LEGO POV Display (a.k.a. Whizzi-thing)

POV - Persistence of Vision

We initially named our project `Volumetric display' since it displays graphics on to the surface of a cyclinder. This name caused some confusion, so we will now use the more accurate name, Lego POV display, where POV refers to Persistence of Vision. I got the idea after seeing Rickard's mechanically scanned game system.

The general idea is that flat, motionless displays are both boring and expensive because you need hundreds of ... something ... to emit light and produce an image. Instead, use a column of LED's, and move them quickly across your viewing plane (relying on the relatively low sensitivity of the eye to changes in intensity).

Though Rickard's display is cool, we wanted to differentiate our Whizzy machine from those that already exist. With limited engineering resources, and relatively amaturish electronics skills, we had to think of something pretty great. You'll have to wait to find out what that is because our machine is not yet finished - take a look at our prototype in development.

Lots of LED's on a spinning arm

Well, the first stage was hooking up a load of LED's onto a spinning arm, and trying to power them. The image below shows some LED's connected directly to power (without a microprocessor or even a noise reducing capacitor). You can see that our rotating metal washer brushed contacts are far from ideal - a fat capacitor will probably give us a stable enough power source, but there is no way we're going to be able to get data over this!

Test Image 1

Mechanically scanned test image

okay, more electronics are on board. Though "Hello World" is traditional, we're not quite at that stage yet, so use a binary counting sequence instead

Test Image 1
Test Image 2
Test Image 3

Yes... the machine is made from LEGO!

A still image giving away the machines LEGO construction.

The machine

We have a boot screen plus a second colour!

Work on developing the onboard PICs buffering system allows us to hard-code an image as a 'boot screen'

Boot Screen

More Progress... Loading arbitrary images over bluetooth

More work on software both PIC side, and controller side enable us to send arbitrary images over bluetooth (we abandened a physical wire comms approach for radio due to lack of engineering resources).


More Progress... Full Font rasterization!

Using the Freetype2 open source library for font rasterization, the machine can now display fully rendered text in any font, at any size and at any angle.


Two ticks later, and we can scroll arbitrary length text accross our display.

For the same reason that videoing a TV produces streaks accross the recorded image, it is difficult to capture the POV Display in its full glory using a standard video camera. Watch the following video by all means, but please appreciate that aliasing effects trash the illusion...

Hello IBM (I was working there at the time)...

And, being MQTT enabled, it was a sinch to plumb text from my MQTT Windows Media Player Publisher to the display. The Result? Well, if you can hear the music over the whurring of the LEGO arm, the POV Display will let you know what album and artist you're listening to!

Brought to you by Brenton Bailey and myself!

Other Mechanically scanned / POV / Whizzy displays

If you liked that...

If you liked that, check out our DIY Laser Scanner or MQTT Automatic LEGO Rubber Band Gun.


by Steven Lovegrove, Brenton Bailey Jump to top