persistence of vision

62 Articles

Puppy POV: Four-legged Persistence Of Vision Display

June 14, 2011 by 7 Comments

puppy_pov

We see lots of persistence of vision projects around here, but we can’t recall any that involve a POV display facilitated by a living, breathing animal (humans aside, if you want to picky). [Michael] has a Miniature Pinscher that just loves to run and run…and run…in circles. Since she generally runs very fast and in large curves, he thought she would make a great POV device.

He has a small fleece “jacket” for his dog, and on it, he mounted a Lilypad Arduino, the associated power supply, and five bright white LEDs. Naturally, conductive thread was used to wire up the circuit, and after a bit of trial and error, things came together nicely.

With the vest complete, [Michael] unleashed his dog at the park, letting her run to her heart’s content. All the while, her vest was writing out [Cory Doctorow’s] “Makers” while he snapped some pictures.

We can’t think of a more appropriate text to write with LEDs in the night, but in the spirit of the book, we were hoping to see a circuit diagram or the project’s code posted. If he shares it, perhaps we could convince [Cory Doctorow] to run about the park in a vest, writing out [Michael’s] code in bright white LEDs!

A Beginner’s Guide To LED Matrices

April 29, 2011 by 4 Comments

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[Rajendra Bhatt] wrote in to share a tutorial he put together demonstrating the basics of using LED dot matrix displays. While this subject might be old hat to many out there, his helpful walkthroughs are geared more towards beginners who are exploring various electronics concepts for the first time.

He explains the theory behind LED displays using a PIC-driven 5×7 matrix as an example. He discusses persistence of vision and how tricking the human eye can save you quite a bit of time and a whole lot of pins. Multiplexing is broken down into its most basic steps, which [Rajendra] illustrates by showing how a letter would be drawn on the LED display one column at a time. The use of a ULN2803A Darlington Array is also discussed, and he details why it is used when pulling the five columns of LEDs to ground.

The only portion of the tutorial we thought could be expanded upon was the programming section. While he does show how each letter of the alphabet can be displayed via a series of five hex values, he does not cover the “why” part of the process. Obviously while anyone familiar with binary and hex can figure it out in pretty short order, we think that it would be a great place to pause and expand the readers’ knowledge even more.

Overall it’s a useful tutorial, and most beginners would likely find it quite helpful.

Theory Behind Evanescent Wave Coupling, Aka Wireless Power

January 14, 2011 by 30 Comments

[Alan Yates] is building a persistence of vision display and needs a way to transfer power from the stationary base to the spinning circuitry. He’s decided to go with wireless energy transfer and he’s sharing all of his research and experiment data from the development process. It comes in two forms, the written version we just linked to, and a 37 minute video which is embedded after the break. If you liked some of the inductive energy transmission devices we’ve featured in the past, [Alan’s] video will fill you in on the why’s and how’s by using a combination of illustrative schematic examples and measurements on test coils that he built.

Continue reading “Theory Behind Evanescent Wave Coupling, Aka Wireless Power” →

Lots Of Spinning POV Goodness

November 13, 2010 by 19 Comments

[Retrobrad’s] spinning POV display has long been our favorite. When it popped up on our radar again this morning we were surprise to see we never ran a feature on it! But now there’s so much more to share. Hit the projects icon at the top of his page and you’ll not only get the 8×85 RGB display’s build instructions, but he’s also built a 32×64 pixel spinning display.

Even if you’re not going to make one of these, he explains some pixel-graphics techniques that are useful in other instances. Check out his video on using spreadsheets for creating the hex arrays necessary for each frame the 8×85 display. It’s embedded after the break along with demos of the two displays.

Continue reading “Lots Of Spinning POV Goodness” →

Helicopter POV Display Is A Masterwork

November 12, 2010 by 22 Comments

helicopter hack LED mod

Yes! A radio control helicopter with a fairly high-resolution persistence-of-vision display is a beautiful thing. [Mziwisky’s] handiwork is the result of several steps along the prototyping path. He built up a POV test rig on a breadboard, designed his first PCB for the project, and then went to work building it. After initially being inspired by a POV ceiling fan [Mziwisky] looked around to see if anyone else had already added a display to a helicopter. Indeed, this has been done before but there were very few details on the build.

The helicopter has two blades and each have the same hardware on them and gobbled up about ten hours of assembly time each. He basically built a printed circuit board using the blades as a substrate by attaching adhesive copper foil. This makes up the matrix for the LEDs and connects to a small circuit board with an ATmega8 and some shift registers mounted on the inside end of the blade. There’s also a 180 mAh LiPo battery pack, and a hall effect sensor to synchronize the display on each. The results are spectacular, as you can see in the video after the break, but there’s a few bugs left to work out in order to fully tame the 32 LEDs on each rotor.

Kind of looks like the future is happening right now.

Continue reading “Helicopter POV Display Is A Masterwork” →

72 LED Persistence Of Vision Globe

October 15, 2009 by 34 Comments

HaD-pov-globe

[Ben] told us about his POV globe yesterday. We took a look and saw just one photo and the code with no real explanation of his project. He certainly set to work over night and now we see all the goodies we look for in a great build log. He even threw the Hackaday logo up for our enjoyment. His build is well executed and he found some creative ways around the common problems in these projects. We take a closer look after the break. Continue reading “72 LED Persistence Of Vision Globe” →

POV Fan EEPROM Hack

October 9, 2009 by 4 Comments

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Hacking with Gum got their hands on one of the persistence of vision display fans that Cenzic was giving away at Blackhat this year. It’s not the biggest fan-based POV display we’ve seen but it’s still a fun device to tinker with. They hacked into the EEPROM on the device in order to change the message the fan displayed.

This is very similar to the other EEPROM reading/writing we’ve seen recently. Hacking with Gum read the data off of the EEPROM and then disassembled it to discover how the message data is stored on the chip. This was made easier by noting the messages displayed when the fan is running. The first byte of data shows the number of words in the message, then each chunk of word data is preceded by one byte that represents the number of letters in that work. Data length was calculated based on the number of pixels in each display character. Once he knew the data-storage scheme, it was just a matter of formatting his own messages in the same way and overwriting the chip.

This is a great write-up if you’re looking for a primer on reverse engineering an unknown hardware system. If you had fun trying out our barcode challenges perhaps deciphering EEPROM data from a simple device should be your next quest.

[Thanks James]