Scoreboard

I am building a score board that needs to count till 100. So I will use an UNO with two buttons attached. Button One -> Point for 1st Team, Button Two -> Point for 2nd team. By pressing a button, a little beep should sound and the score should change.
for every segment (7 per digit) there will be 3 leds in series. 3x7x6=126 LEDS. +2LEDS as dots. I will use 5 shift registers to control each group of leds.
The leds use 2.2V and 20ma each. How do I power them?

First of all I'd say you place the LEDs in parallel instead of in series, then they still only need 2.2V, but it will draw 60mA current per segment.
With a bit of logic structuring you could handle all of the segments with 3 shift registers (e.g. 74HC595 or TPIC6B595), since 126+2=128 and 128/8=16.
So make it a multiplexed matrix of 8 rows and 16 cols, or the other way around.

Then you could power them using a FET connected with gate to the output of the shift register, drain to +5V and source to the anodes of the LEDs.
At the at the kathodes of the LEDs, connect gate to the output of the shift register, drain to kathodes and source to GND.

Don't forget to put in resistors for the LEDs at every segment, or better at every connection between kathode and ground, since otherwise you'll blow up your LEDs+FETs, and that's not something we want, is it?

Remember that I am newbie :slight_smile:
So, firstly, you mean charlieplexing?
Secondly, what kind of Fets?
Thirdly, what about the resistors?
Please excuse me, but I am still learning...

So, firstly, you mean charlieplexing?

No.

Heh. Every segment has three LEDs and those 3 LEDs don't need to be individually controlled. So actually there are 42 groups of LEDs plus other two LEDs that will be on continuously. So now if I am not mistaken, I need only two shift registers, or maybe one by using more arduino pins? But what about the Fets? What exactly do they do and what should their specifications be? Additionally, what should the value of each resistor be? Where exactly should the resistors be placed? And, at last, will this configuration need external power supplying? Sorry for asking noob questions...

If it only needs to count to 100, then you can get rid of some LEDs.
This is because the digit on the left will either be blank or "1", so you can get rid of the LEDs that are not part of the "1".