NN DCC Controller

Nick and Nigel present their new DIY low cost simple DCC control handset.

The first model was successfully tested on 4th March.

The NN handset connects to a modified Bachmann E-Z DCC command station. The handset has speed (rotary knob) and direction control (two red buttons) of a locomotive selected on the DCC command station. Function selection is on the DCC command station.

The handset automatically takes over control of the locomotive selected on the Bachmann E-Z when plugged in. Control reverts back to the E-Z when the handset is disconnected. It is possible to wire a layout with a series of sockets in convinient locations, and move the handset between sockets.

The design is deliberately minimalist; many layouts are small with only a handful of locomotives, and a simple control is often the most appropriate option.

If running a layout with only one or two locomotives moving at a time, from a total fleet of less than ten, the E-Z is an ideal command station: Its cheap (£35-£40), compliant with standards(*) and very easy to operate. The weakness is a lack of hand-held controller - the E-Z is too big and gets a bit warm to hold in the hand - hence our addition.

Our handset case could be a lot smaller smaller; we selected this size as a good fit and weight distribution when held in the hand.

The changes inside the Bachmann E-Z require insertion of a few wires, a relay, capacitor, resistor and removing the original "expansion" socket. All are careful soldering jobs rather than reprogramming digital electronics. We'll publish a description of what goes where later.

Total control system cost is well under £50 - the Bachmann E-Z can be bought for around £35, and the additional components are very cheap.

For programming the locomotive DCC chips we suggest a Sprog (£50) connected to a computer and the JMRI software toolkit. Total system cost much lower than most other alternatives, can do all programming tasks (including reading back CV values, identifying decoders) and is far easier to use than programming via a DCC command station.

(*) Footnote, April 2008. We have identified another weakness in the E-Z; it appears to only issue 28 speed steps as the control knob is moved, rather than 128 descrete steps. We've checked this on three E-Z units, including one were we had not opened the case(!), and its completely consistent behaviour. The relatively low number of steps means a locomotive can appear to "notch" up the speed range. With careful decoder programming of inertia (acceleration/deceleration) and use of "half speed" F3 function (most chips support half-speed) when appropriate, this can be masked. But I (Nigel) find it annoying that I cannot make the smallest speed changes. We've been told that this weakness is also present in the original Roco LokMaus handsets, so it looks like its common in budget price trainset controllers. I will see over the next few months whether the notchy control is really annoying and if I will need to upgrade the E-Z to something with proper 128 steps; I know I can fit a similar minimalist handset to a Digitrax Zephyr using its "jump ports", though the basic Zephyr will cost at least 3 times as much as the E-Z.