MAX7219 Dot Matrix Module
MAX7219 is a kind of integrated serial input/output common cathode display drive, it connects the microprocessor with the eight-digit seven-segment digital LED display, also can connect the line graph display or 64 independent LEDs. It includes a piece of type B BCD coder, multiplexing scanning circuit, drive period of a word, but also an 8 * 8 static RAM is used to store each data. Only an external register used to set the period of a current of each LED.
A convenient four-wire serial interface can join all general microprocessor. Each data can be addressed in the update does not need to rewrite all the display. MAX7219 also allows users to each data selection code or code.
Arduino L293D motor control shield 
Arduino Ethernet Shield w/MicroSD Card Reader 
315MHZ RF Wireless Module 
Arduino Mega 2560 Board 
Hall Sensor Magnetic Switches