Nervo Board Alternatives - My Experience.

[Abraham Sleem]

Greetings all.

After not being able to get the Nervo board I took Gael's advice and wired this up with several PCA 9685 boards instead. One in the head, One in each arm, one in the torso, gave each its own I2C address and connected them all to a custom made board that just split the Grd, SCL, SDA, VCC from rPi5 to each board via 2 x 3pin cables (servo extention cords). 

Tried to do V+ in the same cable (as the 6th PIN) and wired it up with a 6.5V battery but it was making too much heat and the servos started to jitter a lot. So went with a separate thicker gauge cable  to the green power jacks on each board. Much better. No heat issues. Smaller servos in the head were burning out from the 6.5V voltage so I got a step down voltage regulator to 5V for that particular PCA9685 . 

[Ray Edgley]

I've been using the PCA9685's in the left and right hands, one on the back and one in the head.
6V for the lot using SMPS dropping the battery voltage from 20V down to 6V
Each arm and the back gets a 20A SMPS each while the head is a 12A SMPS.
I use much heavier wire for the power to each of the PCA9685 and connect these to the power terminals in the middle.
Strong advice here, do not use the +V pin on the end with the control pins, the trace will not carry the current if all the servos run at the same time, the race will burn out.

Ray,

Cyber_One YouTube Channel