Electronic – Where to place hall sensors (BLDC motor)

brushless-dc-motordc motorhall-effecttiming

I have a BLDC hub motor (out runner type; 3 phase wires) for my electric bike. It currently has 1 set of hall sensors (3 pieces) and I would like to install a second set (3 more) for spare (in case one of the original 3 stops working).

Current hall sensor's locations:
enter image description here
NOTE: on the photo the middle hall sensor is not installed since the photo was taken when replacing it with a new hall sensor.

In the following picture I have tried to indicate which wires serve which purpose:
(The wires indicated in red are the motor phase wires)
enter image description here
The hall sensor-wires indicated in green in the picture go from the outside of the motor (top right in the picture) to the PCB (green circle in the picture) and via traces in the PCB the wires go to the 3 hall sensors.
Color coding:

  • Red, Black = 5V DC
  • Brown = Temp. sensor
  • yellow, orange, blue = sensor signal wires

Photo from slightly different angle:
enter image description here

There is also 1 wire for a temperature sensor among the wires inside the green circle but Its currently not connected.

There are hub motors which come with 2 sets of hall sensors from the factory and I would like to upgrade mine to 2 sets.

The current set was installed from the factory.

I was wondering where I should put the new set of hall sensors in order for the motor's timing (of the different coils) to remain unchanged (in other words so that I don't mess up the motor's timing), both sets of hall sensors have to be activated at the same time such that if i were to connect them in parallel (hall sensor A (set 1) to hall sensor A (set 2) they would only give 1 signal (if that explanation makes any sense).

Is my only option to either place the new hall sensors on top of the existing hall sensors (not sure if i have enough room for this) or to place the new hall sensors on the other side of the motor (current set of hall sensors are placed on top of the windings on the right side of the bicycle (when the motor is inserted), I could perhaps place the new set of hall sensors on top of the windings on the left side of the bicycle. (if you look at the photo I'd want to place them in the same location but on the side of the windings that is currently laying on the table (on the green cloth)).
Any other (better) suggestions for placement of second set of hall sensors are definitely welcome.

Best Answer

You can place the other three Hall sensor in the next groove: That is: you rotate each Hall sensor (clockwise or counter colckwise doesn't matter).

The Hall sensors are needed to detect the commutation instant. The important thing is that the sequence be maintained, so the relative position and not the absolute position is the important thing.