Not Your Typical POV Clock

Persistence of vision displays are fun, and a natural for clocks, but they’re getting a little Nixie-ish, aren’t they? There are only so many ways to rotate LEDs and light them up, after all. But here’s something a little different: a POP, or “persistence of phosphorescence” clock.

[Chris Mitchell] turned the POV model around for this clock and made the LEDs stationary, built into the tower that holds the slowly rotated display disk. Printed from glow-in-the-dark PLA, the disk gets charged by the strip of UV LEDs as it spins, leaving behind a ghostly dot matrix impression of the time. The disk rotates on a stepper, and the clock runs on a Nano with an RTC. The characters almost completely fade out by the time they get back to the “write head” again, making an interesting visual effect. Check it out in the video after the break.

Our only quibble is the choice to print the disk rather than cut it from sheet stock. Seems like there has to be commercially available phosphorescent plastic, or even the glow-in-the-dark paper used for this faux LED scrolling sign. But if you’ve got glowy PLA, why not use it?

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Fail of the Week: [Caleb’s] Phosphorescent CD Player


When [Caleb Kraft] was in full production for Hackaday he pumped a pile of awesome videos. But not every project worked out. He’s been a fan of the Fail of the Week posts, and sent in his own recollection of a project gone wrong. Above you can see his phosphorescent CD player. He prototyped the project in May of last year but technical issues and looming deadlines meant it never saw the light of day. We’ll fill you in on his fail after the jump.

Editor’s note: We need more tips about your own failure! There are a handful of submissions left in our reserves, but to keep this topic as a weekly column we need help tracking down more failed projects. Please document your past failures and send us a link to the write-up. If you don’t have a blog to post it on you may do what [Caleb] has done and email us directly. Remember to include any images and links to video which you may have.

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Laser charged glowing display

Here’s one of the best takes on a glowing display that we’ve ever seen. Currently [H] is using his creation as a fuzzy clock, but it is certainly capable of displaying just about any messages.

The project uses a wheel of luminous paper as the display surface. This has a glow-in-the-dark quality to it which can be charged up using a bright light source. In this case a UV laser diode was used. This is perhaps the best possible source as its intensity will allow for very quick charging. The innovation here is the use of a second disk as a stencil. Look closely in the image above and you will see that the laser diode is mounted perpendicular to the display surface itself. A mirror reflects — and we believe slightly spreads — the laser dot. It then passes through a cut-out on the black wheel which is shaped as the desired character. As you can see in the video after the break, this results in a crisp and clear glowing letter.

Compare this project to the one that moves the diode itself like a plotter and we think you’ll agree this is a simpler implementation which still looks great!

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Laser-charged glow in the dark message board

This entry in the Red Bull Creation contest uses a laser to charge up a glow-in-the-dark message board. The concept is something we’ve seen several times before. Since light can excite a phosphorescent surface, moving pixels of light over that surface leaves a fading trail. Most recently we saw a spinning ring message board. This contest entry is different in that the board is stationary and the print head moves.

It’s basically a two-wheeled robot with a laser diode which can swivel perpendicular to the direction of travel. In this way, the laser prints the rows, and the motion of the robot takes care of advancing the columns. Since laser light has incredible intensity it is able to excite the phosphors much more thoroughly than LEDs. So the message will last longer than that spinning ring project or this awesome turntable hack. Don’t miss the video after the break that shows off the hack along with a bag full of theatrics.

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[Bill Porter] repairs a science museum exhibit

For those who are unfamiliar, “Freeze Frame” is the name of a common display in science museums. It is a small dark room with a single wall covered in phosphorescent material. Opposite of this wall is a flash on a timer. You enter the room, strike a pose and wait for the flash, then view your shadow preserved on the wall behind you.

[Bill] was saddened to see the display at his local science museum had been decommissioned long ago. All that was left was a dark room with a phosphorescent coated wall. Some industrious employees had rigged up some LED pens for people to “draw with light”, but in [Bill’s] opinion this wasn’t as impressive.  He promptly volunteered to rebuild the display himself and we commend him, both on the fantastic job he did as well as his service to his local community. Great job [Bill], keep up the good work.

Visualizing sound without a computer

[Emre] sent in a cool art piece he’s been working on that visualizes your voice without the use of a microcontroller.

The project is called Visible Voice only consists of a laser, mirror, audio speaker and a phosphorescent disk. The laser shines onto a mirror mounted on the speaker and is reflected onto the disk. When an audio signal is played through the speaker, the light bounces off the mirror and produces a waveform on the disk. Think of it as the lowest tech way of building a model of a CRT; the laser is the electron gun and the speaker is a deflection coil.

Right now, [Emre]’s project displays a waveform along a circular path on the slowly rotating phosphorescent disk. Anyone wanting to copy this project could use a moving belt of the same material giving a much more linear (and straighter) waveform trace.

After the break you can see [Emre]’s friend [Ivan] testing out the glowing laser waveform visualizer.

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Brewing up some quantum dots

We’re taking a field trip from the backyard, garage, and basement hacking in order to look in on what research scientists are up to these days. A group from the Johns Hopkins Institute for NanoBioTechnology has been manufacturing quantum dots for use in the medical field. Made up of Cadmium Selenide, this is a nanomaterial that you can think of as individual crystals of the smallest size possible. Quantum dots have many uses. Here, [Charli Dvoracek] takes the recently manufactured dots and activates them with antibodies capable of targeting cancer cells. Once mixed with a biological sample, the dots embed themselves in the walls of the cancer, allowing the researchers to find those cells thanks to the phosphorescent properties of the dots.

The video after the breaks walks us through the various steps involved in growing these dots. [Charli] has the benefit of a fully outfitted lab, using tools like an argon-filled glove box to protect her from harmful off-gases. You’re not likely have this sort of thing in your home laboratory, but as we’ve seen before, you can make some of your own equipment, and produce interesting chemicals with simple processes. If you’re someone who already tinkers with chemistry experiments we want to hear about your exploits so please drop us a tip about what you’re up to.

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