BAC-028x Controller with failed Hall Sensors

[0037]

I was wondering how the BAC-028x controllers work with failed hall sensors.
I'm having repeated hall sensor failures and want to get this controller so I
don't have to keep replacing the hall sensors.

Q. Apart from having to pedal the bike first to get the motor moving, are there
any other limits, such as a limit to motor top speed?  Can the motor function
as normal with absolutely no hall sensor input?

Q. When a failure occurs is there anything that is needed to be done other
than start pedalling first to get the motor to work?

I would like to use this controller with only the battery, throttle, and phase
wires connected.  Would I encounter any problems?

[e-lmer]

It seems unusual to have repeated hall sensor failures.

The hall effect is such that a current running in
a conductor is deflected by a magnetic field so that
one side of the conductor has a higher voltage than
the other.

It means that there are no moving parts.

Aren't the the only ways to fail to be displaced
physically, or to have heinous current levels because
of a bad controller?

[muzza.au]

G'day,

Here's some info about the difference between running a BLDC motor with and without hall sensors.

In a Brushed DC motor, commutation is controlled by brush position. In a BLDC motor, however, commutation is controlled by the supporting circuitry. The rotor's position must therefore be fed back to the supporting circuitry to enable proper commutation.

Two different techniques can be used to determinerotor position:
• Hall Sensor-based commutation–In the Hall sensor technique, three Hall sensors are placed inside the motor, spaced 120 degrees apart. Each Hall sensor provides either a High or Low output based on the polarity of magnetic pole close to it. Rotor position is determined by analyzing the outputs of all three Hall sensors. Based on the output from hall sensors, the voltages to the motor's three phases are switched. The advantage of Hall sensor-based commutation is that the control algorithm is simple and easy to understand. Hall sensor-based commutation can also be used to run the motor at very low speeds. The disadvantages are that its implementation requires both separate Hall sensors inside the motor housing and additional hardware for sensor interface.

• Sensorless commutation–In the sensorless commutation technique, the back-EMF induced in the idle phase is used to determine the moment of commutation. When the induced idle-phase back-EMF equals one-half of the DC bus voltage, commutation is complete. The advantage of sensorless commutation is that it makes the hardware design simpler. No sensors or associated interface circuitry are required. The disadvantages are that it requires a relatively complex control algorithm and, when the magnitude of induced back-EMF is low, it does not support low motor speeds. Furthermore, two voltage application techniques can be applied, based on the configuration of the supply-to-motor windings:
• Sinusoidal–Sinusoidal voltage is applied to the three-phase winding. Sinusoidal voltage provides a smooth motor rotation and fewer ripples.
• Trapezoidal–Here DC is applied to two phases at a time and the third phase is left idle. Trapezoidal voltage is simpler to implement and less complex.
 
When a BLDC motor application requires high torque when the motor is running at low speed, or when the motor is moving from a standstill, the Hall sensor commutation technique is an appropriate choice. A motor used in an electric bicycle application, for example, requires high initial torque and is a perfect application for Hall sensor commutation.

Regards,

Muzza.

[0037]

Thanks for the replies.  I understand how hall sensors work and such,
but I'm wondering specifically about this controller and if it acts as a
pedal-first controller if the hall sensors are not connected.

The GM website says it works with or without hall sensor signals, but
when there are no hall sensor signals, is it in the "get home mode" at
half speed or does it function like a pedal-first controller, where you
have to pedal to get the motor moving before you can give full
throttle?

How does this controller react to having no hall sensors connected?

[Noff]

I have this controller running without hall sensors since they have failed on my motor.
I notice no other difference than a need to pedal first from running with hall sensors, the speed wich is required for the controller to work is really low though (with my direct drive motor on 28" wheel) so I don't consider it big drawback.