Confronted with the issue of finding a use for his mounting pile of junk electronics, [Rue] set out to build a persistence of vision device using a hardware state machine. We have a suspicion that his original link may go down if there’s too much traffic so here’s a cached link just in case.

Any board that is MSC-51 or MCS-48 based would have worked for his purposes. This is because the addressing scheme of the hardware makes it an easy hack. The image above shows him cutting off the processor from this board. It was chosen because of a 74HC373; it was a mistake at first but since it’s pin compatible with the 74HC374 that he needed a simple swap did the trick. From there a clock source was added, and the address information necessary to display the message was burned into an EEPROM.

Step twelve of his writeup shows a Morse Code message created by attaching the board to a broomstick and twirling it around in an arc. We took  just a minute to decode the message and believe it’s a shout-out to Hackaday. Nice, thanks for reading [Rue]!

[Ch00f] spent some serious time figuring out how the Icebreaker POV toy works. This is a pretty cool device about the size of a toothbrush holder. It’s in a clear plastic case, which lets the row of 32 surface mount LEDs shine through. But making light isn’t their only function. You can use the device to scan in a high-contrast design, then ‘play it back’ using the persistence of vision display properties of the LED strip.

Perhaps the biggest question on [Ch00f's] mind was how the sensing is done. He made a series of observations, then started monkeying around with the LEDs to investigate them. It seems that one LED is lit up while the ones around it are used as light sensors. This becomes more confusing once he realized that the display was multiplexed.

His write-up includes a collection of schematics that can be pieced together to conceptualize the entire circuit. The image above was taken during this process, using an LED to check the connections on a part. This let him prove that it’s an N-channel MOSFET. He plans to take what learned and roll it into his own project.

[via Reddit]

A user named [BOcnc] on the rcgroups forums just posted his RGB POV helicopter blades.

The two blades are attached to the heli just as any other whirlygig. The electronics, though, are mounted underneath the blade with a battery pack. We covered a build last year that demonstrated weight added to a spinning blade won’t tear everything apart, but that build used only blue LEDs. This build is full color and makes us feel like we’re living in a cyberpunk future populated by Recognizers and Daft Punk.

The images are stored on an SD card that receives data from a USB port. The microcontroller is a PIC32, and from what we can assume from the schematics, the RPM of the blades is measured by an on-board hall effect sensor (don’t quote us on that, though). There’s no hope of a commercial release from [BOcnc], though. He can’t find anyone to manufacture the blades, and the entire build was too expensive. It sure looks pretty though, so check out the video of it after the break.

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!

[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.

[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.

[via Hacked Gadgets and EEVblog]

[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.

[via Hacked Gadgets]

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.

[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.

[Ben's] design looks much like an actual globe, with a base, a frame, and a rotating ring mounted with its axis tilted (just like the earth). 72 surface mount LEDs are used for the display, a PC fan with the blades removed provides the rotation, and a reed switch in conjunction with a magnet is used to sync the rotation with the display parsing.

Surface mount components are meant to be placed and reflowed on a circuit board. They are usually considered too small for free-form circuits. [Ben] made this process work for him by lining up all 72 LEDs face down on the sticky side of some masking tape. This made it much easier for him to solder together the multiplex needed to interface them with the microcontroller. You can see he is using varnished wire that can be soldered directly without the need for stripping. [Ben's] using a slice of a clear DVD-R container cover as the rotating ring for the display. On the right side of the picture above you can see the completed LED multiplex installed in this transparent ring.

Getting power to the rotating part of a POV display is always an issue to consider. [Ben] tried feeding the connection through a brush motor but had problems with power loss. His next attempt involves using a headphone jack and connector as the pivot point. Regulated power and ground are passed through two of the connections and he’s had great success with this system. Above, you can see the connector before it is fully inserted in the jack on the protoboard.

A reed switch is glued to the transparent ring and is actuated when it passes a bar magnet on the frame. This allows the microcontroller to measure the rotation of the ring, and sync the display output.

[Ben's] done a great job here. He salvaged a lot of the parts, including the LEDs. He’s chosen an Atmel AVR ATmega8 for the microcontroller. This is an inexpensive and readily available chip that is pin compatible with the more powerful ATmega168 so there is a possibility of future upgrade if animations or other functionality are desired, requiring more programming space. We would suggest a decoupling capacitor on the power pins of the uC in order to help filter out any noise on the lines, especially considering the rotating connection used to provide the regulated power.

WE WANT ONE!

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]

[Jon Stanley] has a nice write up on a POV propellor clock powered by a PIC microcontroller. He improved on the original design by [Bob Blick]. Jon tried a few different methods of powering the spinning circuit, some of which could be handy for other projects. As a double plus good bonus, schematics and code are all linked on the site. This clock would look nice and sinister sitting on any mad scientist’s dresser.

Here’s another POV project for you. It’s pretty big, at 1 meter in diameter, not quite as large as the stupidly huge one. What is interesting about this display is that it has a dual motor set up. The original motor didn’t quite have the power to get the display up to the required speed.  A second one was added as the shaft of the rotor. Yes, one motor is actually spinning another motor that is spinning the display. Well, it’s hard to tell from the description. The original motor might be completely unused, but left in place.

[Akeeh] posted something to our flickr pool that caught our eye. The image was a rotating POV display, playing pong. We followed through the links and found this very well done rotating pov display. The construction is quite nice, showing multiple colors and smooth motion. there’s a little bit of wiggle even though it has a custom round pcb. Maybe a little better counter weight would help with that. The idea isn’t new, but it is good looking and elegantly made.

We pretty much don’t know anything about this POV device other than it uses 96 LEDs. We’ve seen POVs with more LEDs, but usually they aren’t packed in so tight. This thing looks almost capable of displaying low res movies. Wouldn’t this thing be cool, and probably dangerous, in a hat?

[via Hacked Gadgets]

[Mario Mauerer] and friends were commissioned to build this 2m persistence of vision display (translated) for a party (in a hight-voltage lab no less). Dubbed “Display from Hell”, it uses 100 blue SMD LEDs to generate the POV images. They’re connected to an ATMega64 via shift registers. Their target speed is 600rpm for a flicker free image, which means the propeller tips are moving at 140mph. The board can be updated wirelessly via IRDA and plans for adding SD storage are in place. You have to see and HEAR this thing in the video embedded below.