Suggested Settings

The Tradeoffs

In a brushed dc motor the position of the commutator, the armature windings and the magnets are set in the correct position mechanically.

But in a brushless system at initial start the eCom has to go through a procedure to discover the position of the rotor.

To avoid excessive current while this initial alignment and rotation is carried out pulse width modulation (PWM) is in action to control the power applied to the motor.

We set duty_min and duty_max to 100% and instruct the firmware to turn off PWM entirely once the initial alignment and rotation is complete and PWM is no longer present.

The motors we are using have a very low inductance, meaning that when PWM is applied the current is not a nice smooth waveform and it has high current peaks which can cause the hand-controller, the eCom and the motor to run hotter than with a smooth waveform.

To reduce the current peaks it is beneficial to have a higher freq_max, but this might cause some losses that are affected by frequency to increase. More info. about tuning.

Recommended Settings

Parameter	Default Value	Comment
revdir	0	change this if motor runs backwards, so you do not have to re-solder the motor wires.
timing	16	a higher value might result in more speed, but at the expense of brakes. Higher advance might be needed to sync Kv motors >10,000Kv, but the default value works well for a wide variety of motors.
duty_min	100	setting it to 100% gives you a fast start. This duty cycle is applied at analog_min.
duty_max	100	set it to 100%, but if for any reason you do not want the car to have its highest top speed this can be reduced, but duty_min should be the same or less.
freq_min	48	use the highest value of 48kHz. Remora will use this frequency for PWM during its startup procedure. We set this to the highest value assuming current peaks are very high and to aid starting the motor. Note: There may be some interaction with duty_spup.
freq_max	96	use the highest value of 96kHz. Remora will use this frequency for PWM during its startup procedure and once running if duty_max is less than 100%. We set this to the max assuming current peaks are high.
duty_spup	20	higher values give a higher duty cycle percentage during initial alignment and rotation until the first synchronised revolution, but it may result in excessive current. Just be careful if you increase this.
duty_ramp	100	Set this to the maximum.
duty_rate	25	rate of increase of PWM during the initial alignment and rotation from a standing start. 25 is 40mSec (10÷25). Should the motor stutter, try decreasing this value, i.e. a longer time, but not too low, or else the car will be very sluggish off the line.
duty_drag	0	best to turn this off. Drag brakes come into effect below the ANALOG_MIN - if this is set at or below the eCom energization voltage (1.2V starting, 1.16V decreasing) it has no effect. This sets the duty cycle percentage.
analog_min	0	it's most beneficial to set this to 0.
analog_max	1440	the voltage at which duty_max takes effect. Probably meaningless if duty_max and duty_min is 100. It's usually set to 8VDC which is probably lower than any track voltage even for some club nights when we run the track at 10VDC (1801×8 = 1440). Make sure it's higher than analog_min.

Footnotes

1: For the technically mined - the 180 value is a fixed ratio of the resistances in the BEMF voltage divider circuit on the board.