SoundTraxx LC Series Owners Manual - Manual (Page 19)

LC SERIES DIGITAL SOUND DECODER OWNER’S MANUAL 19
Step 3: Configuring the Throttle
There are eight CVs that characterize the DSD-LC’s throttle response and 28 more used to
create a custom speed table:
CV 2, VStart
CV 3, Acceleration Rate
CV 4, Braking Rate
CV 9, Motor PWM period
CV 25, Speed Table Select
CV 29, Configuration Data
CV 66, Forward Trim
CV 95, Reverse Trim
CV 67-94, Loadable Speed Table
This may sound like a lot of CVs but don’t worry; it’s not necessary to change all of them if you
don’t want to. We’ve already talked about speed step selection in CV 29 (Step 2).
Set the Start Voltage
The DSD-LC provides CV 2, Vstart, to set the starting voltage that is applied to the motor
at Speed Step 1 and is used to compensate for inefficiencies in the locomotive’s motor and
driveline. CV 2 may be programmed with any value between 0 and 255 with each step in value
being about 0.5% of the maximum available motor voltage. To calculate the value of 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-LC 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 locomotive will respond to decreases in the throttle
setting.
Both CVs can be programmed with any value between 0 and 255 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 several minutes for a
locomotive to reach full speed from a standing stop!
The DSD-LC’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 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-LC’s throttle response. While it is accelerating or braking, the DSD-LC
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-LC provides 14 preset and one loadable speed table that can be used for several
purposes: