Turning A Tiny CRT Into A Monitor


[GK] picked up a few tiny 2″ CRTs a while back and for the longest time they’ve been sitting in a box somewhere in the lab. The itch to build something with these old tubes has finally been scratched, with a beautiful circuit with Manhattan style construction.

[GK] has a bit of a fetish for old oscilloscopes, and since he’s using an old ‘scope tube, the design was rather simple for him; there aren’t any schematics here, just what he could put together off the top of his head.

Still, some of [GK]‘s earlier projects helped him along the way in turning this CRT into a monitor. The high voltage came from a variable output PSU he had originally designed for photomultiplier tubes. Since this is a monochrome display, the chrominance was discarded with an old Sony Y/C module found in a part drawer.

It’s a great piece of work that, in the words of someone we highly respect is, “worth more than a gazillion lame Hackaday posts where someone connected an Arduino to something, or left a breadboard in a supposedly “finished” project.” Love ya, [Mike].


Watch a shop tour through the screen of an oscilloscope

[Alan] posted a video tour of his electronics shop, but you’ll be viewing it through the green screen of an oscilloscope. The image above is a video camera filming a scope screen which displays the image of…. an oscilloscope (insert your own Yo Dawg meme here). But first he shares the technique he uses to display composite video on an oscilloscope screen.

The first three minutes of the video after the break are devoted to the video display hack. He starts with a glimpse of the breadboard circuit which takes the composite video signal and provides the necessary X, Y, and Z input signals to the scope to perform like this. He then walks through each portion of the schematic, which is based on an LM1881 video sync separator chip. The horizontal and vertical sync signals are separated by this chip, then filtered to produce ramp voltages for each to drive X and Y. The Z-axis is fed through a simple inverter circuit; Bob’s your uncle and your oscilloscope is now a TV monitor.

Of course this is not the first time this has been done. But we loved [Alan's] presentation, and thought the shop tour was a fun way to finish off the video.

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Composite video with MSP430 chip

[NatureTM] used part of the Thanksgiving holiday to get composite video output working with an MSP430 microcontroller. He’s using one of the chips that came with the TI Launchpad, which is a big hardware limitation because of the relatively small code memory and RAM. The chip displays one still image at a resolution of 192×40 pixels. Still, this is a great way to learn about composite video signals, as a lot of other projects use a TVout library to save you the headaches. All you’ll need is a TI Launchpad, a 16 MHz crystal oscillator, two resistors, and an RCA jack. Dig through the code and see what a great job [NatureTM] did of offloading as much work onto the chip’s peripherals as possible.

Microscope camera adapter

[Ben Krasnow] is capturing some great snapshots using a microscope adapter and some tricks. The camera attachment is just a lens adapter ring with a tube added. Unlike other microscope imaging hacks we’ve seen he used a real microscope but found that the pictures had a bit of light distortion to them. The camera sensor was picking up a glare reflected on the inside of the black tube. By adding a washer and repositioning the apparatus he got over that hurdle. The final part of the puzzle is image processing. By taking several pictures at different focal lengths and compositing them he gets killer photos like the compound eyes of that house fly seen above.

DIDJ composite video out

[Nirvous] managed to get composite video out working on the DIDJ. He knew that the CPU had the ability to generate the signal, and that similar devices already had this capability. After studying some DIDJ teardowns he figured out which connection on the processor should provide the appropriate signal. Next was the firmware side of things and after sifting through a lot of code he was pleased to find a flag that looked like it would enable video out. Some cross-compiling, soldering, and a low-pass filter got it to work.

If you’ve been hacking around on the device you might try this. The CPU uses a ball grid array so soldering is a bit difficult. We covered a BGA soldering trick that might be just the thing so check it out before you retreat into your soldering-fortress of solitude.

Phasor A/V PAL demo uses ATmega88

Above is a new demo video called Phasor developed by [Lft]. It is run from an AVR ATmega88 and a few passive components, and the result is pretty amazing. [Lft] goes into detail about the tricks he used to get this up and running. The chip is clocked at 17.73447 MHz which is exactly four times the frequency of the PAL color carrier wave which allows him to fake a smooth signal. He also uses a timer trick to get the voltages that he needs. The work done here is beyond hardcore and quite frankly we can’t believe he managed to fit all of this into 8.5 KB of program space with just 1 KB or RAM. We wonder if there’s enough room there to add sound and color to the AVR Tetris project.

[Thanks Sprite_tm]

More AVR Tetris

[Ben] built an AVR based Tetris game that uses a TV as the display. He linked his project in a comment from the AVR Tetris project featured last week. His work taps the power of his own tvText library to handle the composite video out. Using a TV takes all of the hardware work out of the equation, leaving just the composite jack and a few buttons to connect to the ATmega168 and its 20MHz clock. We’ve embedded the game play video after the break. It’s black and white but also clean and crisp.

[Ben] didn’t include music with his build but another commenter, [Eric], has started to work on that. We can’t help but think that they both should have tipped us off sooner about their projects.

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