Sunday, 9 September 2012

DCC Dabbling

The garden railway has now extended significantly in both directions, and from the only control point, which is roughly in the centre, it is not possible to see both ends. This makes operation difficult and detracts from the enjoyment of "watching the trains". I considered several solutions, and decided that the best solution would be one providing wireless controllers capable of operation along the full present and future route of the railway.

The "preferred solution" selected for trials was DCC, using the NCE Powercab controller with USB interface to a computer running JMRI Panel Pro software, and communicating wirelessly with a mobile device running WiThrottle software.

The first picture below shows the set-up in the summer-house. The Powercab and its power distribution panel are on the left, the laptop computer is running JMRI, and is hiding the small USB interface card. The three software packages (the USB driver, the JMRI control software and the WiThrottle application) were all downloaded free of charge via the internet.

For my existing DC control system, the summer-house is home for a mains transformer with a 16V AC outpot. This is taken by buried cable to a weatherproof box on a tree, containing a DIN socket compatible with Gaugemaster DC controllers, the 0-12V output going back down the tree to the track. For the DCC trial, the cable was unplugged from the transformer and connected to the DCC controller track output. A DIN plug was made up with two links to link the summerhouse cable to the track cable, and plugged in to the weatherproof box. Using this approach, the railway can switch between DC and DCC control with the minimum of effort.

The Power-cab controller and laptop running JMRI.
The WiThrottle user interface on an ipad.
The WiThrottle application can be run on the Apple iPod, iPhone or iPad, and probably other manufacturers' mobile devices. There is a free version which provides all the necessary functions; and a full version for £6.99 which provides some extra useful features. The picture above shows the two-loco controller from the full version, running on an iPad.

For communication between the mobile device and the main computer, a WiFi signal is necessary. As our railway is at the far end of a long garden, a WiFi extender was needed. This is a simple device which sits in a bedroom window overlooking the garden, receives the current home WiFi signals, and re-transmits them across the garden.

For the trial, two DCC-fitted locos were used, a Bachmann N class and a Bachmann sound-fitted class 37 diesel. The trials procedure was to "play trains", and see what happened!

A DCC-fitted N class. (The smoke was added later.)

A class 37 fitted with DCC and sound.

The trial continued into the night!
The main observations were:
  • It works!!!! "Playing trains" is now much more fun!
  • The WiFi signal suffers local nulls where control is temporarily lost. The effect of this can be minimised by remembering the weak-signal spots (usually behind trees or sheds), keeping the mobile device moving, and not leaving commands to the last monent.
  • Getting all the devices to talk to each other is trouble-free when switching on from cold. It's not so straightforward to regain control if it is lost in the course of the day. But it gets easier with experience!
  • Note that only certain functions of the fixed and mobile computers are used, so it may be possible to use "broken" equipment which would otherwise be destined for scrap.
  • The horn on the sound-fitted loco only works if the loco is moving slowly or not at all. Otherwise, it makes a long broken sound, during which the loco slows down dramatically. Sounds as if horn + engine sound + motor = more than controller's current capacity, but it shouldn't be. I need to investigate.

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