CV 179

CV 179

BEMF Sensitivity B Range of Values 5-255 Accepted Values 5-255 Default Value Varies

NMRA CV 179 - BEMF Sensitivity B

CV 179 can be used to configure how quickly the BEMF algorithm will react to changes Below the "Critical Speed Step" (CV 181).

Geek Speak: At speeds where the coefficient of static friction isn't readily overcome, the decoder must make BEMF adjustments more often to account for the motor response time being faster. Once static friction is overcome, the motor output must be cut back more quickly to keep the motor from overshooting.

The speed/RPM at which this transition occurs will vary based on the type of motor, gear ratio, etc. Usually this speed step is 7 (of 128) or below. This CV is used to set a speed step at which the behaviour of the BEMF changes. Through the use of This CV, as well as CV 178, you can set up two different levels of "responsiveness" for the BEMF algorithm. This feature is most useful with 3-pole and "coreless" motors which tend to have dramatically different BEMF swings depending on the RPM. A lower delay time is better for "stiffer" motors and motors with a fast response time like coreless motors.

!!!WARNING!!! This CV should not be modified unless you are trying to correct a significant issue with slow speed motor control. We do not suggest modifying this CV unless absolutely necessary.

This "responsiveness" refers to the motor control itself, not necessarily the sound functions such as chuff intensity or prime mover RPM. Refer to our section on Prototype Throttle Mode for guidance on BEMF calibration for sound function.

NOTE: This CV was introduced at different times in different decoders. This CV will not do anything if programmed with a value on a decoder which does not support the feature.

Only current-generation decoders (V4.5 Diesel, V4.6 Steam, V90+ Mobile) support this CV and featureset.

Related:

• CV 177 - Motor Power Stroke
• CV 178 - BEMF Speed A
• CV 181 - Critical Speed Step
• CV 182