I posted on here the other day with a question about stepper motors, and everybody was super nice and helpful I think the best answer to my question is to use a servo motor instead of a stepper motor (it will also save on space). I'll be heading out tomorrow to buy a servo motor for my project, but I have a question!
I have heard that, for reliability, it would be best to power my servo with an external battery (instead of using the Arduino 5V pin). I already have a battery that will power my Arduino Nano - it's 11.1V. I'm looking to buy a servo that runs comfortably on 5V of power. My question is, do I need a resistor? How do I work out what kind of resistor I need?
I've done a bit of googling, and I've found the V = IR equation. I need 6.1V of voltage drop to get it down to 5V, but how do I work out the current (I)? I've looked up a few 5V servos online, but I can't see anything about the required current on the datasheet.
Maybe I've got this whole thing backwards, and it's more about the battery than the servo itself. Also, is there anybody out there who thinks I should just use the 5V pin on the Arduino instead?
Oh that's great! Thank you
Are they as plug-and-play as they look? I just plug the battery in on one end, send out a positive and a negative wire on the other, connect them to the servo; and it will just work?
Thanks for the reply!
I only saw one person who said not to use the 5V pin, but ALL the servo tutorials I could find, just plugged it in there. Reliability is really important for the project, so I'd much rather do it with a battery if that is a factor.
All electrical signals need a reurn path. So you will always have two wires to transmit a signal.
The PWM signal from the Arduino will also need two wires, one from the digital I/O pin AND one from the ground.
You need a voltage regulator, and make sure it can handle the current (Amps or milliamps) for the motor.
I don't think there are many 5V servos. 6V or more seems to be more common.
...You can make a Voltage Divider with 2 resistors but they are only good for low power "signals" or "reference voltage", not for the power supply. If you try to use a voltage divider for power, the "resistance" of a motor varies with load (most "things" don't have a constant-known resistance) and the series resistor wastes power.
That's a linear regulator but your wiring is correct.
However the buck converter may have an input + and - and an output + and -
So the input +/- connects to the battery and the output +/- connects to he servo.
I think the best answer to my question is to use a servo motor instead of a stepper motor (it will also save on space). I'll be heading out tomorrow to buy a servo motor for my project, but I have a question!
I'm very new to hardware and batteries really freak me out 
