I skipped talking about the sensor part. Here it is:
(Lots of thanks to Shane for explaining this to me and creating the diagrams below.)
Hall effect sensors are glued in between the stator teeth and they detect the pole orientation of the rotor magnets as the rotor spins. The magnets alternate N-S-N-S etc, so each sensor should be outputting some kind of square wave. The controller wants to see the three sensor output signals with 120 deg phase shifts. So, where should we put them?
The figure below shows half the magnets and motor windings in my motor. The first 3 arrows on the left represent 3 hall sensor positions that would generate the correctly phase shifted signals. However, two of them do not represent practical places to actually put the sensors on the stator. So the other blue and red arrows to the right are where we will put them.
For reference, this is what a 12 tooth, 14 magnet sensor layout would look like:
By flipping the hall sensor to face in instead of out, you can come up with other configurations (look at the blue arrows).
I wired up my hall sensors and then supper glued them between the stator teeth.
To actually hook the motor + sensors up to the controller takes some guess and check. I think a good way to go about it is to remember the order of the sensor wires (black – blue – red according to the picture above) and solder them in that sequence to the connector that will plug into the controller. I think this will make it so that they are either correct or “backwards”, which is something you can just fix by changing how the motor phases connect to the controller. After the sensors are hooked up, you just have to try all the combinations of the motor phases to see which one is right.