Monday 3 September 2007

Some thoughts on starting small in DCC

DCC seems to be a hot topic at the moment, and after the recent Darkest Essex DCC night, I was finally convinced to let go of my Zero-1 related grudge, and give command control another try after 25 years.

One of the most offputting aspects for me was the bewildering array of command stations, boosters and handsets which, when connected together either in one box or several, consitute a “controller” in the traditional sense of the word. The trouble is, the more you talk to a DCC enthusiast about the options, the more capability you're convinced you need, and the cost of getting started seems to rise.

Strangely, I’m not interested in driving 10 trains at once, or having umpteen people drive my layout at the same time. Nor do I wish to have computer controlled signalling or route setting or any of the other “wow factors” that manufacturers use to try to sell their systems. With a yard of track and two points, that all seems a bit over the top.

From my 2mm “small shunting layout” perspective, the main advantage of DCC is in vastly improved controlability of one loco at once. This is achieved firstly by the constant full voltage high frequency signal on the tracks, which acts to overcome some of the pick-up problems associated with almost weightless mechanisms and the very low DC voltages required to turn modern motors slowly. Beyond the improved track-wheel interface, you then arrive at the “chip”, which is in effect the most advanced electronic controller you can buy, and which can be tuned to the characteristics of each individual loco. You can set the starting and maximum speeds, and even adjust the characteristics of the chip’s high frequency pulse width modulated output to the motor according to its type.

In order to achieve this fine tuning of the DCC chip (or Decoder, to use the correct term) you need to be able to program it. This is where some of the really expensive systems compete – not in terms of how many locos they can control at once, or how many different manufacturers handsets you can connect, or even whether they will do the washing up and mow the lawn – but in terms of programming capability. Unfortunately, however, it seems that when it comes to programming, they are all variations on a theme of trying to set the video recorder. Blindfold. With chopsticks.

After seeing a demo at an exhibition, I realised that programming the chip can be made much more straightforward if done via a computer (assuming you have one, but cheap laptops are nearly as cheap as expensive DCC systems now!), a little box of magic called SPROG, and some free software, DecoderPro. This gives a nice Windows interface to the decoder’s settings. Of course, you still need to understand what it is your’re setting, but at least the job of setting it is straightforward. Even better than that, a SPROG is much less expensive to buy than standalone “DCC Programmers” resembling TV mutant remote controls, or the command stations with similarly frightening interfaces and capabilities.

So having decided I did not need a fancy control system to do the programming, and I only want to drive one of a very few locos at once, all I really wanted was a box with a speed knob on it (and not much else) that would behave in the traditional manner. I was pleasantly surprised therefore to find that there are some entry-level systems which can be had for a bargain price and do everything I want. The beauty of the DCC system is that the command signals which go onto the track must conform to the NMRA standard. This means that whatever control system you buy, its output (so far as instructing particular trains to move in particular directions at particular speeds is concerned) should be the same… so there is no real “quality” issue here. Remember that it is the decoder chip that is really the “controller” driving the locomotive’s motor, and all decoders understand the same NMRA language. inertia, feedback, load compensation, acceleration and braking characteristics, etc. are all programmed into the chip. It is therefore worth spending a bit more money on a decent decoder if you want these features. It is effectively giving your loco it’s own on-board pentroller.

I found that the Bachmann E-Z Command system fitted the bill perfectly for me. It is a command station, booster and throttle built into one small box. It only allows up to 10 locomotive addresses, but if I ever build more than 10 locos (unlikely within my lifetime at the current rate!) there’s nothing to prevent me doubling up addresses so long as I don’t have two locos on the layaout at once (again, unlikely for my layout). It’s power output is enough to drive 2 locos on the track at the same time – so already double my requirements. The best thing of all about this system is that your local model railway shop will probably sell you one split from a train set for around £35. You can pay a lot more for one in a cardboard box rather than a recycled Morrisons carrier bag if you wish, but think of the environment! As far as quality and compatibility are concerned, Lenz designed this system for Bachmann, so I expect no problems.

My message really is this: DCC is not just for large club layouts. Furthermore, if you want to dip a toe into the murky waters of DCC, you can do so for not much more than £100: A SPROG (£50), an E-Z Command (£35) and a decent small decoder like the Lenz Silver Mini (£25) are all you need to experience the full richness of improved control. Once you’ve seen the difference “chipping” a loco can make, you’ll be hooked. Even if you’re then seduced by the sales literature, and decide you want an “american basement” style wurlitzer of a layout in ready-to-run N gauge, only the E-Z command unit will have to attempt to recoup its cost on e-Bay.

1 comment:

Anonymous said...

Nick: Thanks for the easy to read / understand description of DCC. I am sure it will inspire some to follow your lead, maybe even me one day.