PWM, Servos, and the BBB

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1

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.

2

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

http://www.elinux.org/Beagleboard:BeagleBoneBlack#Expansion_Header_Usage

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.

Gerald

3

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.

4

Hi,

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.

Roy