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Short description: my steering servo goes into full (right) lock when my system is wired in the following way:

  • Pi provides power to the breakout board
  • ESC with BEC is used to provide power to the breakout board for the servo(s)
  • steering servo is connected to breakout board with GND, V+ and PWM
  • ESC "back" connection is only PWM

This is also depicted in the image below, as best as I could.

By "lock" I mean: it goes fully right, and I'm unable to move it at all.

Question is: Is the wiring explained correct (i.e. should it work)?

  • If yes: what would possibly explain the behaviour of the servo?

  • If no: what would the proper wiring look like to provide power from the BEC to the servo?

Longer version: I'm trying to get rid of a multi adapter solution for providing power to my steering servo. Up until now, I've been using a smartphone powerbank, an USB -> 2.5mm barrel adapter (male), 2.5mm barrel (female) -> terminal block, which then connects to the breakout board's terminal block. This works fine, so the servo isn't generally broken.

The DonkeyCar docs mention that it should be possible to power the steering servo via BEC, and they also provide a diagram which connects V+ from BEC directly to the steering servo. This, however, does not work for me - the servo goes into full steering lock as soon as the battery is powered on (and thus the ESC).

The solution provided in the adafruit forums, which mentions that GND and V+ is inter-connected for the entire rail, and that I should be able to simply attach the entire header from the BEC to the breakout board (i.e. V+, GND, PWM) which should then power the servo doesn't work either - with the same issue, it goes into full steering lock.

What I've been trying last is connecting V+ and GND from the BEC directly to the terminal block of the breakout board, connecting only PWM back to the BEC's cable. This also fails, for the exact same reason as above.

I'm pretty much at my wits end here, as I also don't quite get what I'm doing wrong. Note: as of now, I do NOT own a multimeter, so I can't provide any measurements of my own hand have to believe what a datasheet is saying.

If you need any more details, please let me know and I'll be sure to provide what I can. Thanks in advance for any helpful idea, solution, or simply a hint in the right direction.

Parts used:

  • RPi 3 / Jetson Nano

  • PCA9865 breakout board

  • Tamiya TBLE-02S ESC /w BEC
  • Carson steering servo

Note: I've also read other questions, like e.g. about erratic movement, however my servo doesn't behave that way right now - it doesn't work, even for a brief period, and movement is not erratic but fully locked.

servo / motor wiring via BEC

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  • $\begingroup$ @jsotola Thanks, you're right - should have been more clear about this. I've updated my post accordingly. $\endgroup$ – exxe May 30 at 10:07

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