If you are a model railway enthusiast you probably already know about the current trends in model railways, with Digital Command Control or DCC being the standard control system of today. A beginner’s guide to the DCC standard was published in the February 2012 issue of SILICON CHIP.
The advantage of DCC is that many model trains can be run on the same layout at the same time and all under individual control. In fact, many of the DCC systems available today can control or address up to 9999 trains and peripherals at the same time.
Apart from being able to address so many locos and peripherals, DCC greatly simplifies the wiring to model railways. There is no need to have umpteen hundreds of wires going to points, lights, track blocks etc. Since the whole system can be regarded as a serial bus (much like Ethernet or USB), you need only connect a pair of wires to every device and the individually-addressable DCC decoders take care of everything.
Given that a DCC system can handle such a huge number of model locomotives and other equipment, you might wonder how much current a typical system needs to deliver. The current requirement for DCC locos varies wildly. If the loco is large, with a sound decoder and a smoke generator (in the case of a steam loco), then the current required may be 1A or more. On the other hand, a small shunting loco may require less than 200mA. All of which makes it difficult to calculate the current requirements of any layout.
To give an extreme example, on a recent trip to a large model train layout the author noticed that the layout used a huge power supply. I asked the club techo and he said it was an 18V DC power supply capable of supplying 60A; that’s 1080 watts! The supply was fitted with voltage and current meters. At the time, the current meter was showing the total layout load to be 32A.
I was a bit shocked at this but was informed that the DCC system was running more than 25 locomotives, all fitted with sound decoders and some with smoke, right at that moment. At the same time, it was powering a lot of lighting with in excess of 80 lamps and signal LEDs. As well, all the point decoders were powered from the DCC system.
Incidentally, he told me that the power supply often runs for hours at this level yet uses only two small computer fans for cooling. That’s what I call design efficiency!
But even if you’re not running a large DCC layout you will quickly find that you run up against the limits of typical DCC command (base) stations. Some low-cost systems can only supply 1A while the higher priced systems can typically supply 3-4A.
The only way to get more current capacity is to add a DCC booster. The problem with most boosters is the cost. A well-known brand of DCC booster supplying 5A costs around $200. Other boosters rated at only 3-4A cost well over the $100 mark. But let’s be serious, if you want a booster, you don’t want a flyweight; you want a BOOSTER!
The booster presented here can supply up to 10A and you can build it for a fraction of the cost of commercial boosters. It has been tested on several brands of DCC system and it operated without any problems. It is fully compatible with NMRA (National Model Railway Association) standards for DCC systems and so should operate with all systems that conform to the NMRA standards. Incidentally, you can view these standards and many more on the NMRA web site: www.nmra.org
As presented, our DCC booster is a PCB module measuring 127 x 77mm. It will need to be housed in a suitable case but it does not require any heatsinks or fan cooling. It needs to be teamed with a DC power supply capable of delivering 16-18V and 10A.
The booster module has six LEDs to indicate its status and a piezo beeper which can sound a number of alarms if fault conditions occur on the layout.