A POV globe display with 40 RGB LEDs.
On this page I will try to show you the features and how I built it. Please note that this page should not be considered as a step by step tutorial.
Deutsche Beschreibung: auf mikrocontroller.net
Here are just some of the effects I wrote for the globe. Youtube link
Let's start with the rotor. It is made of a 15mm aluminium bar and a 12mm aluminum tube.
The diameter of the rotor is about 200mm, so I cut a fitting slice of wood. The ends should overlap some cm so they can screwed together. I also cut some smaller slices for bending, until the diameter of the rotor after bending was ok and without tension (important because of the 2 holes).
After that, I fit the ring onto the 200mm wood slice and drilled the 12mm holes for the tube. The tube is about 300mm long, just long enough for mounting 2 ball bearings, the controller pcb and the sliding contact.
Both parts were glued together with epoxy.
The LEDs are SMD RGB LEDs (5050,PLCC6), these LEDs are bright and have 3 seperated anodes and cathodes. I used 15 74HC595 shift registers, 5 in series for each color. Each register can take up to 70mA on the Vcc and GND pins, so if I want to drive the LEDs with nearly 20mA I have to connect 4 LEDs common anode and 4 common cathode to each register.
This leads to 2 things: since I reversed the pins this by rotating the LEDs by 180deg, the green and blue pins are flipped. Second, 4 LEDs are active high, 4 are active low. You have to take care of this in the software.
See the rotor schematic (in the .tgz) for the wiring of 8 LEDs, the whole unit is used 5 times and the registers are connected in series (for each color).
The supply and bus lines can be passed through 2 holes inside the tube. After mounting, connecting and testing everything I used a large amount of epoxy to cast everything and make it rugged. Note: SMD resistors would be a better choice.