Hello there, I’m a beginner and I’m trying to build my first robot (quadruped with 12 servos)with my best friend, he has already built a very nice frame( he builds rc planes), now it’s my turn to make the circuit and to program it. I’m using an Arduino Uno (which I’m familiar with) and an Adafruit PCA9685 16-Channel Servo Driver and HK15138 servos. My intention is to power it with a single 7.4 V 5000mhA Li-po battery that my friend has ( I don’t wanna buy a new battery just for this project) how should I proceed to connect everything together, taking into account the different tolerances of voltage and current of the electronics? For example I know that the Vin pin of the Arduino can take this voltage, but how can I be sure that the board won’t be damaged by the current? Thanks in advance
Hello @ricarlo_milos and welcome to the forum!
I think this tutorial can help you out:
Also, it would be great if you could share the final robot here on the Robots section that way you could participate in the Robot of the Month Contest.
Good luck with your robot!
Thank you, the guide did help me out a bit, but I have still some questions, how do i choose the right type of voltage regulator, and how do I keep the excess current away from the controller? I will be glad to share this robot once it is finished in the Robot of the Month Contest!
I’ve been reading up this time, and I believe that I need a UBEC since a 2s Li-po can reach a voltage quite higher than the nominal voltage.This is to protect the servos. Can somebody confirm that the battery will only supply the needed current and not fry my Arduino?
Hello again @ricarlo_milos
I’m glad the guide helped you a bit 
You could use the battery you mentioned to power the Arduino (don’t need to worry about the current, as long as the voltage is steady and between the limits 7-12V everything will be fine) and use a 5V Voltage Regulator (or the UBEC you mentioned) to power the servo driver (just choose one that can output the current the servos draw)
Also, as motors produce large amounts of noise they could interfere with your Arduino causing it to reset so you might want to consider using some decoupling capacitors. The Adafruit driver you mentioned even has a spot to place a big capacitor on the V+ line. Here’s a guide that could help you out with that:
Thank you @geraldinebc15 , this confirms what I have been figuring out myself while browsing on this forum and the arduino forum .I made up this schematic on Fritzing
, would you be so kind to tell me if it is correct? I really don’t want to mess this up. Just pretend that the battery is 7.4 volts and that there are many servos attached. I really didn’t know that I probably needed some decoupling capacitors, and I will read the helpful guide you sent me tomorrow. I’m very happy that the forum is full of useful information, and that there are helpful moderators like you.
Everything seems good to me!
Just a little tip try to not make diagonal connections.
Try to make them like these next time, that way everything looks cleaner and it is easier to check on it
And if you need more info about the decoupling capacitors here’s some:
You may or may not need them, but they definitely won’t hurt haha
You are very welcome, I’m glad I could help you out 
Ok, got it, was my first time using the program, thank you very much!