4 DIGIT 7 SEGMENT DISPLAY COMMON CATHODE

For a long time we’ve had small 7-segment displays andhuge 7-segment displays, but now we finally have something in between. These 20mm 4-digit 7-segment displays are big enough to see from a distance but not so big that you’d have trouble finding an enclosure for them.
4-digit 7-segment displays are really neat little devices, it's a shame that they can be so cumbersome to control. Well Sparkfun have solved that problem by making them a little bit "smarter." The 7-Segment Serial Display combines a classic 4-digit 7-segment display and an ATMega328 microcontroller allowing you to control every segment individually using only a few serial lines.
The Serial 7-Segment Display can be controlled in one of three ways: Serial TTL communication, SPI serial communication or I2C serial. You can even program it for stand-alone operation since the ATMega328 comes pre-loaded with the Arduino bootloader! There is also an FTDI header on board and Sparfun have provided a hardware profile for the Arduino IDE to make it even easier to program.
These common-cathode displays feature 4 x 7-segment digits and one decimal point per digit. The LEDs have a forward voltage of 1.9VDC and a max forward current of 20mA. Design a clock, timer or counter into your next project using our pretty 4-digit seven-segment display. These bright crisp displays are good for adding numeric output. Besides the four 7-segments, there are decimal points on each digit and an extra wire for colon-dots in the center (good for time-based projects).