Sunday 14 November 2010

The train on line 1 is running itself....

A long time since the last posting, but here is a train one...

For the Warley show this year, I will have a demonstration on DCC and 2mm scale topics. This will include some basic issues, such as how to fit decoders in limited space, and some more advanced topics, such as train detection, interlocking, and automation.

The advanced topics are illustrated with a simple track arrangement which can be run automatically or manually. A fairly rough video is shown below (bring back the old version of Windows Movie Editor, it was easier than the current one !).

The automated shunting sequence includes careful buffing up to the train, and if the loco running has lights, these are switched on/off at appropriate times.

The train detection is through MERG DTC-8 detectors which register current in a track section. Those feed their output to a HDL LocoIO board, which places the information on a LocoNet network. From the network, information is picked up by other LocoIO boards (displays status on LEDs, etc), and via a computer interface, to JMRI. The LocoIO boards also provide input from the manual lever frame, and output to LED signals at the trackside and servo motor drivers to move turnouts.

JMRI provides the interlocking for the signals rules, an on-screen duplicate of the lever frame, and the automation scripts which send instructions to run trains, change signals and turnouts, alter functions on trains, etc.. The scripts respond to the state of the track detectors. JMRI can track a named train around the system, so it is known which train is in which section.

Train movement comes from a Digitrax Zephyr command station, which relays instructions from LocoNet to the track. It also offers the manual running controller.

A second manual handset, a Uhlenbrock Fred, provides a hand-held controller.

And, if any visitors turn up with an iPhone with the WiThrottle Application loaded, they are welcome to connect it into the system and drive the trains on their iPhone.

Sunday 11 April 2010

Skiing; Skarheimen 2010

(With apologies to those looking for model railways; fair chance the next posting will be on model making...)

A hut-to hut tour through Skarheimen, March 2010. Weather mixed, good some days (hence pictures!), poor others.

Arriving at the first hut, staffed.

Start of long day climbing a 1750m peak.

Peak appears through light cloud...

Further up, peak is immediately above skiiers, still nearly 2hrs until the top. One to right heavily corniced.

View from the top; lake is around 800m below, mountain in far distance perhaps 70km away.

Unstaffed hut; home for two nights.

Staffed hut under spectacular rock edge. But weather not good !

Journey's end, the road in the valley with a bus stop !

Skiing; Kvitavatn 2010

Early February 2010, possibly the best weather I have ever had skiing in mountains; whole week of sunshine, good visibility and only one windy day. Long days of up to 25km and 1000m of climbing - no ski lifts if you want to get into the wilderness !

Wednesday 27 January 2010

Using six outputs on Zimo MX620

I have a 2mm scale Class 24 diesel, fitted with a Zimo MX620. I wish to use all six of the outputs on the chip to drive various features; independent lights, working couplings, and I might use the last output for a cab light.

The standard Farish 24 comes with a circuit board for a six-pin (2 function) decoder, and took up all the top of the chassis. This has the lights paired front and back. So the board was replaced. I'll post a sketch of those new boards later, their main feature is a 2.2Kohm resistor on each function output to control the current to the LED lights at each end.

The Zimo MX620 has six function outputs. Four are normal 12v full current, and two are "logic level". Two of the normal outputs are on the wiring harness (or pins), and all the others are on solder pads at the other end of the chip (along with a "ground" or 0v, and another 12v (or blue) pad). The outputs Fo3 and F04 are enabled by a CV change; they have a lot of capabilities; Susi sound data output, Servo driver or normal function output.

The logic outputs are about 5v, and could drive a very small current LED. But, the wiring of the lamps in the class 24 make it difficult to connect; they are wired for a common positive supply.
So, it was necessary to make F03 and F04 drive a normal output. This can be done several ways, but this simple transistor circuit does the job nicely:

The only additions to the normal connection to a function output is the transistor, the 50Kohm resistor, and the connection back to the Ground Pad on the decoder.

In my case, I used the track pickup (decoder red wire) to provide the positive supply. I had to attach wires to the solder pads for ground and the Function output.

I built the circuit twice; once with big parts and using long leads from loco to a test board. The second circuit (used in the loco for real) is a few square mm of 0.3mm PCB with surface mount resistors, and transistor laying on its side with legs cut very short. Check all the resistances, etc. before hooking up to the decoder !