Diesel Version 5:3 Point Speed Curves Feature
In most applications of acceleration and deceleration the rate at which a locomotive increases its speed forms a curve where the early speed steps do not increase the speed as rapidly as later speed steps. Whereas User Loadable Speed Tables have 28 individual speed steps to adjust and allows for speed plateaus, dips, and non-continuous speed curves, for most applications a simple Speed Curve will be more than adequate to create the prototypical movement of most locomotives. To this end Speed Curves employs 3 CV’s, each defining the rate of speed of a given range of speed steps. Using the Start Volts, Mid Volts, and Top Volts the speed steps from 1-128 are divided into three equal sections. Adjusting the values in the corresponding CV’s shifts the standard speed curve up or down (within the specific range) thereby creating an entirely new rate of speed from each speed step to the next. CV 2 CV 6 CV 5 3 Point Speed Curves Usage and Adjustment:To enable 3 Point Speed Curves simply program values into CV 2 (Start Volts), CV 6 (Mid Volts), and CV 5 (Top Volts). The Speed Curve is defined in CV’s 2, 6 and 5 with each CV corresponding to approximately 1/3 of the speed range. Values may range from 1-255 and every value of18 (approximately) added to one of the Speed Curve CV’s adds about 1 volt to the motor speed at the CV being adjusted. NOTE:3 Point Speed Curves do not allow for parabolic speed curves.That is to say each consecutive CV must have a value higher than, or equal to, the CV before it.
| Base Functionality | |
|---|---|
| Range of Values | 0-255 |
| Default Value | 0 |
NMRA CV 2 - Vstart (Start Volts)
CV 2 Adds an offset voltage to the motor so that the locomotive starts moving at a faster speed. This is useful for speed matching or for locomotives without BEMF. this setting is also useful for inefficient electric motors which have require a higher voltage to overcome "stall current." Some motors may lurch or repeatedly stop and start if the start volts are too low. Increasing the start volts can improve performance by increasing the low-end power.
From the NMRA standard:
Vstart is used to define the voltage drive level used as the start voltage on the motor. The voltage drive levels shall correspond linearly to the voltage applied to the motor at speed step one, as a fraction of available rectified supply voltage. When the voltage drive level is equal to zero, there shall be zero voltage applied to the motor. When it is at maximum (255), the full available rectified voltage shall be applied.
| VHigh | |
|---|---|
| Range of Values | 0-255 |
| Default Value | 0 |
NMRA CV 5 - Vhigh (Top Volts)
Vhigh is used to specify the motor voltage level at maximum speed. This value is a fraction of available voltage. When the contents of CV#5 equal 255 the full available voltage will be applied. Values of 0 or 1 indicate that Vhigh is not used in the calculation of the speed table. VHigh require no other CV programming to be activated.
| Vmid | |
|---|---|
| Range of Values | 0-255 |
| Default Value | 0 |
NMRA CV 6 - Vmid (Mid Volts)
Vmid specifies the voltage drive level at the middle speed step. Vmid is used to generate a performance curve in the decoder that translate speed step values into motor voltage drive levels and is specified as a fraction of available rectified supply voltage. Values of 00000000 or 00000001 shall indicate that Vmid is not used in the calculation of the speed table.
CV6 is used in conjunction with CV2 and CV5 as part of the 3 Point Speed Curves feature
