Asymmetrical Dcc-Signal" Stops (Lenz Abc) - ZIMO MX638 Series Instruction Manual

Non-Sound Decoder MX600 - MX638 and Sound Decoder MX640 - MX659
The deceleration (often CV #52 for "U" limit) and brake (CV #4 and #50) characteristics should be set so that
all locos come to a complete stop within about 2/3 of the stop section, which in HO is typically about 15 to 20
cm before the end of a stop section. Setting the loco up to stop precisely within the last centimeter of a stop
section is not recommended.
CV Denomination Range Default Description
Signal controlled
#49 (HLU, ABC) 0 - 255
acceleration
Signal controlled
#50 (HLU, ABC) 0 - 255
deceleration
Signal controlled
(HLU) speed limits
#51
#51
0 - 255
#52 for "U" (Ultra low)
-
#53
#55
#54 for "L" (Low speed)
110 (L)
#55
180
Signal controlled
#59 (HLU, ABC) 0 - 255
delay
Entered value multiplied by .4 equals acceleration time
in seconds from stop to full speed when:
"ZIMO signal controlled speed influence" with ZIMO
0
MX9 track section module and successors
or
"asymmetrical DCC signal" method (Lenz ABC) is em-
ployed
Entered value multiplied by .4 equals deceleration time
in seconds from full speed to complete stop when:
"ZIMO signal controlled speed influence" with
0
ZIMO MX9 track section module and successors
or
"asymmetrical DCC signal" method (Lenz ABC) is em-
ployed.
ZIMO "signal controlled speed influence" method (HLU)
20 using MX9 or successor:
40 (U)
Defines the internal speed steps for each of the 5
70
speed limits generated via HLU.
ZIMO signal controlled speed influence (HLU) with
ZIMO MX9 track section module or future module
or
when using the "asymmetrical DCC signal" stopping
5
method (Lenz ABC):
Time in tenth of a second until the locomotive starts to
accelerate after receiving a higher signal controlled
speed limit command.

3.10 "Asymmetrical DCC-Signal" stops (Lenz ABC)

SW-Version 36.1 and higher: also working with ABC (for example: Lenz-module BM2)
The "asymmetrical DCC signal" is an alternative method for stopping trains at a "red" signal. A simple
circuit made up of 4 or 5 commercially available diodes is all that is required.
Track power from
command station
Note:3 diodes in series is
Switch to
the minimum required to
cancel stop stop ZIMO decoders. 4 or
when signal more diodes are sometimes
turns "green"
needed for other decoder
brands. Because the diodes
cause an undesired voltage
Silicium diodes,
drop, use the minimum
i.e. 1N5400x
number of diodes possible.
(3 A - Types)
red
Stop section Main track
"Gold" decoder from Lenz.
The asymmetrical threshold (0.4V by default) can be modified with CV #134 if necessary (i.e. if the
DCC signal of a given command station is already offset to begin with). At the time of this writing, the
"asymmetrical DCC signal" has not been standardized and many DCC systems pay no attention to
this feature.
Note: the ABC slow speed supported by Lenz decoders (i.e. by the Lenz module BM2) is supported
by ZIMO decoders from SW-version 36.1.
CV Denomination Range
Direction
dependent stops
with asymmetrical DCC
#27 0, 1, 2, 3
signal
(Lenz "ABC" method)
#49, Acceleration-,
0 - 255
#50 deceleration time
#53 ABC slow speed 0 - 255
Page 23
3 to 5 silicon diodes in series and one
Schottky diode in parallel in the op-
posite direction is the usual arrange-
ment. The different voltage drops
across the diodes results in an asym-
metry of about 1 to 2V. The direction in
which the diodes are mounted deter-
mines the polarity of the asymmetry
and with it the driving direction a signal
stop is initiated.
Travel direction
The asymmetrical DCC signal stop
mode needs to be activated in the de-
coder with CV #27. Normally Bit 0 is
set, that is CV #27 = 1, which results in
the same directional control as the
Default Description
Bit 0 = 1: Stops are initiated if the voltage in the right
rail is higher than the left rail (in direction of
travel). This setting, CV #27 = 1, is the com-
mon application for this feature (provided the
decoder is wired to the rail correctly).
Bit 1 = 1: Stops are initiated if the voltage in the left rail
is higher than the right rail (in direction of
0
travel).
Stopping is directional if only one of the two bits is set
(not both). Traveling in the opposite direction will have
no effect. Use the other bit in case the train stops in the
wrong direction!
Bit 0 and Bit 1 = 1 (CV #27 = 3): Stops in both
directions, regardless of rail polarity.
See chapter HLU.
0
70 Internal speed steps for the ABC slow speed