Hey all, I've long been wanting to tinker with Arduino and after year finale got the stuff! I'm making a date clock (ordinal date its a thing) and have 5 large 12v seven segment displays I want to control. I figured out the pin out after discovering these cheap Chinese segments were not the standard pinout and need to figure out how to power, and control them. I don't need the decimals so thats five less pins. But basically its 35 pins at 12 volts. Super new to this so any help would be awesome!
So how did a 7 segment become a 4 segment?
But okay, what did you try? Multiplexing would be the "normal" way of doing it.
1 segment with 8 pins, two are common ground, one I don't need for the decimal. Five pins per segment times 5 segments is 25 total. Im tired, my math was off 
A 7-segment digit with a decimal point needs at least 9 wires...
Most of the time it's something like
Maybe you can draw / tell how your display works?
I just made this for my future reference for the FJS23101AH seven segment display. And I was correct the first time, 7 signal lines for one display (G,F,A,B,E,D,C) times 5 displays is 35 total 12v lines that need to be controlled.
therightprice69:
And I was correct the first time [...]
THe total in the text, yeah. Title, no 
But are you sure they are 12V or they just have 6 LED's in series per side? You can probably count them on low brightness. If there are 6, you probably want to add current regulation.
Next, just look up multiplexing. And for the segments you will need a high side driver (maybe with current regulation). For the low side a simple NPN/N-mos will do.