SoundTraxx LC Series Owners Manual - Manual (Page 20)

LC SERIES DIGITAL SOUND DECODER OWNER’S MANUAL 20
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.
Preset Speed Tables
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 to select one of the preset speed curves
shown in Table B. The exact throttle response for each curve is shown graphically below.
In order for the speed table selection in CV 25 to take effect, bit 4 of CV 29 must be set to 1.
Refer to the previous section “Configuring the Decoder” or the
LC Series Decoder Technical
Reference to determine the correct value for CV 29.
Set the User Loadable Speed Curve
The User Loadable Speed Table allows you to create virtually any throttle response curve you
can imagine. You will first need to design and program the Loadable Speed Table. The Load-
able Speed Table consists of 28 data points contained in CVs 67 through 94, each defining the
percentage of motor voltage applied at a give speed step. Each data point can contain a value of
0 to 255 corresponding to 0 to 100% of available motor voltage.
In 28 speed-step mode, each data point directly corresponds to a speed step. In 128 speed-step
mode, each data point corresponds to every four and a half speed steps. The motor voltage for
intermediate steps is interpolated by the DSD-LC to produce a smooth curve. In 14 speed-step
mode, alternate (odd numbered) data points correspond to speed steps 1-14. Important: all
28 data points must be programmed even for 14 speed-step mode or an unpredictable throttle
response may occur while accelerating or braking.
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
CV 25 Speed Curve Type
Straight LIne
Logarithmic Curve 1
Logarithmic Curve 2
Logarithmic Curve 3
Logarithmic Curve 4
Logarithmic Curve 5
Logarithmic Curve 6
Logarithmic Curve 7
Exponential Curve 1
Exponential Curve 2
Exponential Curve 3
Exponential Curve 4
Exponential Curve 5
Exponential Curve 6
User Loadable Speed Table
Table B. Speed Table Selection
100%
75%
50%
25%
0%
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
LOG
7
LOG
5
LOG
6
LOG
3
LOG
2
LOG
1
LOG
4
LINEAR
EXP
1
EXP
2
EXP
3
EXP
4
EXP
5
EXP
6
Speed Step
Motor Speed