Hello everyone. I've been working on this bot, and I have one problem that I just don't understand. I got it all wired up, but for some reason, it only moves the legs when it's plugged into my pc. It's like it tries to but doesn't have enough power when it isn't. I've got 4aaa batteries wired in parallel to all the servos and to the 5v and ground of the arduino uno.
If you have a multimeter, you can check the voltage to see if it drops when the motors try to run. If you don't have a multimeter, get one! 
In the mean time, you can connect an LED (with an appropriate current-limiting resistor) across the power to the servo. If the LED dims when the motors try to run, the voltage is dropping.
What are the voltage & current ratings for the servos?
I've got 4aaa batteries wired in parallel to all the servos and to the 5v and ground of the arduino uno.
In series or parallel??? In parallel, you'd only get 1.5V but you'd have about 4 times the current available (although batteries shouldn't be used in parallel).
The batteries aren't wired in parallel with the 5V supply, right?
"aaa batteries" are sorta small for such a load. I think you may need larger batteries.
I would use 6XAA in series. I have a few of them. Here is something I would use:
4 AA batteries will run two servos, but not more if all servos are straining at the same time.
DVDdoug:
If you have a multimeter, you can check the voltage to see if it drops when the motors try to run. If you don't have a multimeter, get one!In the mean time, you can connect an LED (with an appropriate current-limiting resistor) across the power to the servo. If the LED dims when the motors try to run, the voltage is dropping.
What are the voltage & current ratings for the servos?
In series or parallel??? In parallel, you'd only get 1.5V but you'd have about 4 times the current available (although batteries shouldn't be used in parallel).The batteries aren't wired in parallel with the 5V supply, right?
Wait, wiring in parallel gives each one 5 volts. It's wiring in a series that shares it's voltage.
The person who originally created the project suggests 4 aaa batteries.
Wait, wiring in parallel gives each one 5 volts. It's wiring in a series that shares it's voltage.
You are confused. Wiring batteries in series adds their voltage, so 4 AA (1.5 V) batteries in series gives about 6 volts, just right for up to two servos.
Instructables are usually nonsense or at best seriously misleading, and the people who post them usually don't even understand what they are doing wrong.
jremington:
You are confused. Wiring batteries in series adds their voltage, so 4 AA (1.5 V) batteries in series gives about 6 volts, just right for up to two servos.Instructables are usually nonsense or at best seriously misleading, and the people who post them usually don't even understand what they are doing wrong.
Oh wait, no I wired the batteries in series. I'm talking about wiring the actual power portion of the servos. So the servos are the ones wired in parallel. Sorry for the confusion. So I should have 6 volts going to every servo.
4 batteries (1.5v each) in series, will provide about 6 volts without a heavy load. Can you measure that with a volt meter? What is it without a load? What is it with both servos running at max. I think aaa batteries are still a bit weak for your needs. Have you looked at 14500 batteries (same size as aa, but 3.7v rechargeable Li-Ion ) ?
Thank you so much! Somehow the batteries must have lost some juice. I used my multimeter, and without anything on, it was only outputting 4 volts. I put new batteries in, and it works!!
Great! glad we could help..