Adding hall sensors to brushless outrunner motors

ArduRover Miscellaneous
1

Hi,

is there anybody here who knows how to do this, which sensors to buy, etc? I would like to use two brushless outrunners with sensored car escs.

2

The encoders mentioned in the wiki are grounded to the Pololu motors but are discontinued for a newer model with endcaps.
New item

You may be able to use https://www.pololu.com/product/3499 and mount to outrunner case. I think those are the highest count per rev. they make. Not sure how fast a rover your making as they do make a few stand alone encoders

3

Thanks for your reply and sorry, I did not make clear enough what I am trying to do. I want to convert two sensorless brushless outrunner motors into sensored brushless motors, to make them start and run smooth at low rpm. I am using blheli ESCs right now and already got them configured quite good, but sometimes, the motors just start to vibrate.
After playing with google search terms, I found a site where the theory of sensor placement gets explained really good:

4

Dear Sebastian,
Have you added the hall sensors? I saw in the wiki, they could add encoders:
http://ardupilot.org/rover/docs/wheel-encoder.html

5

Yes, to two different motors so far. And I also added quadrature encoders.

6

Hi, Sebastian
Which version of Firmware do you use? Could you give me any hints? Thanks

7

Hints regarding what? Quadrature encoders, or commutation sensors?
I am running ardurover 3.5.

8

Hi, Sebastian
My brushless motors has hall sensor, and ESC support it. Should I directly connect the ESC to flight controller? Does the ArduRover 3.5 directly support this or should I develop for it? Thansk

9

If the ESC takes a RC PWM signal, just connect it to the flightcontroller. The hall sensors in the motor have nothing to do with the connection between ESC and flightcontroller.

10

Hi, what’s the role of hall sensor here? Thanks

11

The sensors tell the ESC when to power each set of coils, instead of doing it sensorless, where the ESC has to meassure the backemf to know when to power which set of coils. This does not work while the motor is not turning, so the ESC randomly powers a set of coils to start the motor and then reacts to the backemf it meassures to keep it turning.
This works for airplanes or multirotors, but not so well for cars, where the motor can not rotate freely. If you got a RC race car, the ESC just starts with enough power to get the motor turning, because it is meant to go fast anyways.
For a rover or a RC crawler you want a slow start with a lot of torque and precise speed control, so sensored motors are the way to go.

12

Hi, in the wiki,
http://ardupilot.org/rover/docs/wheel-encoder.html
there are two output A and B of motor encoder, but there are three outputs of my motor hall sensor, could I convert hall signal to encoder signal, then using AP_WheelEncoder library to get the rpm of the motor? Thanks

13

The sensors in the motor output a three phase signal, 120° offset. Quadrature encoders output a 90° offset signal. You would have to use an arduino or similar to convert the signal.
Hall sensors are just the technical means to get the signal. You can use many different sensors to get either signal (quadrature or three phase). Optical, mechanical or, in case of the hall sensors, magnetical.

14

Thanks, Sebastian
I should use arduino to convert the signal and test it!
How is your result using hall senor?
I think I should post my process and results, so you could give more suggestion!
Sincerely

15

My rover is working fine. I added three hall sensors to the bldc aircraft motors for commutation and another to as quadrature encoders.