Although it appears complex,it is a simple idea and fun very purpose.
- 27 LEDs matte
- Microprocessor ATmega8
- Electrolytic capacitor 47UF 16V
- Small wood board at the minimum 10x10cm
- 50 cm wire tinned
(excuse me, I'm portuguese and my english is not very famous :p)
Step 1: Theory of operation of the array of LEDs
Each LED is turned on a level with a common cathode and each vertical line is connected with a common anode.
So if we want to illuminate a particular LED, just put the level of the 0V line and gave a positive voltage.
To be able to generate an effect of several LEDs on, they have to be powered by multiplexing, a relatively high speed does not seem to be blinking and have a softer light.
As the ATmega8 supports connection of LEDs directly to its pins with a good current, there is no need to put limitation resistors or transistors driver.