e00a062.pdf

GENERAL INTEREST

Märklin Digital Model

Final part: software, construction and operation

From an idea by J. Schröder

Figure 3. Screenshot of the Windows program written for the train control system.

The Software

In addition to this circuit, a PC is necessary

onto which the requisite Windows program

needs to be installed. Continuing in the spirit

of simplicity, manual controls are not pro-

vided. The system requirements have been

kept to a minimum. Practically any PC should

be capable of performing the task.

This applies also to the minimum

required version of Windows. The

time-honoured Windows 3.1x meets

the needs admirably. In addition,

provision has been made to make

keyboard operation possible. Experi-

ence shows that, once familiar with

the keystrokes, this method of oper-

ation is extraordinarily convenient

and fast.

After starting the software, a

screen will appear as depicted in

Figure 3 . For language purists, there

Elektor Electronics

10/2000

Train Control (2)

GENERAL INTEREST

is the built in facility to customise

the labels of the buttons to your

heart’s content.

At the top are the (fixed) loco

address configurations: first the

Märklin loco address, below that, the

Delta loco address of the four applic-

able controls.

The slider (can also be operated

with the arrow keys) speaks for

itself, it is used to adjust the speed.

The small window above the slider

indicates the selected speed.

The purpose of the button below

that is to select the direction of travel

(toggle function). A marginal note is

in order here. At certain loco speeds,

this button will cause instant rever-

sal of speed. At higher speeds

(approximately speed level 7 and up)

this abrupt reversal is disabled, per-

haps for the wellbeing of potential

model railway passengers. In this

case, the speed must first be

reduced to a lower value, or zero,

before carrying out the reversal of

direction.

The tick box at the bottom is used

to enable or disable the control. The

response time of the system is faster

when fewer controls are active.

The button ‘Save Settings’ saves

the configuration of the active con-

trols in the ﬁle mrkln01.ini , which is

in the same directory as the one from

which the program was started.

Note that the current position of the

loco control is not stored. The stop

button (also operable by hitting the

space bar) immediately forces all

controls to zero. In contrast with the

stop button on the PCB, this stop

function will maintain power to the

rails.

A number of functions, including

which parallel port to use (LPT1: or

LPT2:) are fixed in the file

mrkln01.ini . The details are

explained in the box titled ‘Software

Operation’.

Construction

With the aid of the component overlay and

the layout of the single sided PCB ( Figure 4 ),

you will not need to resort to witchcraft in

order to build a functional circuit. A few con-

struction hints, though.

There is a single wire link just above IC4.

The trimmed-off part of a lead from C1, C2 or

C3 may be used for this. Use this in prefer-

ence to a lead from one of the resistors, since

COMPONENTS LIST

5 5 watts

R5,R6 = 10k Ω

R7 = 2k

Ω

R8 = 4x10k Ω SIL9 array, 1 common

R9 = 22k

Ω

R10 = 47k Ω

R11 = 8x10k

Ω

SIL9 array, 1 common

Capacitors:

C1,C2 = 2200µF 40V radial

or C3 = 4700µF 35V axial

C4 = 220nF MKT

C5,C6 = 15nF MKT

C7 = 10µF 16V

C8 = 1nF MKT

C9 = 10nF

C10,C11 = 100nF ceramic

CON1

C10

Semiconductors:

B1 = KBPC601 (6A bridge, International

Rectiﬁer)

D1 = LED, red, 3 mm

D2 = LED, green, 3 mm

D3 = zener diode 5V6 400mW

T1,T2,T3 = BC547B

IC1 = L6203 (ST Microelectronics)

IC2 = 4001

IC3 = ULN2803A

IC4 = MC145026 (Motorola)

C11

B R

R11

JP1

000066-1

STOP GO

Miscellaneous:

S1,S2 = pushbutton with make contact (e.g.,

Diptronics DTS-6XX)

CON1 = PCB mount 25-way sub-D plug

(male)

JP1 = 3-way SIL pinheader with jumper, or

changeover switch

Heatsinking material for IC1 (e.g. aluminium

bracket, min. thickness 2 mm)

PCB, order code 000066-1 (see Readers

Services

3,5”-inch ﬂoppy disk, Windows control

software, order code 996016-1

Optional:

Power supply transformer, 15 V / 5 A, as an

alternative for the Märklin transformer

Figure 4. PCB layout and component overlay.

10/2000

Elektor Electronics

Resistors:

R1,R2 = 560 Ω

R3,R4 = 1

Ω

GENERAL INTEREST

this one is slightly thicker and the link carries

the entire output current.

The PCB offers the option to use two radial

(upright) electrolytic ﬁlter capacitors (C1 and

C2) or a single axial one. C1 and C2 may both

be 2200 µF. This is sufficient, but larger ones (2

× 3300 µF or 2 × 4700 µF) are permissible and

will also ﬁt. A single axial electrolytic capac-

itor (C3), as used in our prototype, is also a

possibility. The operating voltage was delib-

erately selected to be on the high side (35 V

minimum) to ensure that the circuit will sur-

vive if the Märklin transformer is inadver-

tently switched to direction-reversal.

CON1 is the connector with which the cir-

cuit is connected to the parallel port of a PC.

This may be mounted directly to the PCB.

Take care that the force of plugging or

unplugging the connector is not transferred

to the solder connections. To ensure mechan-

ical strength, there exist connectors with

holes for mounting screws or a kind of barb

for soldering to the PCB. Either type fits. If

you prefer not to connect the circuit directly

to the PC, but position it closer to the railway,

you can use a DB25 extension cable (avail-

able for a small outlay in every computer

store). Alternatively, you can solder the wires

of such a cable directly into the circuit board.

S1 and S2 are switches with momentary

make contacts. The switches speciﬁed in the

parts list fit directly in the PCB. However,

other types may also be used if they are con-

nected with a short length of wire.

A similar story applies to JP1, which

switches the function on or off. Three pins in

a row and a jumper are satisfactory, because

the function is usually switched on. Miniature

PCB mount switches with changeover con-

tacts also exist. Of course, an external switch

attached with hook-up wire is also possible.

The tolerance of C8 is critical, because it

defines the timing. Use an MKT-type

(Siemens or similar) capacitor.

The rectifier bridge (a very common type

from International Rectiﬁer) will, in the event

that maximum output current is demanded,

appreciate a small amount of heatsinking.

Prior to fitting onto the board, insert an M3

bolt in the mounting hole of the bridge (the

screw head is at the bottom of B1). B1 may

now be soldered onto the PCB. Finally, make

a thermal link, using a right-angle section of

aluminium extrusion, to the right angle

heatsink onto which IC4 is mounted (refer to

Figure 5 ). The hole in the bottom of the cir-

cuit board allows access so that the screw

can be tightened. Don’t put the screw

through both the rectiﬁer bridge and the PCB

or you will run the risk that, when tightening

the screw, the circuit board traces get peeled

off the board. Alternatively, you can mount B1

Tabel 1. Loco addresses and train

speed/reversing codes

control

loco address

Delta address

A1-A4

X 0 0 0

0 X 0 0

X X 0 0

0 0 X 0

X 0 X 0

0 X X 0

X X X 0

0 0 0 X

X 0 0 X

0 X 0 X

X X 0 X

0 0 X X

X 0 X X

0 X X X

X X X X

Data bit

Coding

Result

function (lights) off

function (lights) on

A6..A9

0 0 0 0

stop

1 0 0 0

reversing command

0 1 0 0

speed level 1

1 1 0 0

speed level 2 (etc.) …

1 1 1 1

… speed level 14

0 = logic zerol

X = logic open

Figure 5. Construction of the thermal link for the bridge rectiﬁer.

Elektor Electronics

10/2000

GENERAL INTEREST

Software Operation

Naturally, any other 15 V transformer can also

be utilised. From a safety point of view, we

strongly discourage connecting the sec-

ondary windings of different transformers in

parallel.

First check the voltage across C1 and C2

(or C3); this may be 20-25 V at the most. Then

check the logic power supply, for example,

between pin 8 and pin 16 of IC4. This must be

between 4.8 V and 5.2 V; the exact value is

not critical. If everything is in order, then the

entire circuit may be connected to the PC and

the tracks, using the connections B (brown,

outside rails) and R (red, centre rail).

After switching on, the circuit will nor-

mally be in stop-mode. Push the appropriate

button to activate the run-mode. Voltage is

now applied to the tracks. In case of an over-

load, the circuit will automatically switch

itself to stop-mode. Install the soft-

ware by copying the two required files

( mrkln01.exe and mrkln01.ini ) to a directory

of your choice (they must both be in the same

directory). The file mrkln01.ini contains the

definition specifying which printer port the

circuit is connected to. This ﬁle also contains

the text labels for the operating controls.

After starting up the software, the screen will

be as shown in Figure 3 . Operation with a

mouse is self-explanatory, for operation from

the keyboard we refer you to the appropriate

box. If it doesn’t work, check ﬁrst that the

correct printer port (888 = LPT1:, 632 =

LPT2:) is selected in the mrkln01.ini file.

Another possibility is incorrect timing of the

encoder. In this case you will need to tweak

the values of C8 or R9. Those who hunger

for more output power may connect terminals

R and B directly to the input of the EEDTs-

booster. If the tracks are fed only via the

booster, then additional cooling for IC4 and

B1 is not required. A few ground

issues to keep an eye on, particularly if the

EEDTs-booster is connected. Mains earth is

connected through the PC to ground of the

circuit (negative terminals of C1, C2, C3).

Because the output is a full bridge, output B

is NOT connected to mains earth. The R and

B terminals of the EEDTs-booster must be

allowed to ﬂoat with respect to mains earth

and this applies to the entire railway as well.

When connecting (grounded) measuring

equipment this has to be taken into account.

(000066-2)

Key combinations

The program may be operated without using the mouse

(applicable to mrkln01.exe V1.01)

Key (or combination)

result

<TAB>

next loco control

previous loco control

<1>-<9>,<A>-<F>

direct selection of relevant loco control

repeat same key, train reverse

enable / disable relevant loco control

cursor up/down keys

increase / reduce speed

<0>

speed 0, immediately on selected control

<space>

speed 0, immediately on all controls

(software emergency stop)

quit program

Settings in ﬁle mrkln01.ini

The ﬁle mrkln01.ini (residing in the same directory as mrkln01.exe) contains

information on currently used loco controllers (loco addresses), the printer port

used, and the text strings inside the control buttons. Comment not included in

the .ini ﬁle itself is shown to the right.

[PARAMETER]

CH1=0

0 = control not in use

CH2=0

CH3=0

CH4=0

CH5=0

CH6=1

1 = control in use

CH7=0

CH8=0

CH9=0

CH10=0

CH11=0

CH12=1

CH13=0

CH14=0

CH15=0

ADDRESS=888 printer port; 888 = LPT1:, 632 = LPT2

USE_AD=0 not used

SAVE_SETTING_TEXT=save settings text may be edited

EXIT_TEXT=close

to requirement

STOP_TEXT=stop all trains

directly to the heatsink and bend the

connecting leads in a right angle;

they should be long enough.

IC4 is also mounted on the

heatsink. Electrical isolation is not

required (the metal part is connected

to the GND pin), but heat conducting

paste is required. Remember that

none of the AC inputs (K1 and K2)

are connected to ground.

‘power’ is involved.

To be safe, it is always good prac-

tice to check the power supply volt-

age first. Connect the circuit termi-

nals K1 and K2 to a Märklin trans-

former. By initially using the brown

and red terminals (instead of the yel-

low) you can make a cautious start

with a lower voltage.

The standard Märklin transformer

is rated 30 VA. This is too small to

deliver the maximum output current

of 3.5 A. However, actual usage will

indicate if it is sufficient for your nor-

mal use. The 50 VA ‘lighting trans-

former’, with its fixed 16 V output

voltage, may be more appropriate.

Powering up

It is always exciting the see whether

or not the result of your industrious

activity transforms into smoke when

powering up, especially when

10/2000

Elektor Electronics

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