PWM, Servos, and the BBB

Hi everybody.
I’ve got a Beaglebone Black Rev A6A here, and no matter what I do, I can’t get a servo running. I’ve tried Adafruit’s nice BBIO.PWM library (to no avail) and I’ve tried using Bonescript. I’ve grounded the servo to the BBB, and run 5VDC in from a regulated Elenco supply to the servo. No matter what I do, I can’t get it to turn. If I ground the servo to the power supply’s COM, then it simply whines, no matter the duty cycle. If I ground it to the bone, nothing happens.

Thanks in advance.

Please do not tie a 5VDC servo direct to the pins of the expansion header.

I doubt the servo, one that you have failed to define, can be driven by 6mA,which is the extent of the drive of the 3.3V pins on the board.


I believe you have misunderstood me :slight_smile:
The servo is powered by an external power supply at 5VDC. The signal is from an expansion header. The ground is the same expansion header’s ground.


you need to ground your servo to both grounds. To the BBC ground and your power supply. You need a common ground to make everything work.