Train Depot DCC

• Introduction
• Project Progress Report
• Encoder Design

It stands for Digital Command Control and it's a NMRA Standard for controlling model trains.

What's so cool about DCC?

• A locomotive can be controlled wherever it happens to be on the layout.
• Multiple trains can be controlled without having to worry about switching points correctly and isolating sections from each other.
• Forwards is always forwards and backwards is always backwards, it doesn't matter which way round you place a locomotive on the track it knows which way is forward.
• There is permanent power to the track which means lights can be always on regardless of the train's speed.
• Extra functions on the train can be controlled such as switching on the headlights or starting a snow-blower!
• Accessory decoders can be attached to the track anywhere which means you can operate electric point motors remotely without having to run wires everywhere.
• You can cause head-on collisions!

Can DCC be used with LEGO Trains?

Yes and no. The main problem with commercially available DCC systems is that they are designed for 12V systems whereas LEGO trains are 9V. 12V would most likely fry a LEGO motor. It might be possible to program a commercial decoder to limit the maximum speed but this isn't something I've investigated.

There is very little room inside a LEGO train motor but having taken one apart there does appear to be enough room to install an N-Gauge decoder.

Partially completed N-Scale decoder

How about building a custom DCC System for LEGO Trains?

Well that's what I've been working on. It's a long way from completion but I've made significant progress. In this mockup you can see what the system will look like. The large black box is the encoder and has two unmodified LEGO train controllers attached to it (up to 4 are possible with this box). Note the red "panic" button used to avert disasters such as an imminent head-on collision.

The encoder runs in two modes, slave mode and master mode. In slave mode it is attached to a PC via the parallel port and a Windows 95 program controls the trains, you can then use the mouse, keyboard or the LEGO train controllers for speed control. In master mode, the PC is disconnected and only the LEGO train controllers can be used.

Here is the encoder control board and an inside view of the box.

I have built a prototype decoder inside a 9V battery box. This has enabled me to make a few hardware modifications and also lets me attach a programming cable to make some firmware modifications. The changes I have made are mainly to allow the train motor to continue to work on a non-DCC layout.

This type of decoder can also be used as an accessory decoder for controlling point motors as seen in this picture. Note how the decoder gets its power (and DCC signal) from the track.