persistence of vision

63 Articles

College Project Nets 360 Degree POV Display

July 25, 2019 by 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.

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Persistence Of Vision On An Old Fan

July 23, 2019 by 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” →

A Multi-Layered Spin On Persistence Of Vision

July 20, 2019 by 10 Comments

By taking advantage of persistence in human vision, we can use modest bits of hardware to create an illusion of a far larger display. We’ve featured many POV projects here, but they are almost always an exploration in two dimensions. [Jamal-Ra-Davis] extends that into the third dimension with his Volumetric POV Display.

Having already built a 6x6x6 LED cube, [Jamal] wanted to make it bigger, but was not a fan of the amount of work it would take to grow the size of a three-dimensional array. To sidestep the exponential increase in effort required, he switched to using persistence of vision by spinning the light source and thereby multiplying its effect.

The current version has six arms stacked vertically, each of which presents eight individually addressable APA102 LEDs. When spinning, those 48 LEDs create a 3D display with an effective resolution of 60x8x6.

We saw an earlier iteration of this project a little over a year ago at Bay Area Maker Faire 2018. (A demo video from that evening can be found below.) It was set aside for a while but has now returned to active development as an entry to Hackaday Prize 2019. [Jamal-Ra-Davis] would like to evolve his prototype into something that can be sold as a kit, and all information has been made public so others can build upon this work.

We’ve seen two-dimensional spinning POV LED display in a toy top, and we’ve also seen some POV projects taking steps into the third dimension. We like where this trend is going.

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FlexLED Is A Unique Take On Persistence Of Vision

July 9, 2019 by 13 Comments

Many hackers have experimented with the persistence of vision effect. Whip around a bunch of LEDs, flash them at just the right times, and it’s possible to make images to appear to hang in the air. There’s plenty of ways to do this, whether by manually shaking the LEDs by hand, spinning them around, or even putting them on your bike wheels. [Carl Bugeja] went a different route, taking advantage of the possibilities created by flex PCBs.

[Carl]’s project goes by the name FlexLED. This aptly describes the build, which, in prototype form, mounts a single LED on the end of a flex PCB. The PCB itself has a pattern of traces creating a coil, which enable it to interact with magnetic fields more strongly. By passing the right current through the coil, the flexible PCB can be made to flap up and down, moving the LED on the end at a rapid rate. By then controlling the flashing of the LED, it’s possible to create a persistence of vision effect.

Currently fitted with only one LED, capable of 3 colors, the visual display of the FlexLED is somewhat limited. However, [Carl] reports the effect is more impressive in person than on camera, and is already working on plans to scale up the project to a multi-LED diplay.

POV technology can do some pretty impressive things – even volumetric displays are possible. If you’re working on something yourself, be sure to let us know. Video after the break.

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Star Wars Electrostaff Effect, Done With Spinning LEDs

May 4, 2019 by 11 Comments

[Bithead] wanted to make a prop replica of an Electrostaff from Star Wars, but wasn’t sure how best to create the “crackling arcs of energy” effect at the business ends. After a few false starts, he decided to leverage the persistence of vision effect by spinning LEDs in more than one axis to create helical arcs of light and it seems that this method has some potential.

Many multi-axis persistence of vision devices use a component called a slip ring in order to maintain electrical connections across rotating parts, but [Bithead] had a simpler plan: 3D print a frame and give each axis its own battery. No centralized power source means a quicker prototype without any specialized parts, and therefore a faster proof of concept to test the idea.

[Bithead] already has improvements planned for a new version, but you can see the current prototype in action in the short video embedded after the break.

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Hacker Abroad: Visiting Espressif And Surprising Subway Ads

March 22, 2019 by 17 Comments

Thursday was my final day in Shanghai. After spending all of Wednesday at Electronica Asia, I headed over to the Espressif Headquarters which is just one subway stop away. This is of course the company behind the well-known ESP8266 and its younger sibling, the ESP32. My host was Ivan Grotkothov, Director of Software Platforms. The backstory on how he found his way to the company is truly interesting, as are the stories he shared on some of the legend and lore surrounding the WiFi capable chips the company makes — and the new one whose existence just leaked out this week.

Join me below for that and few other fun things from my last day in this city of 26 million people.

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