Arduino program to use Hall Effect Sensor stop BLDC motor at the same position every time

Question

I have a set up which consists of a BLDC Motor attached to a gear, a piece of magnet attached on the surface of the gear, hall effect sensor 1mm - 2mm away from the surface of the gear, an ESC connected to the Motor, a receiver and lastly Arduino board that is connected to the ESC, receiver and the hall effect sensor. Below is an illustration of the connection set up. What I hope to achieve is whenever I kill the throttle on the transmitter, the BLDC motor will stop at the position where the magnet is directly under the hall effect sensor. If the magnet cannot brake in time and passes the sensor then the BLDC motor will turn another round at low speed to stop the magnet at the sensor.

What I managed to do at this moment, is calibrate ESC through Arduino and also to brake immediately when the magnet reached the sensor after I kill the throttle. However, I cannot get the magnet to stop directly below the hall sensor. There is a way where I can use hall effect sensor to achieve what I want? Anyone have any suggestion or solutions that is helpful? Appreciate it!

The hardware I am using are,

BLDC Motor - MYSTERY F2520-4800 4800rpm/v RC Helicopter Outrunner Brushless Motor
ESC - DUALSKY XC2512BA 25A 2-4S BRUSHLESS ESC V2
Battery - ZIPPY Compact 1300mAh 2S 25C Lipo Pack
Receiver & Transmitter - Futaba R3006SB & T6K
Arduino - currently I am using Arduino Nano, but I have Uno & Mini as well

Answer 1

You can use a second hall effect 180 degres apart for indicating to the arduino that has to go in slow speed until reach the main position hall sensor, or maybe counting the time after the hall sensor is activated every turn of the motor, so when you cutoff the throttle the arduino knows the time that has spent from the sensor is activated and calculate the offset position to start going in slow speed before reach the sensor.