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SKD224 replacement board

Assembly Manual

- Document version 0.1.6 –

© Copyright NMJ 2016

All rights reserved

SKD224 replacement board Assembly Manual

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Please read this manual carefully before carrying out the

installation!!! Although our products are very robust, incorrect

wiring may destroy the module!

During the operation of the device the specified technical parameters

shall always be met. At the installation the environment shall be fully

taken into consideration. The device must not be exposed to moisture

and direct sunshine.

A soldering tool may be necessary for the installation and/or

mounting of the devices, which requires special care.

During the installation it shall be ensured that the bottom of the

device should not contact with a conductive (e.g. metal) surface!


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Content

1. Important Information .............................................................. 4 2. Required tools .......................................................................... 4

3. Required materials ................................................................... 4 4. Operation principle .................................................................. 5

5. Board Connections ................................................................... 7

6. Disassembly of the SKD224 .................................................... 9 7. Installing the replacement board ............................................ 13

8. Replacement of the wheels .................................................... 18 9. Decoder settings ..................................................................... 25 10. Programming tips ................................................................... 26

11. Analog operation ................................................................... 28 12. Notes ...................................................................................... 28

13. CV Table ................................................................................ 29


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1. Important Information

The manual is a guide to assemble the SKD224 replacement

board and gives some decoder setting recommendations and

programming tips. The replacement board is a drop in replacement

for the original board situated inside the SKD locomotives chassis.

The replacement board contains a DCC decoder and a Smart

Power Supply (SPP) and is suitable for DCC operation. The

decoders have installed a dedicated firmware with factory default

parameter values optimized for the SKD224 locomotives. After a

decoder reset, all the decoder parameters are reverted to the factory

default values.

Reference documents: NA

2. Required tools

- tweezer

- screwdriver

- right plier

- cutter

- cutting plier

- soldering station

3. Required materials

- SKD224 replacement board kit containing the replacement axles

- soldering wire

Estimated assembly time: 30-45 minutes


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4. Operation principle

The SKD224 replacement board contains a smart power pack (SPP)

and is integrating a DCC decoder with BEMF PID motor control and

4 physical (function) outputs. The decoder controls the charging of

the on board 1 Farad capacitor, and ensures switching to the internal

power supply in case of track contact interruption. This guaranties a

trouble free running of the SKD224 even if the contact with the rails

is lost. The SPP is capable to power the locomotive up to 4 seconds

and can run it up to 30-50 centimeters without DCC power

(depending on the speed). This is especially useful for small 2 axle

locomotives like the SKD224, which has only a few current pickup

points, and suffer very often of DCC power interruption.

At start-up, the board will have a current consumption of 250-300

mA for up to 2 minutes, even if the locomotive is stationary. This is

normal, during this time the SPP is charging the internal capacitor.

In case of external power interruption, after the maximum allowed

timeout has been elapsed (this can be changed altering the specific

CV), the locomotive will stop. The operation can be resumed when

the locomotive is powered again over the rails.

Due to the operational principle, the SPP can be used only in DCC. If

the locomotive is used in DC, the SPP will be not activated.

The lights of the SKD224 are wired to the internal SPP circuit, so

even in the case of contact problems while running, during the

switching between external DCC power and internal SPP, the lights

are stable, and no annoying dimming is visible.

Connections for optional front/rear lights and electrical couplers are

available at both ends of the boards.


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The on board decoder is full of options: is featuring a SUSI

connector for optional sound module connection, contains Zero

Speed and ABC Braking, with penduling (push-pull operation), has

a RailCom transmitter, and is capable of driving different electrical

couplers. Future options can be also integrated with a firmware

upgrade.


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5. Board Connections

(the color coding is made according to NMRA standards, otherwise noted)

Motor Negative Terminal

Motor Positive Terminal

Coupler

Common

Coupler Output Coupler Output

Coupler

Common

Right Track Connection

Left Track Connection

Lights

Common

(See note 1)

Lights

Common

(See note 1)

Front

White

(See note 2)

Rear

White

(See note 2)

Front

Red

(See note 2)

Rear

Red

(See note 2)


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Note 1: The positive common terminal for the optional lights

(brown color in the illustration) is not the same as the coupler

positive common (blue in the illustration). It is forbidden to

connect them together.

The front/rear light outputs (white and yellow color) allows

direct connection of LEDs, so no current limiting resistors are

needed. The resistors are integrated to the boards. The Anode

of the LEDs must be connected to the Lights Common, while

the cathode to the front/rear outputs.


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6. Disassembly of the SKD224

Remove the housing from the chassis. Press in the same time on both

ends of the housing (1), and lift (pull) the housing in the upper

direction (2).

The housing has 4 plastic ears (3), which enters in the 4 recess of the

chassis (4). Using a sharp blade (cutter) can help in the extraction.

1 1

2

3 3

4 4


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Gently remove the housing, and place it on its side near the chassis.

Do not pull it too far, since the cabin lighting has a cable connection

to the chassis (2). The cabin itself also has 2 plastic pins (1), which

fits in the corresponding openings in the base plate located above the

chassis.

2

1


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Disconnect the cabin lighting by removing the connector from the

chassis printed circuit board.

Localize the track connections (1), motor connections under the

black adhesive tape (2) and the mounting screws (3) on the chassis of

the locomotive.

1

1

2

3

3


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First, unsolder the connection wires (4 in total).

Remove the 2 screws (1), and lift the printed circuit board. Please

note, that there are 2 mechanical centering pins (2) in the chassis,

which will guide the fit of the replacement board.

2

2

1

1


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7. Installing the replacement board

Lead the 4 connection wires thru the corresponding holes in the

replacement board, and fit the board to the chassis using the

mechanical centering pins. Screw the board to the chassis.

Solder the wires to the replacement board.


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All the wires must be pulled back, and arranged under the printed

circuit board. The motor connection wires must be arranged in such a

way to not touch the flywheel.

The track connection can be arranged on both sides of the chassis in

the available cutouts. If needed, a small drop of cyanoacrylate can be

used to fix the wires to the chassis.


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Half of the small adhesive tape from the original board can be used

to mask the side lighting of the LEDs of the central head lights.

Before reassembling the housing, removal of 2 small inside walls (1)

is necessary to assure the required space for the replacement board.

1


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This operation has to be performed using a cutter and a small plier.

The 2 interior walls must be cut with extreme care as close as

possible to the housing external wall without damaging it. After the

operation, clear the debris.

Insert the cabin light connector to the counterpart in the replacement

board.


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Insert the housing over the chassis, and press down until the plastic

ears fit the recesses of the chassis. The plastic ears of the cabin also

have to be fitted to the base plate.

After the housing is in its place, press the base plate in upper

direction while fitting the cabin plastic ears, till there is no distance

between the base plate and the housing.


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8. Replacement of the wheels

For the wheels/axles replacement, turn the locomotive upside down,

and place it on a stable surface to avoid falling on its side.

Pull the plastic ears on both sides of the base plate with a small

screwdriver to release it from the chassis (1). Lift the base plate in

upper direction (2).

1 1

2


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Remove the 2 original axles with the plastic toothed wheels from the

chassis. The axle’s assembly keeps the current pickups pressed to the

wheels, while removing them the current pickups will depart from

the chassis.

At this point since there is access to the gearbox, it could be a good

idea to apply some grease over the wheels if needed. However, this

can be done at a later time too. You can use Roco type grease part

number 10905.


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In the illustration an exaggerated quantity of grease is applied for

exemplification. Use the grease in a moderate quantity.

Apply it also on the intermediary toothed wheels too.

Insert the replacement axles with the brass toothed wheels. They

must be inserted starting from the inner side of the chassis (1),

moved to the correct position (2) while pressing the elastic current

pickups to touch the wheels from their inner side (3).

2

1

3


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Press the axles in down direction when they are in the correct

position.

Continue with the insertion of the second axle (1) and move it to the

correct position (2).

1

2


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Press it down, to fit perfectly in the recess. Please take extreme care

about the correct positioning of the axles/wheels, since they have a

major influence over the running performance of the locomotive.

The grease can be applied also at this stage. As it is mentioned, use a

moderate quantity.


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Drop a small quantity of fine mechanical oil at each axle/chassis

contact surface. Please use good quality oil, as the Roco 10906.

Place the base plate over the gearbox/chassis, and press it in down

direction at both sides to close it completely.


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After the wheels/axles replacement, we recommend to drive the

locomotive in both forward and reverse direction for about 20-30

minutes.

A Roller Tester device can be used for this operation.


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9. Decoder settings

The factory default setting maps the F0 function direction dependent

to the front and rear lights (FL and RL), and the F1 function to the

cabin light (AUX1/Out3).

FL front side high beam reflector (Out1)

RL rear side high beam reflector (Out2)

AUX1 cabin interior light (Out3)

AUX2 Not Used by default, connected

to the optional electrical coupler

outputs at both ends of the board (Out4)

The light intensity of the front/rear side high beam reflector and the

cabin light can be changed in CV48-49-50. In the factory settings,

these are configured for maximum intensity.

The decoder is preset for 28/128 speed step operation, no dc mode.

To take the full advantage of the BEMF motor control, we

recommend driving your locomotive with 128 speed steps. The

RailCom transmitter is sending the locomotive address in broadcast

mode. By default, the following function mappings are valid:

F3 shunting speed

F4 acceleration / deceleration OFF

F5 constant braking distance OFF

These mappings can be changed by altering the CVs 33-47. The

stopping configuration (CV27) by default has active only the Zero

Speed Brake option. Electrical coupler, ABC braking and penduling /

push-pull operation is disabled.


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10. Programming tips

The SPP timeout is set by default to its maximum value 255, which

results in a ~ 4 second autonomy of the decoder in case of a DCC

power failure. This is useful, but has it’s withdraw: the locomotive

will be uncontrollable till this time expires. To avoid this, the SPP

timeout settled in CV123 can be decreased till a convenient value.

The Output4 (AUX2) of the decoder can be used for switching an

optional electrical coupler. First of all, we have to map a function to

this output (CVs 33-to 47). For example mapping F6 for the

electrical coupler will be made by changing the CV41 from the

default 0 value to 8.

Then we have to activate the coupler effect on the Output4 (AUX2).

This will be done by specifying in CV118 the Output4. Write in

CV118 the value 4.

The electrical coupler effect can be configured for only pwm action

(CV124=0, default value), or for some specific couplers which need

a full powered drive signal for a certain amount of time, and pwm

after the coupler is activated (CV124=1).

During the coupler operation the locomotive can be configure for the

typical “waltzer” (back, kick, and forward) movement. The back

movement and kick time is specified in CV119, while the forward

moving time and speed in CV120 and CV121. The settings of these

CVs can be done in several iterations by trial. During this coupling

operation the directional headlights of the locomotive will be not

switched. This “waltzer” movement is valid only if one of the 4

outputs is configured for coupler effect.

The Constant Braking Distance (CBD) is active by default (CV27

bit7 = 1). This will be taken inconsideration if the Zero Speed Brake

(active by default) or ABC braking (inactive by default) is requested.


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The stopping distance should be determined at maximum speed step.

This can be done by altering the default 3 value of CV137 to 1,

which means the shortest possible stop distance (this distance

depends on the locomotive mechanical construction and gear box

configuration). This can be increased using a higher value for

CV137, and/or applying a braking delay in CV138. CV138=0 means

no braking delay applied over the stopping distance. These setting

must be done in several iteration by trial and error. In braking

condition, the locomotive will decelerate according to the constant

braking distance, and not base on CV4 (deceleration rate). However,

changing the speed of the locomotive (not to zero speed) will use the

deceleration rate settled in CV4. The constant braking distance can

be switched off with the F5 function (default configuration). The

function mapping can be changed altering CV116.

The stopping condition of the locomotive can be requested with the

help of ABC braking modules. The activation of this option is made

in CV27, bit0 (on right rail) and bit1 (on left rail). Either one or both

of these options can be used. If there is an uncertain situation while

detecting the ABC sections, the sensitivity of the ABC braking sector

detector can be increased by higher value than the default 15 in

CV134. Combining the ABC braking with the constant braking

distance will stop your locomotive in an exact position.

The locomotive can perform a so called penduling / push-pull

operation. For doing this, two braking sector must be present at both

ends of a straight track. The ABC braking must be configured in

CV27 for both directions (right and left rail too). The locomotive will

run from end A to end B of the track, where it will detects the

braking condition, will stop, and will wait till the waiting time

specified in CV133 will elapse. Then it will start to run in reverse

direction till it reaches end A, where it will stop again, wait, and so

on. If during this operation a new speed step command is sent to the

decoder from the central station, it will override the penduling


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operation, and the locomotive can be controlled manually. If the

constant braking distance is active during the penduling operation,

the stopping of the locomotive at A/B ends will be done according to

the specified braking distance.

11. Analog operation

The analog operation of the SKD224 replacement board is not

activated by default to allow the operation of the SPP circuit.

However, the activation of the DC operation can be made by altering

the default CV29 value. Changing CV29 from the default value of 10

to 14 will activate the DC operation, but in the same time it will

deactivate the SPP.

12. Notes


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13. CV Table

In the table below you will find the complete list of configuration variables (CVs) of the DCC decoder

built in the SKD224 replacememt board. We recommend to change the default values only if you know their

function. Wrong settings can have negative effect ower the performance of the locomotive, or can cause non-

expected actions to the DCC commands sent by the command station. The CV No. column contains the

number of the configuration variables, while the Value Range contains the valid range of values for each of

the CVs. The Default Value column contains the factory default values for each CV optimised for the

SKD224 (after performing a decoder reset each CV will contain this value). The Description column will

give you a brief description of each of the CVs. To perform a decoder reset (in case of wrong CV settings)

please write any numerical value to CV8.

CV Default

Value

Value

Range Description

1 3 0-127 Decoder Adresse Short, 7 bits

2 4 1-127 Vstart

3 7 0-63 Acceleration Rate 0=Fastest acceleration

4 5 0-63 Deceleration Rate 0=Fastest deceleration

5 60 1-127 Vhigh

6 30 0-127 Vmid, recommended value = [25%-75%] Vhigh


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7 1 - Software Version (only readable)

8 78 - Manufactured ID/RESET (readable 78 = train-O-matic, any written value

will reset the decoder to the factory default values

9 3 0-9 Motor Control Algorithm, 0-8

User defined = 9 (see CV 60)

13 0 0-255 Analog Mode, Alternate Mode Function Status F1-F8

Bit 0 = 0(0): F1 not active in Analog mode

= 1(1): F1 active in Analog mode












= 1(64) F7 active in Analog mode




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14 3=

1+

2

0-255 Analog Mode, Alternate Mode Function. Status F0f,F0r, F9-F14,

Bit 0 = 0(0): F0f not active in Analog mode

= 1(1): F0f active in Analog mode

Bit 1 = 0(0): F0r not active in Analog mode

= 1(2): F0r active in Analog mode










= 1(64) F13 active in Analog mode



15 0 0-7 LockValue: Enter the value to match Lock ID in CV16 to unlock CV

programming. No action and ACK will be performed by the decoder when

LockValue is different from LockID. In this situation only CV15 write is

allowed.


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16 0 0-7 LockID: To prevent accidental programming use unique ID number for

decoders with same address (0..7) For example: 1-loco decoder, 2-sound

decoder, 3-function decoder, …

17 192 192-255 Extended Address, Address High

18 3 0-255 Extended Address, Address Low

19 0 0-127 Consist Address

If CV #19 > 0: Speed and direction is governed by this

consist address (not the individual address in CV #1 or

#17+18); functions are controlled by either the consist

address or individual address, see CV’s #21 + 22.

21 0 0-255 Functions defined here will be controlled by the consist address.

Bit 0 = 0(0): F1 controlled by individual address

= 1(1): …. by consist address











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22 0 0-63 Functions defined here will be controlled by the consist address.

Bit 0 = 0(0): F0 (fwd.) controlled by individual address


Bit 1 = 0 (0): F0 (rev.) controlled by individual address










27 128=

0-7 Decoder Automatic Stopping Configuration

Bit 0 = 0(0): Constant Braking Distance on right rail disabled

= 1(1): Constant Braking Distance on right rail enabled


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128

Bit 1 = 0 (0): Constant Braking Distance on left rail disabled

= 1(2): Constant Braking Distance on left rail enabled

Bit 3 = 0(0): DC Braking disabled

= 1(8): DC Braking enabled

Bit 7 = 0(0): STOP/Zero Speed Braking disabled

= 1(128):STOP/Zero Speed Braking enabled

28 1 1-3 RailCom Configuration

Bit 0 = 0(0): Address broadcast on Channel 1 disabled

= 1(1): Address broadcast on Channel 1 enabled

Bit 1 = 0(0): Data transmission on Channel 2 disabled

= 1(2): Data transmission on Channel 2 enabled

29 10=

2+

8

0-63 Configuration Data

Bit 0 = 0(0): Locomotive Direction normal

= 1(1): Locomotive Direction reversed

Bit 1 = 0(0): 14 speed steps

= 1(2): 28 /128 speed steps

Bit 2 = 0(0): Power Source Conversion NMRA Digital Only (only DCC)

= 1(4): Power Source Conversion Enabled (DC + DCC)

Bit 3 = 0(0): RailCom disabled

= 1(8): Railcom enabled

Bit 4 = 0(0): speed table set by configuration variables #2,#5, and #6

= 1(32): Speed Table set by configuration variables #66-#95


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Bit 5 = 0(0): one byte addressing (short addressing)

= 1(64): two byte addressing (extended/long addressing)

Bit 6 -Not Used

Bit 7 -Not Used

30 0 0-7 Error CV. If the read out value is “1”, an overcurrent event occurred since

the last reset. The value can be cleared with programming “0” to CV30

Error Information (combination of each values are possible):

0-No error

1-Motor Short Protection

2-Aux Output Short Protection

4-Overtemperature

33 1=

1

0-15 F0, Forward move mapping

Bit 0 = 0(0): Out1 not active on F0 forward

= 1(1): Out1 active on F0 forward







34 2=

0-15 F0, Backward move mapping

Bit 0 = 0(0): Out1 not active on F0 backward


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2

= 1(1): Out1 active on F0 backward







35 4=

4

0-15 F1, Forward move mapping









36 4=

0-255 F1, Backward move mapping







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4 = 1(4): Out3 active on F1 backward



37 0=

0-255 F2 mapping

Bit 0 = 0(0): Out1 not active on F2

= 1(1): Out1 active on F2







38 0 0-255 F3 mapping









39 0 0-255 F4 mapping


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40 0 0-255 F5 mapping









41 0 0-255 F6 mapping






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42 0 0-255 F7 mapping









43 0 0-255 F8 mapping










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44 0 0-255 F9 mapping









45 0 0-255 F10 mapping









46 0 0-255 F11 mapping





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47 0 0-255 F12 mapping









48 255 0-255 Out 1 Light intensity, [1-255]




56 0 0-1 Save last Function state if CV value = 1

60 3 0-7 and

128-135

Motor, Back EMF measurement Delay

value of 0 or 128 swithes BackEMF Off, value>0 or > 128 changes the


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BEMF measurement Delay. Delay(ms)=0.75+CV Value*0.25

Bit7=0 uses 32kHz PWM (CV range 0-7)

Bit7=1 uses 16kHz PWM ( CV range 128-135)

61 80 0-255 PID P constant

62 120 0-255 PID I constant

63 40 0-255 PID D constant

67 2 1-127 Speed Table 1-28 ST[1] 1 position speed value

….. Throttle position speed mapping values, ex. 1 position=2 speed, 28

position=120 speed

94 120 1-127 ST[28], 28 position speed value

105 0 0-255 USER data, freely configurable. It is not cleared after a decoder reset

106 0 0-255 USER data, freely configurable. It is not cleared after a decoder reset

112 15 1-127 Fade ON effect on outputs, ex.:1=8ms, 15=120ms 125=1000ms

113 3 1-127 Fade OFF effect on outputs, ex.:1=8ms, 15=120ms 125=1000ms

114 4 0-255 Shunting speed, Function mapping F1-F8, F3 default (bit 0 is mapping F1,

bit 7 is mapping F8). Mapping is possible only for F1-F8

115 8 0-255 Switch Off Acceleration Deceleration, Function mapping, F4 default (bit 0

is mapping F1, bit 7 is mapping F8). Mapping is possible only for F1-F8

116 16 0-255 Disable Constant Braking Distance, Function mapping, F5 default (bit 0 is

mapping F1, bit 7 is mapping F8). Mapping is possible only for F1-F8

117 0 0-15 Bit 0 = 0(0): Out1 could be dimmed and faded


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= 1(1): continues signal with no fading on Out1

Bit 1 = 0(0): Out2 could be dimmed and faded






118 0 0-4 Electrical Coupler Output mapping for the 1-4 outputs. Only one of the

outputs can be configured as ECoupler Output

CV118 = 0, None of the AUX selected for ECoupler operation

CV118 = 1, Out1 selected for ECoupler operation




119 50 0-255 Electrical Coupler, Kick_time = Val*8ms, ex: 400ms=50*8ms

120 50 0-255 Decoupling, Locomotive move Time=Val*8ms, ex: 400ms=50*8ms

121 50 0-255 Decoupling, Locomotive moving speed

122 1 0-1 Second Configuration,

Bit 0 = 0(0): SUSI interface disabled

= 1(1): SUSI Interface enabled

Bit 1 = 0(0): Push Pull Operation disabled

= 1(2): Push Pull Operation enabled


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123 255 0-255 SPP (Smart Power Pack) Timeout=16ms*Value Ex: =16ms*255=~4s

124 0 0-1 ECoupler Mode

CV124 = 0, PWM Output

CV124 = 1, Full Output startup + PWM Output for sustaining the coupler

on selected A in CV118

126 102 0-255 SUSI CV transport, SUSI CV=800+Value

127 0 0-255 SUSI DATA transport, Data write to CV=800+cv126

131 Chip temperature read out (the value is expressed in degrees Celsius. The

precision of the readout is +/- 2 degrees). Prior to the readout the F5

function must be switched On and Off

132 100 60-120 Temperature Limit for the temperature protection (value in degrees

Celsius)

133 10 0-255 Penduling / Push-Pull Wait Time

134 15 0-31 ABC Breaking Sensitivity

137 3 0-15 Brake Distance configuration

0-No brake

1-15 Braking rate, the CV value influences the Constant Braking Distance,

CV137=1 means the Shortest Braking Distance from maximum Speed to

STOP. Increase the CV value to increase the braking distance.

Distance=Value * Shortest Breaking Distance


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138 25 0-255 Brake Delay Configuration

CV138= 0 means no Brake Delay. To increase breaking distance above the

value configured in CV138, increase in small amounts the value of CV65,

which will delay the start of the braking, resulting in a longer braking path.

Brake Delay = CV138 Value * 8ms (ms)

Extra Distance = MaxSpeed * BrakeDelay

Ex: 200ms(delay)=8(ms)*25(CV value)


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NMJ - Norsk Modelljernbane AS

Copyright © 2016 NMJ

All rights reserved

The information in this document is subject to change without

notice

Ensjøveien 7,

0655 Oslo

Tel: (+47) 64 84 57 30

Fax: (+47) 64 84 57 39

www.nmj.no [email protected]

http://www.nmj.no/

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