How to use shift register.

Other Hardware General Electronics
4

TPIC6B595 is better for sinking current from LEDs. Works just like 74CH595, but does not have the HC's 70mA total current limit.

Here's the short version of a "tutorial"

digitalWrite (RCLKpin, LOW);
SPI.transfer(fontArray[displayData]); // SCK to SRCLK, MOSI to Ser In, SSpin to SRCK, OE low, MRCLR High
digitalWrite (RCLKpin, HIGH);

byte fontArray[] = {
0b00111111, // 0   DP-g-f-e-d-c-b-a
0b00000110, // 1
etc
0b01101111, // 9
};

Segments:
a
f b
g
e c
d DP