What power adapter should i use


I am making a project with max7219 displays and i want to power them up. As i understanded correctly better choice is to use power adapter instead of USB from pc.
What power adapter should i use?


What power adapter should i use?

Use one that supplies at least the current you need at the voltage you need. As you haven't told us either then you work it out.

You supply the external power supply.
You supply only 6V to 12V and 2Amp.
You use 12V 2Amp power adapter.

No you don't. You try to avoid 12volt supplies for 5volt logic, especially when linear voltage regulation is used.
Then you always use the minimum voltage needed to get the job done, to minimise power loss (hot parts).

A 5volt cellphone charger connected to the USB socket could be a good choice.
But we won't know until OP states his/her current needs, and the type of Arduino used.

I want to powerup 8 max7219 matrix's.
Soo i am not sure should what kind of adapter should i use, because maybe 5V wont be enought.

Since all you are powering are the displays (no Arduino listed) then:

Step 1: Look up the MAX7219 datasheet to find worst case current. In this case they only provide typical 500mA each.
Step 2: Multiply by 8, to get 4.0A
Step 3: Find a 5V 4A (minimum) power supply.

Thank you.
But i want to powerup arduino too, because how it will get the sketch?
But as i got it i will always need a 5V adapter, its just all about the Amps?

You didn't say the Arduino too. Which one? UNO runs about 300mA, but can't accept 5V (7-12v, the lower the better, 7V is an odd vaue, look for 12V 1/2A).

Anything else need power too?

IMHO, at this current, fuses are useful to prevent creating a lot of smoke.

I measured the displays pictured in post#4 once, and I got ~160mA each, full brightness, all 64 LEDs.
But that might be different from the one you have.
You can estimate current draw by looking at the value of the current limiting resistor on the MAX7219 board.
Then work it out with the datasheet. Or simply measure it...

Four blocks, with just scrolling text, are just ok on an Uno on USB supply.
More, and you need to power the displays separately with a 5volt supply.