I am working on a project with my school's 3D Printing Club where we are making a humanoid robot and I am attempting to wire the arm at the moment, and program the hands to translate text to sign language. The portion of the arm I am currently working with uses six TowerPro 5010 servos, one for each finger, and another for the wrist, and I am controlling it with an Arduino Uno. I have a 9v wall plug that I am powering the Arduino with, and a 4xAA battery pack (wired in series for 6v, last measured at 5.7) that I would like to use for the servos.
Initially, I wired the servo ground pins to the Arduino GND output, and the servo power pins to the battery pack's 6v output, I connected the ground on the battery to the ground on the Arduino, and I attached the servo motors to their IO pins. This approach worked perfectly for two servos, barely for three, and not at all for four. Even with most of the motors staying still (I was only moving one at a time with three and four servos, but I can move two simultaneously no problem with nothing else connected). Not sure how to describe the load on them quantitatively, but they are pulling on fishing line that has a good deal of resistance, but nothing excessive, or near their limits.
I have been googling around for hours, and I found some tutorials where a similar battery was powering eight servos at a time, and so I am unsure why mine was cutting out so soon.
I tried to reduce the load of the servos, but nothing I tried worked. At one point I tried wiring the servos on a shift register to only power the ones I needed, but then I realized this was a dumb idea because my shift register would never be able to output enough current to power even one servo. I have some 5v voltage regulators, but I don't think they will help since the servo takes from 4v to 6v, and I looked through all my transistors, but they are all designed for very small currents. I have a relay which should be able to switch that voltage that voltage easily, but only one of them. If possible I would like to try and do this without purchasing any additional components such as motor controllers or specialized batteries, but I understand that if I need to I need to.
If anyone has any advice on how to proceed I would greatly appreciate it. Thanks.