3D Zoetrope Uses Illusion To Double The Frames

July 3, 2021 by Kristina Panos 10 Comments

Although film and animation have come quite a long way, there’s still something magical about that grandaddy of them all, the zoetrope. Thanks to persistence of vision, our eyes are fooled into seeing movement where there is none, only carefully laid-out still pictures strobing under the right lighting.

After four months of research, CAD, prototyping, and programming, [Harrison McIntyre] has built a 3D zoetrope that brings a gif to glorious physical life (video, embedded below). All the image pieces are printed and move under a fancy backlight that [Harrison] borrowed from work. It works essentially the same as a 2D zoetrope, as long as you get the spacing juuuuust right. 360° divided by 20 frames comes out to 18° per frame. So a motor spins the disk around, and every 18°, the light pulses for one millisecond and then turns off until the next frame is in position.

The really interesting thing is that there are actually more than 20 frames at play here. If you follow a single character through the loop, it takes 46 frames to complete the animation thanks to something 3D zoetrope pioneer [Kevin Holmes] dubbed ‘animation multiplexing‘, which in [Harrison]’s example, is easily explained as a relay race in which all runners run their section at the same time, creating the illusion of constant motion.

There’s more than one way to use a 3D printer to create a zoetrope, and we doubt we would have ever thought of this one that squashes four dimensions into three.

Continue reading “3D Zoetrope Uses Illusion To Double The Frames” →

Wiggling Screen And DLP Power This Volumetric POV Display

July 1, 2021 by Dan Maloney 25 Comments

It seems like the world is ready for a true 3D display. We’ve seen them in sci-fi for decades now, with the ability to view a scene from any angle and inspect it up close. They’ve remained elusive, but that might just be changing thanks to this open-source persistence-of-vision volumetric display.

If the VVD, as it has been named by its creator [Madaeon], looks somewhat familiar, perhaps it’s because editor-in-chief [Mike Szczys] ran into it back in 2019 at Maker Faire Rome. It looks like it has progressed quite a bit since then, but the basic idea is still the same. A thin, flexible membrane, which is stretched across a frame, is attached to articulated arms. The membrane can move up and down rapidly, fast enough that a 1,000-fps high-speed camera is needed to see it move. That allows you to see the magic in action; a digital light processor (DLP) module projects slices of a 3D image onto the sheet, sending the correct image out for each vertical position of the membrane. Carefully coordinating the images creates the POV illusion of a solid image floating in space, which can be observed from any angle, requires no special glasses, and can even be viewed by groups.

With displays like this, we’re used to issuing the caveat that “it no doubt looks better in person”, but we have to say in the GIFs and videos included the VVD looks pretty darn good. We think this is a natural for inclusion in the 2021 Hackaday Prize, and we’re pleased to see that it made it to the semi-finals of the “Rethink Displays” round.

Big Spinning Disk Makes A Small Color Video Display

June 23, 2021 by Donald Papp 6 Comments

Believe it or not, the Mickey Mouse clip used for this demonstration is actually in the public domain.

The earliest televisions used a spinning disk technology called the Nipkow disk, which is exactly what [Science ‘n’ Stuff] recreated with their Arduino-based mechanical color television (video link, also embedded below.) The device reads video and audio from an SD card, and displays the video using a precisely-timed RGB LED visible through a perforated spinning disk. The persistence of vision effect results in a video that is small, relative to the size of the disk, but perfectly watchable. A twist is that the video is in color!

A Nipkow disk is a fairly simple and electromechanical device that relies on timing; something a modern microcontroller and RGB LED is perfectly capable of delivering. In this device, the holes in the disk create 32 vertical scanlines with 96 “pixels” making up each of those lines. Spinning disk technology was always limited to being monochromatic, but in this implementation, each “pixel” is given its own unique color by adjusting the RGB LED accordingly.

The first video shows off the device and demonstrates it working; note that it may look like there are multiple little screens, but the center one can be thought of as the “true” display with the others essentially being artifacts due to light leakage. If you’re interested in the nuts and bolts of exactly how a Nipkow disk works, then the second video is what you’ll be more interested in, because it goes through all the details of exactly how everything functions.

Another neat thing about Nipkow disks is that image acquisition is really not much more complex than image display.

[via Arduino Blog]

Continue reading “Big Spinning Disk Makes A Small Color Video Display” →

This POV Clock Combines A Nixie With A Pendulum

May 7, 2021 by Dan Maloney 6 Comments

Talk about your mixed timekeeping metaphors: there are clocks, and pendulum clocks, and there are Nixie clocks, and persistence of vision clocks. But this is a Nixie pendulum POV clock, and we think it’s pretty cool.

We first spied this on Twitter and were subsequently pleased to learn that [Jayzon Oeve] has posted a more detailed build log over on Hackaday.io. Rather than a moving array of dots to create the characters to display, this uses a single IN-12b Nixie tube at the end of a pendulum. The pendulum is kept moving by a small nudge created by a pulse through a fixed hard drive voice coil acting on a magnet affixed to the bottom of the pendulum — we’ve seen a similar approach used before.

Pretty much all of the electronics are mounted on the pendulum arm, including a Nano, an RTC, and an accelerometer to figure out where in the swing the bob is and when to flash a number on the display. There’s a video below that shows it at work both at full speed and in slow-motion; as always with POV clocks, these things probably look better in person than on video. And while swinging Nixies around like that seems a little dicey, we like the way this turned out.

Continue reading “This POV Clock Combines A Nixie With A Pendulum” →

Motor-Driven Movement Modernizes POV Toy

February 24, 2021 by Kristina Panos 1 Comment

Just as we are driven today to watch gifs that get better with every loop, people 100+ years ago entertained themselves with various persistence of vision toys that used the power of optical illusions to make still images come to life. [jollifactory] recently recreated one of the first POV devices — the phenakistoscope — into a toy for our times.

The original phenakistoscopes were simple, but the effect they achieved was utterly amazing. Essentially a picture disk with a handle, the user would hold the handle with one hand and spin the disk with the other while looking in a mirror through slits in the disk. Unlike the phenakistoscopes of yore that could only be viewed by one person at a time, this one allows for group watching.

Here’s how it works: an Arduino Nano spins a BLDC motor from an old CD-ROM drive, and two strips of strobing LEDs provide the shutter effect needed to make the pictures look like a moving image.The motor speed is both variable and reversible so the animations can run in both directions.

To make the disks themselves, [jollifactory] printed some original phenakistiscopic artwork and adhered each one to a CD that conveniently snaps onto the motor spindle. Not all of the artwork looks good with a big hole in the middle, so [jollifactory] created a reusable base disk with an anti-slip mat on top to spin those.

If you just want to watch the thing in action, check out the first video below that is all demonstration. There be strobing lights ahead, so consider yourself warned. The second and third videos show [jollifactory] soldering up the custom PCB and building the acrylic stand.

There are plenty of modern ways to build old-fashioned POV toys, from all-digital to all-printable.

Continue reading “Motor-Driven Movement Modernizes POV Toy” →

Proto-TV Tech Lies Behind This POV Clock

February 6, 2021 by Dan Maloney 11 Comments

If it weren’t for persistence of vision, that quirk of biochemically mediated vision, life would be pretty boring. No movies, no TV — nothing but reality, the beauty of nature, and live performances to keep us entertained. Sounds dreadful.

We jest, of course, but POV is behind many cool hacks, one of which is [Joe]’s neat Nipkow disk clock. If you think you’ve never heard of such a thing, you’re probably wrong; Nipkow disks, named after their 19th-century inventor Paul Gottlieb Nipkow, were the central idea behind the earliest attempts at mechanically scanned television. Nipkow disks have a series of evenly spaced, spirally arranged holes that appear to scan across a fixed area when rotated. When placed between a lens and a photosensor, a rudimentary TV camera can be made.

For his Nipkow clock, though, [Joe] turned the idea around and placed a light source behind the rotating disk. Controlling when and what color the LEDs in the array are illuminated relative to the position of the disk determines which pixels are illuminated. [Joe]’s clock uses two LED arrays to double the size of the display area, and a disk with rectangular apertures. The resulting pixels are somewhat keystone-shaped, but it doesn’t really distract from the look of the display. The video below shows the build process and the finished clock in action.

The key to getting the look right in a display like this is the code, and [Joe] put in a considerable effort for his software. If only the early mechanical TV tinkerers had had such help. [Jenny List] did a nice write-up on the early TV pioneers and their Nipkow disk cameras; we’ve also seen other Nipkow displays before, but [Joe]’s clock takes the concept to another level.

Continue reading “Proto-TV Tech Lies Behind This POV Clock” →

Edge-Mounted LEDs Make This Spherical POV Look Fantastic

December 18, 2020 by Dan Maloney 19 Comments

For as many of them as we’ve seen, we still love a good persistence of vision display project. There’s something fascinating about the combination of movement and light creating the illusion of solid surfaces, and there’s always fun to be had in electromechanical aspects of a POV build. This high-resolution spherical POV display pushes all those buttons, and more.

Called “Flicker” for obvious reasons by its creator [Dan Foisy], this POV display started with a pretty clear set of goals in terms of resolution and image quality, plus the need to support animated images, all in a spherical form factor. These goals dictated the final form of the display — a PCB disc spinning vertically. The shaft has the usual slip rings for power distribution and encoders for position feedback. The PCB, though, is where the interesting stuff is.

[Dan] chose to use an FPGA to slice and dice the images, which are fed from a Raspberry Pi’s HDMI port, to the LED drivers. And the LEDs themselves are pretty slick — he found parts with 1.6 mm lead spacing, making them a perfect fit for mounting on the rim of the PCB rather than on either side. A KiCAD script automated the process of laying out the 256 LEDs and their supporting components as evenly as possible, to avoid imbalance issues.

The video below shows Flicker in action — there are a few problem pixels, but on the whole, the display is pretty stunning. We’ve seen a few other spherical POV displays before, but none that look as good as this one does.

Continue reading “Edge-Mounted LEDs Make This Spherical POV Look Fantastic” →