It is always good to have more current capacity. The circuit will use what it needs. You could use a 100000A supply and as long at the output is regulated to 5V (or whatever your mystery Arduino is) it will work fine.
Probably not a good idea to drive a solenoid off the same unregulated supply that feedsthe arduino 5V regulator but you can try it.And the Arduino current max is 800mA @ 5V,which, if you know your Ohms Law is 4W, whichyou should know is only 333mA @ 12V.(do the math: P= I*V)So your load is 1.2A+ 0.333A = 1.533A @12V,NOT 2.5A@12V.Groundfungas knows that but he was probably distracted or had something else on his mind.
You really need to stop and learn Ohm's Law.Then you wouldn't ask such questions.Even with all you extras I doubt you are anywhere close to your 800mA @5V maximum so yes,1.5A would be fine. And as Groundfungas ALREADY told you, thearduino uses shat it needs so why would youask if the 1.2A solenoid would damage the arduinoif the solenoid was not in use. Seriously, if your going to use electronics, at least learn the basics of Source and Load and Ohms Law (P=I*V/V=I*R).
The isn't planning to overload the 5V.All he wants to do is power his solenoid and the uno and few other things from a single12V power supply .
Can you list enough 5V addons to draw 185mA ?As much as it sounds like it's still only a 1/3rd of what it could support.
Nobody's talking about exeeding pin limits.
From what I researched, Arduino can hold up to 7-12V (Total maximum current draw when powered via external power supply: 1A) and I have a 12V solenoid lock around (1.2A). I am planning to connect it in parallel circuit so the voltage will be the same and sum of the currents through each path is equal to the total current that flows from the source.
So here comes the question, if I were to get a adapter of 12V what should my current supply be? If I calculate Arduino max current 1A + Solenoid lock 1.2A, i will have to get around 2A or 2.5A supply. But if I only calculate the Ampere I need, I only need to get 1.5A supply.