Will it work if I place hall sensors facing the magnets like in the picture below? I cannot put it in between the teeth because the hall sensor is bigger than the gap.

enter image description here

  • \$\begingroup\$ No. The sensors have to be placed between the winding and magnet so that the flux lines cut through the sensor the right way (look at B-field orientation in the datasheet). The sensor will not work well placed to the side of the winding. They also need to be located so that they transition at the correct time so that commutation will work. That is kind of complicated to explain fully. \$\endgroup\$
    – user57037
    Commented Dec 6, 2017 at 5:42
  • \$\begingroup\$ The problem with placing them off to the side as you show is that the magnetic field there is irregular. The B-field lines are not predictable because it is in the fringe area of the B-field. You will have a hard time running using the Hall sensors and not get full performance from the motor. You need to place the sensors more inside the stator so that the B-field lines are running straight across the airgap between stator and rotor. As mentioned above, the magnetic field must cross the sensor in the direction intended. Look at the datasheet. \$\endgroup\$
    – user57037
    Commented Dec 6, 2017 at 5:46
  • \$\begingroup\$ I'm not well informed about how you'd use hall effect sensors to perform commutation well, but as for the issue of fitting the sensor where you want it, it looks to me like that slot could be cut wider in the right spot with a rotary tool and depth jig. If you end up hitting copper, those windings look pretty sloppy so you can probably hand wind them to equal quality without trouble. \$\endgroup\$
    – K H
    Commented Sep 15, 2018 at 17:26

1 Answer 1


No that will not work. You must sense flux reversal on 3 consecutive windings only and be precisely positioned so starting torque is always positive, otherwise dither or dead spots (stall) will occur.


  • \$\begingroup\$ Hi, I want to add hall sensor inner the motor, not outside the case. \$\endgroup\$
    – complez
    Commented Dec 5, 2017 at 7:55
  • \$\begingroup\$ And your reason is? How will you prevent the problems I answered. Consider tolerances involved to ensure correct commutation and what happens if wrong. i.e. detects position for +torque is still -torque \$\endgroup\$ Commented Dec 5, 2017 at 16:09
  • \$\begingroup\$ @TonyStewart.EEsince'75 my reason is all sensored outrunner motor that selling on market is always has hall sensor inside the motor \$\endgroup\$
    – complez
    Commented Dec 6, 2017 at 1:29
  • \$\begingroup\$ If you can duplicate the micro-tolerances required , minimize flux leakage and manage the conductor path of commercial outrunner designs. great, but there's more too it than gluing in Hall sensors. \$\endgroup\$ Commented Dec 6, 2017 at 2:49
  • \$\begingroup\$ @complez Those sensored outrunners are made to accomodate for that. Sensorless outrunners aren't. Big difference. Different methods for different things. \$\endgroup\$
    – DKNguyen
    Commented Oct 1, 2019 at 4:39

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