Micro Serial Servo Controller VIN vs Servo Supply

I built a six-legged walking robot with 12 servo motors which are controlled with two Pololu Micro Serial Servo Controller.

I am using a regulated 5V Power Supply for everything: all 12 motors, the Pololu Servo Controller and a PIC16F648A to provide the required signals to the Servo Controller and it works just fine, but when I try to use two diferent Power Supplies one for the Servo Controller (5V in the Pins VIN and GND) and another in the servo suply (6V in the pins + and -) I just can’t make it work, I get a red LED ON and a green LED blinking.

I soon as I get back to ONE 5V power supply, everything is ok. If I understood correctly the user manual I can have two diferent power suplies: one for the logic of the servo controller and another for the motors, Am I wrong?

Can anyone help me? All I want is to be able to make my robot work with batteries I am open to any suggestion.

Thank you.



Two batteries should be easier to get working than one battery. I suspect you have some kind of problem in the way your grounds are connected. What is powering your PIC? Perhaps your new 5V source in the 2-battery setup cannot power everything you want it to.

- Jan

Thank you for your reply, Jan. I finally got it to work properly.

No, I did not have anything wrong with the ground between both batteries.

The PIC and the Servo Controller Logic (VIN) are powered from a std 9V battery through a 5V regulator 7805 and few capacitors.
The Servo Motors are powered directly from a 4 cells battery pack.
All grounds are conected together. I am using a 2P2T Switch to conect both suplies.

The way a fixed the problem was sending a reset signal from the PIC to the Servo Controller for about 200 ms and the problem went away.

I guess the problem is that the 7805 IC Regulator provides power little bit later than the 4 1.5V Battery pack, and the Servo Controller may receive some erratic signals although both: PIC and Servo Controller logic (VIN) start receiving power at the same time. I do not Know it just a thought. I may be wrong. What do you think?

The good thing is: it is working just fine.