I understand the idea pos+ to pos+ an ground to arduino ground but my question is if lets say theres 3 servos rated a 6v max now would i need to a power source with a rating of 18v cuz of 3 servos at 6v each?
Like, really no, no.
This is the time to take your servo, set them aside and hit the googles.
You would be well served by searching the following terms:
The Arduino has all of the 5V sources in parallel which means that the current (amps) is split, not the voltage. If you used an 18V source then they would explode which is why Chris is telling you to put them down for now and do some research.
So to answer your question you need just a 6V source if you wire them in parallel (which is what will happen if you go through the Arduino) and you just have to make sure that it has ample current.
But I do still recommend that you do the googling that Chris has suggested. It will help a lot and possibly save you a few dollars (or whatever your currency is) in servos and burnt out ICs.
Ok so I think i got it eventho i find it irrelevant now. 6.4/.4 = 16. I think. it could have been as easy as NO just use 6v.
you need to understand why you need to use 6V. As I said, it will save you money from problems that you may have down the line.
I think I can maybe hone this in for you a bit here.... This is current vs. volts and parallel vs. series here.
And once again, I HIGHLY recommend hitting the googles for this one (parallel vs series), there are exaclty 4.7 billion tutorials on this out there.
Here are the high points.