PC-controlled layout to NMRA-DCC standards

Some tips                               Stationary decoder

How does it work?              Block sensor

Winlok 2.1                              Loco- decoders

Booster

If you decide to build a digital system by yourself you will as allways save some money and also have great fun. With basic knowledge in electronics and soldering it is not that complicated. You will find several alternatives in literature on the internet.
Rutger Friberg`s NMRAF- solutions of boosters and stationary decoders is a very good example.
I started to build my layout based on analog technology with block sections and four trottels controlled from a panel with LED's and switches.
I took the first step towards digital control in the beginning of 1996 by looking for  PC-software.

My choice fall on Winlok 2.1 and I started to run the free demo version downloaded from internet. I recommend to define all functions on the layout and run the software in simulation mode to test your ideas before buying or building the digital hardware.
With a large interest of self building and very good instructions from the books of  Rutger Friberg I decided to build the boosters and the stationary decoders. The mobile decoders used are Lenz. I found it to complicated to build loco decoders for the N-scale even if there are some examples using PIC-processors that claims good knowledge in programming and surface mount technology.

The central unit with a trottle (alternatively PC) transmits via a booster a stream of digital pulses to the track. The output includes both power and data.

All mobile loco decoders on the track receives the pulses and decodes the information. Each loco have an individual "address" and only one locomotive responds to the actual address followed by data for loco control. Several locos on the same track can with this technique be individually controlled from the central unit. A rectifier in the mobile decoder separates power for the motor and data for control of various functions in the locomotive.

The NMRA DCC standard defines a long list of functions included in the decoder registers.
Most mobile decoders will only take care of the basic functions in the locomotives.

Forward / Reverse   -    Start level   -   Speed   -    Acceleration   -   Retardation   -    Light on / off

The speed is controlled by 14 to 128 steps depending on type and manufacturer of the decoder.
More advanced functions like smoke, sound and couples can be operated from some decoders or more than one decoder installed in the locomotive. A real challenge for the N-scale model railroader.

The choice of decoder depends on the available space and current for the loco usually not more than 0,5 Amps for the N-scale locos. If you measure the "stall"-current before you install the decoder you will be safe by knowing the maximum loco current for any situation.
Connect a DC-amp instrument between the analogue voltage supply and the track. Hold the loco locked to the track and turn the trottle to maximum and read the current.Don’t forget to add the loco lamp current to obtain the total max current.

You can find suitable N-scale decoders from various vendors.  Lenz, Digitrax, Arnold and others have a good assortment in small size. The new DCC handbook by Rutger Friberg and Stan Ames have a complete list of decoders with all data.
I have used the Lenz LE 030 and 040 with EMF-technology. This facility with feedback of motor load to the drive logic’s in the decoder will keep the loco to a constant speed independent of load from the wagons or going up or downhill.

The PC transmits the pulsed signal from a COM port (RS232) to the NMRAF 8 boosters sending the code and power to NMRAF 5 or LS150 decoders .
The signal from the block sensors indicates if the actual section is occupied or not - connected to a the parallel input board (PIO8255) installed in the PC. The software Winlok 2.1 is prepared with drivers for this board and included functions to indicate the status from this input. The boosters have an overload output also connected to the PIO 8255 so the software can switch off power if a short circuit occurs..

The layout can be easily switched from digital to analogue to give the loco`s not yet modified to digital a chance to show up and still use the ability to be indicated on the PC-screen from the feedback from the block sensors.

" I prefer to run my trains by myself and not let the computer take over"

A limited view of computer technology – it is your decision - manual or automatic.Trottles are available on the PC-screen controlled from the mouse and why not a joystick.

With Winlok 2.1 you design a copy of your track layout on the screen including switches, blocks and signals as active elements bound to real events on your railroad model.

Before you start your train - a route is activated that will define the status of involved switches, blocks and signals. Several routes can be defined simultaneously sharing common tracks and switches with interaction between the trains to different priorities.

The feedback from block sensors indicates the position of the trains indicated on the PC-screen. All active functions can be operated by a mouse click on screen by pointing on individual switches, blocks or routes etc.
Complicated? – No, all functions are defined in a standard Windows environment with straight forward instructions and help menus with the result stored in a database linking all data in a logical scheme.
With above tools you run your layout manually following all events on screen.

Winlok gives you a choice of different levels of complexity. For the more experienced programmer a Pascal-like script language is included to simulate both train engineers and central control of the whole layout in a "ATC"-like fashion. Several trains sharing routes can be automatically operated from the PC.

The locomotives normally include a printed circuit board (PCB) bringing the wheel connections to motor and lamps. Disconnect the motor from the PCB and remove coils, capacitors and the rectifiers to the lamps.(hidden at the lamp connections)

"Mini Gold" decoder  in RC4

RC4 printed circuit board

Alternate installations of bulbs

The DCC central units have a special programming mode and  when running from PC a loco programming routine individual for each software is used. The decoder supplier tells the default setting at delivery and how the parameters can be altered. Test the loco with the default values before any changes.

Give the loco a free unique address. Tandem coupled loco`s are given the same address with individual parameters depending on each locomotives characteristics. The startlevel can differ a lot depending on motor and friction. A certain voltage level is needed to get it moving. Be accurate with 14 run steps avaliable and don't through away lots of steps on a not moving loco. The first step shall be tuned to give a smooth slow start and the rest of the steps distributed up to top speed. Acceleration and retardation is programmed to give a realistic movement - run the test track!
Keep in mind that hundreds of tons don`t stop in 10 meters. 

The DCC technique can be treated as AC (alternating current) giving a lot more tolerance against dirt and oxide. A general problem for the "2R" railroader. Some locomotives without boogies are difficult to run smoothly even with DCC. I have tested tandem coupled locos to extend the connetion to the track. Permanent coupled wagons is another solution to extend the number of contacts to the track.
This method could be the only alternative to modify a Z-scale loco to DCC by having the decoder in a wagon with wires to the motor in the loco.

Steam locomotives with a tender is an excellent example where the decoder can be installed in a coupled unit. The above solutions are just example on individual installation used for small scale locomotives.