Page 20 Non-Sound Decoder MX618 - MX638 and Sound Decoder MX640 - MX659
CV
Denomination
Range
Default Description
#58
BEMF intensity
0 - 255
255
Intensity of back-EMF control at the lowest speed step.
If required, an “intensity curve” can be achieved using
CV #10, 58 and 113 to reduce load regulation at higher
speeds.
Example:
# 58 = 0: no back-EMF
# 58 = 150: medium compensation,
# 58 = 255: maximum compensation.
#10
Compensation cut-off
This CV is seldom required
0 - 252
0
Assigns an internal speed step where back EMF inten-
sity is reduced to the level defined in CV #113. CV #10,
#58 and #113 together define a back-EMF curve.
= 0: default curve is valid (as in CV #58).
#113
Compensation cut-off
This CV is seldom required
0 - 255
0
The BEMF intensity is reduced to this value at the
speed step defined in CV #10.
CV #113
together with CV’s #58 and #10 form a 3-point
BEMF curve.
= 0: actual cutoff at speed step in CV #10. Usually
CV #10 is also set to 0.
#145
#147
#148
#149
#150
Exper
imental CV’s for
test purposes,
to find out whether
certain automatic
settings have a negative
effect on motor
regulation.
Using these
experimental CV’s will
deactivate the automatic
settings.
CV’s #147 – 149 will
likely be removed again
from the decoder SW at
some time.
CV #145 = 10,11,12,13
for C-Sinus motors
See chapter 6 (Installa-
tion)
0
0
0
0
0
--- CV #145 = 1: Special setting for Fleischmann round
motor.
--- CV #147 Sampling time ---
Useful initial value: 20;
Too small a value leads to jerky behavior.
Too large a value leads to poor low speed control.
0=
automatic control (CV #147 has no effect)
--- CV #148 D-Value ---
Useful initial value: 20;
Too small a value leads to poor regulation (regulates
too little, too slow, engine judders (rather slowly).
Too large a value leads to over compensation, the en-
gine runs rough/vibrates.
0 = automatic control (CV #148 has no effect)
--- CV #149 P-Value ---
0 = automatic control (CV #149 has no effect)
1 = P-Value is fixed as per CV #56 (tens digit)
--- CV #150 Load compensation at top speed ---
Load compensation at top speed is normally always 0.
This can be changed with CV #150.
Example: CV #58 = 200, CV #10 = 100, CV #113 = 80
und CV #150 = 40 --> Result: Regulation at speed
step 1 is 200 (of 255, almost 100%), at speed step 100
it is 80 (@1/3
rd
of 255), at speed step 252 (full speed) it
is 200 (of 255, almost fully regulated).
We kindly ask for your cooperation. Please send us
your test results!
The Motor Brake
This brake is useful for vehicles without worm gears to prevent them from rolling away on inclines, picking up speed
on declines as well as to prevent a heavy train from pushing a standing engine downhill.
CV
Denomination
Range
Default
Description
#151
Motor brake
0 - 99
0
= 0: brake not active
Ones digit: 1 - 9: The motor brake is gradually actuat-
ed (over a period of
1, 2 … 8 seconds, up to full brak-
ing power by shorting both motor power amplifier) if
target speed is not reached (not slowing down) after
cutting power to the motor (Zero PWM to the motor).
The higher the value, the faster and harder the brake
is being applied.
Tens digit: 1-9: Reduction of the motor regulation if
consist-key is active. The values 1-9 reduce the con-
trol to 10%-90% of the value set in CV #58.
3.7 Acceleration and Deceleration:
The basic acceleration and deceleration times (momentum) are set with
CV’s #3 and #4
according to the relevant NMRA standard, which demands a linear progression (the time between
speed step changes remains constant over the whole speed range). For simple smooth drivability use
values 3 or higher but for really slow starts and stops start with a value of 5. Values over 30 are usual-
ly impractical!
Acceleration and deceleration behavior, especially starting and stopping, can be further improved by
the “exponential” and “adaptive” acceleration/deceleration features (CV’s #121, 122 and 123).
The sound project in sound decoders always comes with different values in C
V’s #3 and #4 (as well as
many other CV’s) than what is listed in the CV charts. Often the sound can only be played back correct-
ly in conjunction with the acceleration times provided by the sound project (or certain minimum values),
so
the sound project’s default values should therefore not be changed too much.
To eliminate a start-up jolt after changing the direction, caused by gear backlash in gearboxes, use
CV #146: Some free play between gears of a drivetrain is essential to prevent them from binding. This
creates backlash and may be more severe on some engines than on others, especially when fitted
with a worm gear or an excessively worn gearbox.
CV
Denomination
Range
Default Description
#3
Acceleration rate
0 - 255
(2)
The value multi
plied by 0.9 equals’ acceleration time in
seconds from stop to full speed.
The effective default value for sound decoders is usual-
ly not the value given here, but is determined by the
loaded sound project.
