When working with more complex Ardiuno projects you may find that there isn't enough SRAM - the memory used for storing and manipulating variables when a sketch is running. A typical Arduino board such as the Uno only has two kilobytes, which can run out quickly. Of course there is the internal EEPROM, however this is slower and has a finite life. Australian Nick Gammon has described a way to use additional, external SRAM ICs via the SPI bus with an Arduino to increase the temporary memory that is simple and inexpensive.
For more information an Nick's detailed tutorial, visit his site here. And for more news, updates and items of interest.please follow us on twitter, Facebook and Google+. Another way to increase all three memories of an Arduino (SRAM, flash memory and EEPROM) is to upgrade your project to the Arduino Mega2560:
Not only does the Mega2560 have 54 digital and 16 analog input pins, it has eight kilobytes of SRAM, as well as 256 kilobytes of flash memory. Therefore by using a Mega2560 - you have more sketch room, more variable space, and a bucketload of I/O.