Controling 4 LED displays with arduino

So I have found 4 Kingbrights LED displays somewhre. Datasheet: http://www.kingbright.com/manager/upload/pdf/SA23-12SRWA(Ver1189473246.9)

The question is how can I control the displays using arduino. Because arduino doesn't have enough pins to do that.

At most, you need eight pins (assuming you need a decimal point) plus 1 pin for each display, making a total of twelve pins. Most arduinos can manage twelve output pins.

Google "Arduino" "seven segment", "multiplex"

Getting clever, you could probably do it with seven pins and charlieplexing.

I googled something like that before - withput multiplexing part. But only thing useful is this: http://picnote.blogspot.com/2008/12/led-7-segment-multiplexing.html

Try and google:- "arduino 7 segment display"

I came up with tons of hits just now.

Great! That helped! I need to improve my googling skills. http://flakblaster.org/?p=131

Now another problem - this is quite large display and the datasheet indicates that one segment needs 7.4V to operate. And that probably means that I will need some outside power source or something? And I noticed that this thing is common anode - so that means that the common pin has to be connected to + and I can light the display with LOW value? Or is this a little more complicated? The four displays that I have are already connected like the schematic there so I will need less work.

o that means that the common pin has to be connected to + and I can light the display with LOW value?

Yes, you would probably be better off doing this with a Darlington array like the ULN2003 or the ULN2803 if you want to include the decimal point. This will also allow you to connect the common anode to the higher voltage and still have it switch with the Arduino.

For now I don’t realy want to buy new components (I buy them when I need many different things not just a resistor or two). So is it possible to connect this to outside power source and control it with arduino without using that IC? On the board with this displays there is some Atmel microcontroller and many transistors so probaly something like this is how it worked before. But I know that sometihng isn’t working - just don’t know what.

So is it possible to connect this to outside power source and control it with arduino without using that IC?

Probably but if you don't know what you have you won't know what to do.