Hall Sensor problem

1

Hello Everyone,

I found a strange problem during testing the BLDC motors having in build hall sensor. My setup is a 52 W bldc motor having 4 pp, motor driver DRV8302, and ESP 32 microcontroller.

In a torque control mode when I give a target voltage of 3-4 Volts the output from the hall sensor is ok as shown below :

Hall-1
Hall-11920×1034 109 KB

but if any other target voltage value is given this is the noise introduced or it seems that it skips interrupting i.e not detecting hall sensor value:

Hall-2
Hall-21920×1040 135 KB

I have already introduced the pull-up resistors and by changing the resistor value the result remains the same. Can anyone advise me on how I can solve this issue?

" In the figure, the red is the value from the sensor. get velocity() while blue is the filtered one "

Thanks

2

Might be related to this Motor stops due to direction change - voltages NaN · Issue #192 · simplefoc/Arduino-FOC · GitHub

The title is missleading - it’s an issue with hall sensors randomly readings abnormal values

3

Thanks for your reply, but in my case the motor doesn’t stop while changing direction it’s just that hall sensor is skipping the interrupt.

4

You are right - you are hitting the following case - I don’t know why.

float HallSensor::getVelocity(){
  if (pulse_diff == 0 || ((long)(_micros() - pulse_timestamp) > pulse_diff) ) { // last velocity isn't accurate if too old
    return 0;
  } else {
5

If anyone else finds a similar problem. I solved it by multiplying the pulse_diff by 2.
Change this line in the Hall sensor. cpp file

if (pulse_diff == 0 || ((long)(_micros() - pulse_timestamp) > pulse_diff * 2 ) )

now hall sensor data doesn’t drop to zero during motion.

thanks

1 Like
6

Hi @MoidKhan , and @Aleksandar_Markovic,
Have you tried this to see what is going on ?

To put inside HallSensor.h section private:
// velocity calculation variables
        float angle_prev=0.0f; //!< angle in previous velocity calculation step
        long velocity_calc_timestamp=0; //!< last velocity calculation timestamp

To put inside HallSensor.cpp :

// get current angular velocity (rad/s)
float HallSensor::getVelocity(){
    float Ts;
    // calculate sample time
    unsigned long now_us = _micros();
    
    if(now_us > velocity_calc_timestamp)
      Ts = (now_us - velocity_calc_timestamp)*1e-6;
    else
      Ts = ((0xFFFFFFFF - velocity_calc_timestamp) + now_us)*1e-6;
   
    // current angle
    float angle_c = getAngle();
    // velocity calculation
    float vel = (angle_c - angle_prev)/Ts;
    
    // save variables for future pass
    angle_prev = angle_c;
    velocity_calc_timestamp = now_us;
    return vel;
}
7

No, I haven’t tried this.