SoundTraxx DSD-150/DSX Owners Manual - Manual (Page 24)

24 Digital Sound Decoder Owner's Manual
calculate the value for CV 2, you can use the formula:
Desired Starting Voltage
CV 2 = 255 X ------------------------------------
Maximum Motor Voltage
If your DCC system supports Operations Mode Programming, an alternative method for setting Vstart is to turn your
throttle to the first speed step and then use the operations mode programming feature to increase the value in CV 2
until the locomotive just begins to move.
Set the Acceleration and Braking Rates
The DSD provides two CVs to simulate the momentum due to train weight. CV 3, Acceleration Rate, controls how
fast the locomotive responds to increases in throttle settings and CV 4, Braking Rate, controls how fast the locomo-
tive will respond to decreases in the throttle setting.
Both CVs can be programmed with any value between 0 and 255 (0xFF) with 255 corresponding to the slowest
acceleration or braking rate. Lower settings yield a more responsive locomotive which is useful for switching. When
both CVs are set to 0, the locomotive will respond nearly instantly to any throttle changes. A setting of 255, on the
other hand, will require
3.8 minutes for a locomotive to reach full speed from a standing stop!
The DSD’s Dynamic Digital Exhaust feature (see page 28) will be more dramatic with larger CV values and we
suggest setting CV 3 and CV 4 to a minimum value of 16 (0x10) or higher.
If you are using 14 or 28 Speed Step mode, setting CV 3 and CV 4 to any value greater than 0 will also improve the
DSD’s throttle response. While it is accelerating or braking, the DSD interpolates between speed steps so in effect,
your locomotive will respond as if it were being controlled with 128 speed steps. No more sudden lurching from one
speed step to another!
Select the Speed Table
The DSD provides 14 preset and one loadable speed tables which can be used for several purposes:
1. Matching the Auto Exhaust chuffing rate to locomotive speed.
2. Speed matching one locomotive to another.
3. Changing the feel of the throttle. For example, you could configure a switching locomotive so there are more
speed steps available at lower speeds for switching and fewer steps at high speeds where the locomotive is
seldom operated.
4. Compensating for an improperly designed driveline so the locomotive will operate within its prototypical speed
range.
CV 25, Speed Table Select, is used to select which speed curve will be used by the DSD. CV 25 may be programmed
with any value between 2 and 15 (0x02-0x0F) to select one of the preset speed curves shown in Table C, page 24.
The exact throttle response for each curve is shown graphically in the DSD Technical Reference under CV 25.
To select the user loadable speed table, set CV 25 to 16 (0x10).
In order for the speed table selection in CV 25 to take effect, CV 29 must also be programmed so the DSD knows to
use speed tables. Refer to the previous section "Configuring the Decoder" or the DSD Technical Reference to
determine the correct value for CV 29.