4 Digit 7 Segment LED

Basics
CC means Common cathode CA means common anode
Dot matrix module, digital tube, and bars are regularly arranged LED (LED light-emitting diode) products, Generally, colors are red, yellow- green, green, yellow, blue and white.
LEDs normal operating current is generally 1-20mA, the larger the current the higher the brightness. Brightness required, the current in this range.
Different colors of the forward voltage drop (Vf commonly represented) are different, red, yellow - green, yellow is about 1.8V, green, blue, white, about 3.1V, LED parallel drive voltage constant. For large-size digital tube, LED is connected in series, the number must be multiplied by the total pressure drop led series, namely Vf * N, the driving voltage must be greater than the total pressure drop led to light.
Led drive current limiting resistor should be added protection, current limiting resistor R values determined by the following formula:
R = (Vcc-Vf * N) / I, where Vcc is the supply voltage, Vf for the voltage drop, N is the number of LED in series, I bit operating current (unit A, 1A = 1000mA), such as: Vcc = 5V, Vf = 1.8, N = 1, I = 10mA, then R = 320Ohm, available resistor 330Ohm. If the product is blue, Vf = 3.1V, then R = 190ohm. The actual parameter calculation based on operating voltage and current needs.
LED power Pled = Vf * N * I, the current limiting resistor dissipates Pr = I * I * R, for example, the above example: Pled = 1.8 * 1 * 10mA = 18mW, Pr = 10mA * 10mA * 330ohm = 33mW .
The above are single LED computing, such as the simultaneous need lights N pieces of LED, please * N.
The following is a common LED drive circuit (not prohibited limiting resistor test !! avoid burn LED.