POV LED Staff Takes Art For A Spin

October 25, 2020 by Kristina Panos 9 Comments

The human body does plenty of cool tricks, but one of the easiest to take advantage of is persistence of vision (POV). Our eyes continue to see light for a fraction of a second after the light goes off, and we can leverage this into fun blinkenlight toys like POV staffs. Sure, you can buy POV staffs and other devices, but they’re pretty expensive and you won’t learn anything that way. Building something yourself is often the more expensive route, but that’s not the case with [shurik179]’s excellent open-source POV staff.

There’s a lot to like about this project, starting with the detailed instructions. It’s based on the ItsyBitsyM4 Express and Adafruit’s Dotstar LED strips. You could use the Bluetooth version, but it’s already quite easy to load images to the staff because it shows up as a USB mass storage device. We like that [shurik179] added an IMU and coded the staff so that the images look consistent no matter how fast the staff is spinning. In the future, [shurik179] might make a Bluetooth version that’s collapsible. That sounds like quite the feat, and we can’t wait to see it in action.

As cool as it is to wave a POV staff around, there’s no real practical application. What’s more practical than a clock?

3D POV Display Has The Shakes

September 12, 2020 by Danie Conradie 6 Comments

Persistence of vision projects are a dime a dozen, but by adding a third dimension [Madaeon] succesfully created one to stand out from the crowd. Instead of waving around a single line of LEDs, he is moving a 2D grid of them vertically to create a volumetric POV display.

The display consists of oscillating 3D printed piston, powered by a small geared motor, on top of which sits a 8 x 8 RGB LED grid and diffusing film. The motor drives a cylindrical cam, which moves a piston that sits over it, while an optical end stop detects the bottom of the piston’s travel to keep the timing correct. [Madaeon] has not added his code to the project page, but the 3D files for the mechanics are available. The current version creates a lot of vibration, but he plans to improve it by borrowing one of [Karl Bugeja]’s ideas, and using flexible PCBs and magnets.

He also links another very cool volumetric display that he constructed a few years ago. It works by projecting images from a small DLP projector onto an oscillating piece of fabric, to created some surprisingly high definition images.

POV displays are good projects for learning, so if you want to build your own, take a look a simple POV business card, or this well-documented POV spinning top.

Abused Hard Drive Becomes POV Clock

August 14, 2020 by Dan Maloney 7 Comments

We all know that there’s not much to do with an old hard drive. Once you render the platters unreadable and perhaps harvest those powerful magnets, there’s not much left of interest. Unless, of course, you turn the whole thing into a persistence-of-vision clock.

At least that’s what [Leo] did when he created “PendoLux”. The clock itself is pretty simple; like any POV project, it just requires a way to move an array of flashing LEDs back and forth rapidly enough that they can trick the eye into seeing a solid image. [Leo] put the read head mechanism of an old HDD into use for that, after stripping the platters and motor out of it first.

The voice coil and magnet of the head arm are left intact, while a 3D-printed arm carrying seven RGB LEDs replaces the old heads. [Leo] added a small spring to return the arm to a neutral position, and used an Arduino to drive the coil and flash the LEDs. Getting the timing just right was a matter of trial and error; he also needed to eschew the standard LED libraries because of his heavy use of interrupts and used direct addressing instead.

POV clocks may have dropped out of style lately — this hard drive POV clock and a CD-ROM version were posted years ago. But [Leo]’s clock is pretty good looking even for a work in progress, so maybe the style will be making a comeback.

Continue reading “Abused Hard Drive Becomes POV Clock” →

The Basics Of Persistence Of Vision Projects

October 29, 2019 by Lewin Day 6 Comments

Persistence of Vision (POV) is a curious part of the human visual system. It’s the effect by which the perception of an image lingers after light has stopped entering the eye. It’s why a spinning propeller appears as a disc, and why a burning sparkler appears to leave a trail in the air. It’s also commonly used as a display technology, where a series of flashing LEDs can be used to create messages that appear to float in the air. POV displays are a popular microcontroller project, and today, we’ll explore the basic techniques and skills required in such builds.

Continue reading “The Basics Of Persistence Of Vision Projects” →

Kinetic Lamp Sheds Light On Scientific Principles

September 5, 2019 by Kristina Panos 7 Comments

This thing right here might be the coolest desk toy since Newton’s Cradle. It’s [Stephen Co]’s latest installment in a line of mesmerizing, zodiac-themed art lamps that started with the water-dancing Aquarius. All at once, it demonstrates standing waves, persistence of vision, and the stroboscopic effect. And the best part? You can stick your finger in it.

This intriguing lamp is designed to illustrate Pisces, that mythological pair of fish bound by string that represent Aphrodite and her son Eros’ escape from the clutches of Typhon. Here’s what is happening: two 5V DC motors, one running in reverse, are rotating a string at high speeds. The strobing LEDs turn the string into an array of optical illusions depending on the strobing rate, which is controlled with a potentiometer. A second pot sweeps through eleven preset patterns that vary the colors and visual effect. And of course, poking the string will cause interesting interruptions.

The stroboscopic effect hinges on the choice of LED. Those old standby 2812s don’t have a high enough max refresh rate, so [Stephen] sprung for APA102Cs, aka DotStars. Everything is controlled with an Arduino Nano clone. [Stephen] has an active Kickstarter campaign going for Pisces, and one of the rewards is the code and STL files. On the IO page for Pisces, [Stephen] walks us through the cost vs. consumer pricing breakdown.

We love all kinds of lamps around here, from the super-useful to the super-animated.

College Project Nets 360 Degree POV Display

July 25, 2019 by Lewin Day 14 Comments

Senior college projects are the culmination of years of theoretical learning finally put into practice. For many students they are their first experience of doing some proper, real world engineering. [Melangeaddict] chose to take on a persistence of vision display for his final project, and learned plenty along the way.

The display consists of a row of 48 RGB LEDs mounted on an arm capable of rotating a full 360 degrees, with a simple paper diffuser. This arm is spun up by a belt drive from an electric motor at significant rotational speed, so getting close to this machine is quite inadvisable. Thanks to quality bearings and a careful build, rotating resistance is minimal. An infrared LED is mounted on the frame, and the light picked up by a photodiode on the rotating arm, allowing the images to remain fixed in space without drifting over time. Images can be loaded to the display wirelessly over a Bluetooth interface, which was quite advanced for a DIY project in 2011.

We’re a fan of the 360 degree approach to POV displays, and with the right rotational speed and fast data rates, it would be possible to get some seriously high resolution out of the device. Just be careful not to stick your hands in the mechanism.

There’s a deep well to explore when it comes to POV displays, from three-dimensional builds to vibrating flexible setups. Video after the break.

Continue reading “College Project Nets 360 Degree POV Display” →

Persistence Of Vision On An Old Fan

July 23, 2019 by Lewin Day 8 Comments

Persistence of vision is a fun feature of the human visual system, which allows us to blink a bunch of spinning LEDs at the right time to spell out messages that appear to hang in the air. [TN_Inventor] took a stab at his own POV build, using an old desk fan as a base.

The initial build relied on a rotor made of MDF and some very old-school LEDs. The rotor was heavy and unbalanced, causing issues for the motor, and the dim LEDs weren’t visible in normal daytime conditions. Like any good maker, [TN_Inventor] persevered and iterated the design.

The next revision instead relied on protoboard itself for the rotor, greatly reducing the weight and making it easier to balance. The problem of getting power to a rotating mechanism was sidestepped entirely, with a small lipo battery being mounted on the rotor itself. High-brightness white LEDs were employed, making the effect much more visible. This was helped further thanks to the use of transistors to run the LEDs directly from battery voltage, rather than obeying the current limits of the Arduino Nano’s output pins.

The build presents well, with the final POV board being built into the chassis of an old desk fan. Rather than use the original motor, instead a smaller 12 volt geared device was used, powered separately from the main board. The familiar form factor of the desk fan is a great way to finish the project off, and gives it an interesting industrial aesthetic.

POV builds can go a long way – we’ve even seen volumetric displays built in this way. Video after the break. Continue reading “Persistence Of Vision On An Old Fan” →