THE BUILDING OF BARNA RAILWAY

"Electrical control and wiring" 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The Barna Railway has a lot of wiring as all the locomotives require track power, the points are controlled remotely and the buildings are illuminated.

 However you don't have to do this to have a great garden railway, there are locomotives that require no track power (live steam or battery powered) and your points can be operated with a flick of a finger so don't be put off by the wiring.

 

Be careful when working on the mains voltage supply and always seek professional advice if your uncertain about anything.

 

Train control systems......

The first thing I needed to do was to decide on the type of control system that I would use to control the trains on the tracks. I had two choices available, the traditional analogue DC system (direct current) or the more modern digital DCC system (digital command control).

 

 "Analogue" DC system (Direct Current)

Analogue controllers work by controlling the supply voltage to the track. This type of train control usually consists of a transformer, to reduce the 240 AC mains voltage to safer level and a control box which controls the speed and direction of the train. The train will increase speed as the voltage is increased and vice versa. To reverse the direction of the train the polarity of the voltage being fed to the track is reversed. This type of control is simple and works well, but having used it for my 00 scale trains I decided not to use it for my garden railway.

There were two reasons for this decision, firstly it can be difficult to control several locomotives independently, there are ways around this but the track needs to be wired up into separate powered circuits with separate controllers and these circuits must be electrically isolated from each other. Secondly, locomotive and carriage lights that are powered from the track will be quite dim at slower speeds because the track voltage will be low.

This is the transformer and speed controller that's supplied with all the LGB starter sets. The 1 Amp transformer steps down the mains voltage from 240v AC  to 20v AC and the speed controller changes the 20v AC to a variable 0-20v DC voltage.

 

I did use this transformer and controller for a short time when I was building the railway. 

 

"Digital" DCC system (Digital Command Control)

The great advantage of using a digital DCC system is the ability to control several locomotives on the same section of track. With the digital DCC system the voltage applied to the track is constant, although no locomotive will move until it receives the correct command to do so. Each locomotive is "chipped" with an onboard digital decoder and is assigned a unique address, this means that several locomotives can operate completely independent of each another. They can even run at different speeds and in different directions.

The other great advantage of the digital system is that lights and other functions like sound and smoke can be turned on and off independently on each locomotive regardless of whether the train is parked in a siding or moving.

As if this wasn't enough the digital DCC system can also be used to control other items on your railway such as points, signals, turntables and reversing loops. I decided not to control my points with DCC, as I like the old switch control panels.

The DCC system used on the Barna Railway is made by LGB. LGB's version is called MTS (multi-train system) and consist of a 6 Amp transformer, the MTS central station and a handheld locomotive remote.

 

The output from the central station is a constant 24v AC supply which is connected to the track. The digital signals are superimposed onto this voltage.

This is the LGB handheld locomotive remote, it communicates with the central station either wirelessly or wired with a long cable.

 

 To move a locomotive you input the loco address (for example "02" for my Stainz) then operate the speed control knob as normal, to switch the lights on and off you press button 9 and pressing button 1 will switch the smoke generator on and off.         

Its important to keep the transformers and controllers, especially the digital DCC equipment, housed in a warm and dry location. The DCC equipment is quite expensive and contains sensitive electronics that may be damaged if left out in a cold damp shed for long periods.   

 

Controlling the points......

There are several ways to operate points on a garden railway, they can be moved manually, pneumatically or electrically. All the points on the Barna Railway are electrically operated by LGB point motors, there are 14 point motors controlled by 11 double-pole/double-throw (DPDT) non-locking (momentary action) toggle switches. The supply to the point motor is only required momentarily until the point has moved after which the toggle should be allowed to spring back into the centre off position. If the supply is not stopped the coil will quickly burn out.

 This drawing shows how the polarity of the 12v DC supply to the motors is reversed when the toggle switch is push up and down.

The control panel has 11 of these DPDT toggle switches, they are divided into three locations, yellow at Barna Station (6 motors), blue at the Kelso Goods Depot (4 motors) and green at the storage sidings (4 motors). Some switches are operating crossovers so there are more point motors than switches.

 

The panel is housed in an outdoor metal post box with a lockable front door. 

This image shows the inside of the control panel, the three strip connectors are where the 12 core cables (6 twisted pairs), from the three locations, are terminated.

 

The orange wires go into these connectors to supply the 12v DC to the individual motors. 12v is more than enough voltage to move the points and I wouldn't recommend using any more than this.

 

Illuminating the buildings and structures......

At night the buildings and structures on the Barna Railway are illuminated. I installed a 12v DC ring circuit using 1.5sq twin and earth cable, this cable follows the track work around the railway, this enables me to get a 12v supply to any location on the railway. There are a number of options available for illuminating buildings, from small filament bulbs, grain of rice bulbs, or LED's. Personally I prefer to use small 12v miniature bayonet cap filaments bulbs (MBC tubular R10) as I like the warm glow produced from the incandescent light. I have fixed bulb holders (Ba9s) in each building, so the bulbs can be easily replaced. The images below show the type of bulb and holder used and the resulting effect at night.  

I have also used some LED's for the buffer block lamps and illuminating the bridge. When working with LED's there are two important things to remember.

Firstly, never connect them directly to a battery or power supply, an LED must have a resistor connected in series with it to limit the current passing through it. For example, a standard (2.5v 25mA) LED powered from a 12v supply would require a 470 Ohm 1/2 watt current limiting resistor.

You can buy 12v LED's that have the current limiting resistor built into them.

The second thing to remember is the polarity, LED's must be connected to the power supply the right way. The longest pin is the positive (anode) and the shortest pin is the negative (cathode).

If the pins are cut the same length then the negative pin is on the flat side of the LED epoxy lens/case.   

To illuminate the bridge I used three sets of 12v mini spot lights designed to light up the inside of a car. Each set has three blue LED's which can be moved around on a plastic base plate. There not designed to be used outside so I made them waterproof with some epoxy resin. The pictures below show one of these sets secured to the edging stones on the pond at the bridge illuminated at night.

 

Click on the contact me link if you have any questions or comments.

 

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