Large 25×25 LED sign board
Description:
Bright LEDs are cheap today. So many new projects with large amount of LEDs can be done. But there is one problem - large amount of LEDs consume large amount of energy. This is a project that implements special technique that allows driving efficiently hundreds of LEDs. This is a large PCB where 25×25 (625 total) LED grid is soldered. Resistors and transistors are positioned around the edges of message board. That entire grid is controlled by AVR micro controller. Displaying technique works as follows: micro controller scans all display row by row through multiplexer. Scanning speed is fast enough to see all non flickering images.
Micro controller:
ATmega164P
For more details click:
http://www.evilmadscientist.com/article.php/peggy