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Need help with controling ESC with Pi and Servo Hat(PCA9685)


#1

Hello Everyone,

I am working on a project in which I have a Raspberry Pi 3 connected to a servo hat (PCA9685) which is then connected to an RC car. The RC car has ECS which I am sending the signal from the servo hat. Every time I run my code nothing happens and I am not sure why. Does anyone have any suggestions?

additional notes:
I am using the adafruit libraries for the circuityPython PCA9685.
I am using the wiring shown in the doc on page 21:


(Willian Galvani) #2

Can you check the signal with an oscilloscope? That would be ideal.
Another good option is plugging a servo there and checking if it moves (servos DO NEED external power though).
Possible issues are:

  • PWM Signal too low (probably 3.3 V in this setup)
  • Bad ground (unlikely since you are probably powering everything from the same battery)
  • I2C Interface not enabled in raspi-config

#3

Hi Willian,
Unfortunately I do not have an oscilloscope but I was thinking about using an LED to check the PWM; however, I was not sure if I was able to check the PWM from the servo hat. Do you know anything about using servo hats? I have already enabled I2C on the pi. Also I believe the ground is fine because I am able to get the RC car to change the direction of the car now I just need to get the car to move. If the PWM signal is to low what would I need to do to increase it? The servo hat had that it uses up to 6V.


(Jacob) #4

It depends on what ESC is in your car. It might not even take PWM signals or signals in the range that you expect (it probably does, but without a logic analyzer or scope you can’t be sure).

To convert a 3.3V signal to a 5V signal, you need a level shifter.


#5

Hi Jacob,
This is the RC car that I am using:

I want to say that the voltage should be fine becaue I have gotten the car to move once but the code I had was using old libraries and caused other things to break I had to update to the new libraries where the code does not work anymore.


(Patrick José Pereira) #6

Hi,

You should be fine to test it with LEDs, remember that the PCA board has a OE pin, if the problem is with the raspberry GPIO, you can try to put OE in GND and run the example.