User Manual

Table Of Contents

Brushless Motor Connections and Operation

126 Advanced Digital Motor Controller User Manual V2.0, July 8, 2019

Speed Measurement using the angle feedback Sensors

Information from Hall, SPI/SSI, sin/cos sensors, (and even Sensorless) is used by the con-

troller to compute the motor’s rotation speed.

When Hall sensors are used, speed is determined by measuring the time between Hall

sensor transitions. This measurement method is very accurate, but requires that the mo-

tor be well constructed and that the placement between sensors be accurate. On preci-

sion motors, this results in a stable speed being reported. On less elaborate motors, such

as low-cost hub motors, the reported speed may oscillate by a few percent.

Speed measurement is very precise with digital absolute sensors (SPI). Sin/Cos sensors

operating without noise also give a very precise value.

The motor’s number of poles must be entered as a controller parameter in order to pro-

duce an accurate RPM value. See discussion above. The speed information can then be

used as feedback in a closed loop system. Motor with a more precise Hall sensor posi-

tioning will work better in such a conﬁguration than less precise motors.

If the reported speed is negative when the slider is moved in the positive direction, you

can correct this by putting a negative number of poles in the motor conﬁguration. This will

be necessary in order to operate the motor in closed loop speed mode using hall sensor

speed capture.

Distance Measurement using Hall, SSI or other Sensors

When Hall sensors are used, the controller automatically detects the direction of rotation,

keeps track of the number of Hall sensor transition and updates a 32-bit up/down counter.

The number of counts per revolution is computed as follows:

Counts per Revolution = Number of Poles * 6

With Resolver or Sin/Cos sensors, the controller accumulates the sensor angle data to

recreate an accurate and high resolution 32-bit counter. For these sensors, the number of

counts per revolution is:

Counts per Revolution = Number of Sensor Poles * 512

With SSI sensor, the controller accumulates the SSI data difference to recreate an ac-

curate and high resolution 32-bit counter. For these sensors, the number of counts per

revolution is:

Counts per Revolution = Number of Sensor Poles * SSI Sensor CPR

The counter information can then be read via the Serial/USB port, CAN bus, or can be

used from a MicroBasic script. The counter can also be used to operate the brushless mo-

tor in a Closed Loop Position mode, within some limits