POV Display Does it on the Cheap

lowBudgetPOV

[Sholto] hacked together this ultra low-budget spinning display. He calls it a zoetrope, but we think it’s actually an LED based Persistence Of Vision (POV) affair. We’ve seen plenty of POV devices in the past, but this one proves that a hack doesn’t have to be expensive or pretty to work!

The major parts of the POV display were things that [Sholto] had lying around. A couple of candy tins, a simple brushed hobby motor, an Arduino Pro Mini, 7 green LEDs, and an old hall effect sensor were all that were required. Fancy displays might use commercial slip rings to transfer power, but [Sholto] made it work on the cheap!

The two tins provide a base for the display and the negative supply for the Arduino. The tins are soldered together and insulated from the motor, which is hot glued into the lower tin. A paper clip contacts the inside of the lid, making the entire assembly a slip ring for the negative side of the Arduino’s power supply. Some copper braid rubbing on the motor’s metal case forms the positive side.

[Sholto] chose his resistors to slightly overdrive his green LEDs. This makes the display appear brighter in POV use. During normal operation, the LEDs won’t be driven long enough to cause damage. If the software locks up with LEDs on though, all bets are off!

[Sholto] includes software for a pretty darn cool looking “saw wave” demo, and a simple numeric display. With a bit more work this could make a pretty cool POV clock, at least for as long as the motor brushes hold up!

[Read more...]

The Persistence of Jumping Rope

POV Jump Rope

[Antonio Ospite] recently took up jump rope to increase his cardio, and also being a hacker decided to have some extra fun with it. He’s created the JMP-Rope — the Programmable Jump Rope.

He’s using the same principle as a normal POV (Persistence of Vision) display, but with a cool twist. He’s managed to put the microcontroller (a Trinket) and battery into the handle of the jump rope. Using a slip ring system, the RGB signal gets passed to the rope, which contains the LEDs. It’s a pretty slick setup, and he’s written another post all about how he did the hardware.

To create the images for his JMP-Rope, he’s outlined the steps to a successful POV image on his blog. These include re-sizing the image to a circle (duh), reducing the color palette, and then performing pixel mapping using a discrete conversion (from polar to Cartesian coordinates). After that it’s just a matter of representing your new-found pixel map in a 1D animation, played column by column. [Antonio] stores these frames on the micro-controller as an RLE (run length encoded) indexed bitmap.

Stick around to see how he made it, and some other cool examples of what it can do!

[Read more...]

Persistence of Vision would make a Great HUD

povtyp

[Eduardo Zola] has just put the finishing touches on this awesome real-time persistence of vision display which displays text as you type!

It looks like the display is mounted on a small DC fan, which [Eduardo] powers using a bench top power supply. This allows him to fine tune the speed manually, without adjusting the the actual POV controller. The display receives the characters from the keyboard via a small USB RF receiver, and it has got a pretty snappy response time.

There isn’t too much more info on the project, but it certainly gives us an idea — could persistence of vision be used to create a kind of heads up display in a vehicle? What do you think?
[Read more...]

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

fotw-caleb-hackfail

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.

[Read more...]

Ghostly images captured only on camera

is that a logo

A while back our good buddy [Ch00f] built a QR code clock, unreadable to both humans and computers. A human couldn’t read the clock because of the digital nature of a QR code, and because the clock used persistence of vision in driving the LEDs, a digital camera can’t capture all the pixels in the QR code at the same time. It’s a highly useless but impressive art piece. Now, [Ch00f] is turning that build on its head. He created a rudimentary display that is invisible to the human eye, but easily detected with a digital camera.

This build exploits a basic property of CMOS digital cameras – the rolling shutter. Because it takes time to get pixels off a modern digital image sensor, each picture is actual a composite of many different strips, each taken slightly out of sequence. You can see this for yourself by taking a picture of something rotating very fast with your camera phone; a picture of an airplane propeller will make the blades appear curved, or look like [Dr. Seuss] has an aeronautical engineering degree.

To create his display, [Ch00f] found a few inexpensive fiber optic lights. By aligning a few of these into columns and lighting them up in a precise sequence, he can exploit the rolling shutter and make an image appear. To the human eye, it looks like a solid wall of illuminated fiber optics.

As for how practical this build is, [Ch00f] says not much. For cell phone cameras, you’d need to have a very, very short exposure time for this to work. The only way to do that is to make this display unbelievably bright, or just put it out in the sun. We can’t see that being practical for any potential use case, but we’d be more than happy to see a large-scale attempt at displaying images with this technique.

POV Pong game uses all kinds of smart design

pov-pong-game-uses-smart-design

This little device lets you play some head-to-head pong using a spinning LED display. We’re really in love with the design. You get a pretty good idea of the Persistence of Vision aspect of the build by looking at this picture. But hearing [Dennis] explain the entire design in the video after the break has us really loving its features.

He’s using the head from a VCR as the spinning motor. The display itself uses a vertical row of LEDs with a bit of wax paper as a diffuser. These are current limited by a 1k resistor for each of the eight pixels. They’re driven by a PIC 16F690 but you may have already noticed that there’s no battery on the spinning part of the board. It gets voltage and ground from a pair of brushes which he fabricated himself. To avoid having to do the same thing to map the control buttons in the base to the spinning board he came up with something special. There’s a downward facing phototransisor which registers LED signals from the base to move the paddles up or down.

If you love this project check out the POV Death Star.

[Read more...]

HDD POV clock takes the best from those that came before it

hdd-pov-clock

The concept behind this clock has been seen before, but [Dieter] tried to combine the best aspects of several projects into his HDD POV clock (translated). The basic principle of the design is to cut a slot into the top platter of the hard drive. This will let the light from some LEDs shine through. By carefully synchronizing the LED with the spinning platter a set of differently colored hands can be shown to mark time. We’ve been looking at the project for several minutes now and we’re not quite sure if the lines marking the 5-minute segments on the clock are generated in the same way as the hands, or if they’re marks on a faceplate on top of the platters. Check out the clip after the break and let us know what you think.

Past HDD clock project include this one, or this other one. Some of the design improvements include a better motor driver (which [Dieter] pulled from an old VCR) and the inclusion of an RTC chip to keep accurate time without the need to be connected to a computer. We also think it’s a nice touch to sandwich the hardware between two picture frames for a nice finished look.

[Read more...]

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