Patrick Stein] gave it a shot using command line tools to combine an SSD with a physical drive. Sure, it’s not an all-in-one solution, but it is a pretty good proof. The linchpin that will really make it possible is a low-level driver that can handle the caching on the SDD, while ensuring that the data eventually makes it to the platter for long-term storage.

[via Engadget]

Collection of Nixie bar graphs bump to the beat

This VU meter uses Nixie tubes as the display. There are a total of fourteen IN-13 bar graph tubes that map out the audio spectrum. The build uses purely hardware for the display; no microcontroller processing, or dedicated VU-meter chips were used.

Input begins with a dual Op-Amp along with a pair of potentiometers which allow the left and right channels to be balanced. Both channels are then each split into seven signals, which explains the layout of tubes seen above. Each signal is then fed through a voltage divider to envelope the output between 0V and 6V. There is also a low-pass filter to handle sudden volume spikes which don’t work well with the nixies. But as shown in the video after the break, all that work has paid off. Thr clip gives us a look at the green protoboards which host all of this filtering hardware. You’ll want to turn the volume down for the first couple of demonstrations which use a sweep to test the system.

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[Lou's] haircut really sucks

Ah yes, at some point a brilliant inventor combined the electric trimmer with a vacuum cleaner and the art of cutting hair was never the same again. [Lou] is showing us how to give a haircut that really sucks up the waste. And he did it using rubbish he had lying around.

Most people will recognize this as a DIY version of the Flowbee. Not surprisingly, you can still buy one of those if you want, but [Lou] is looking for a vacuum cutter for trimming his dog’s hair so he’s not about to shell out cash for it. He already has the trimmer, and just needed a way to attach the vacuum hose to it. In the image above you can see the grey crevice attachment for his vacuum. He taped it onto the trimmers, then cut a plastic soda bottle to use as a hood near the business end of the trimmer. It’s all wrapped in packing tape to hold everything in place and seal around the joints. You can see it in action in the clip after the break.

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Beginner project: Color Sensing with RGB LEDs and a photocell

I’ve seen the concept art for “real world eyedroppers” several times. I haven’t noticed any of the products come to market though. It isn’t the technology stoping them, color sampling can be done a million ways. I picked one of the easiest ways and tossed something together pretty quickly.

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LED fun and Light Painting with the pyMCU


Recently [Richard] at [pyMCU] was nice enough to send me one of their units to try out. As featured here before, this little board allows you to control physical things using your computer and the Python programming language. After evaluating it and making a LED blink, there were a couple other LED projects I wanted to try.

The first idea was to make a LED chaser. This was quite simple, using a little code and plugging in a few LEDs. From this, since you can make the LEDs chase each other, then in the right sequence it should be able to be used to display images using long-exposure photography. Be sure to check out the video after the break of this 10 LED chaser/light bar being assembled.

The results of this LED light bar experiment were really cool, writing some simple text and image with 10 LEDs. Considering the low component count, this is one of the simplest light bar builds that we’ve seen. Programming was simple as well, since the computer using Python does all the processing of the drawing as well as physically turning the LEDs on and off. Of course this setup isn’t without its limitations, having to be connected to a computer being the most obvious. [Read more...]