Power & Control : Introduction
Power & Control : Introduction
The roadbed is now completed, and the track laid so you are ready to implement the next stage by energising your layout and accessories. Indeed, you will have already given some thought to this aspect when you incorporated suitable channels for any wiring you might need under and alongside the trackbed - right? Oh dear – never mind. I laid my track without making provision for cabling, but it is easily remedied. Unless you intend to run live steam, you will probably need to rely on some form of electricity to power your trains or operate any accessories even if in battery form. Household mains power, used incorrectly can have fatal consequences so take extreme care. Keep the power supply dry and out of the weather. Water can cause short circuits, component failure, and may electrocute you, your children, or your dog!!!
Electricity and water do not mix without causing drastic consequences. Outdoors it is vital to take special care that any installation is safe. The general rule is to keep mains voltages (around 230v AC in the UK and 120v AC in the USA) out of the garden altogether to avoid potentially fatal accidents. If in doubt consult a qualified electrician.
The majority of model trains designed to run in a garden environment run off direct current (abbreviated to DC and also often referred to as Analogue (UK) or Analog (USA ) derived from the Greek word analogos meaning "proportional".)
It is possible to use re-chargeable batteries for this purpose - especially if you intend to use Radio Control (RC) but in the main household alternating current (AC) is "stepped down" and converted to a much lower DC output of between 0 and 24v.
Now, I have to admit than when it comes to anything involving electricity, I am probably the least knowledgeable person to give advice. You could say that I am “electrically challenged” so my first thought was to find an expert who could write this section for me as in the interests of providing a comprehensive guide to garden railways the subject simply cannot be avoided.
But then I reflected on all the advice I have read from people who are truly knowledgeable about the subject and came to the conclusion that this might be the wrong approach as I invariably left somewhat baffled and often totally perplexed by their dissertations. Experts, by their very nature, are often totally immersed in their subject matter and so conversant with its intricacies that they find it difficult to convey their undoubted knowledge to lesser mortals in a simple form.
I am sure that there are a few exceptions, but it is hard to find these luminaries.
I even resorted to consulting number of picture books on the subject intended for young children to see if these could help me with my quest but failed to find the right means to convey the information.
In the end I decided to write the module myself whilst envisaging that a beginner in the hobby is unlikely to possess a great degree of knowledge on the subject and try to explain everything so simply that even I could understand.
I shall endeavour to cover only those topics that are particularly relevant to large-scale model railways rather than digressing into all manner of side issues and matters that might be useful to know but are not essential to get your railway up and running. You can always find out about these elements later on if you have a mind to.
If you are already a practised exponent in the incomprehensible world of electricity you may wish to go directly to the next module. On the other hand, I would be most grateful if you could find the time read through this section and let me know where g or might convey a topic more cogently and without obfuscation. Suggested corrections and improvements are always welcome.
The problem, as I see it, is that most of these experts are so conversant with their subject that they fail to appreciate how uninformed their readers really are (especially yours truly) and sometime don't communicate insufficiently simple terms that are readily understandable. They invariably start by taking you through the basics of electricity in considerable detail and after a few sentences on amps, ohms, rectifiers, series,VARS, resistance, volts, volt amperes, resistance, capacitance, diodes, and so on, my mind just seems to cloud over.
Basic Terms of Eectricity
Electricity is essentially a form of energy produced by the behaviour of naturally occurring negatively charged, minute atomic particles (called electrons) which only flow in one direction away from a negative charge (such as a power source) towards a positive one. (Remember your school day physics: Opposite charges always attract each other; same charges always oppose each other.)
A steady flow of electrons around a closed loop or circuit is called current and the flow of energy or force is measured in Amperes (or Amps for short.) Electricity is often compared to the behaviour of water (which tends to flow downhill and follows the path of least resistance?) and is used to power all manner of machines and electrical devices. On a model railway it can be used to power the locomotives, the lights in the passenger coaches, operate points (switches), signals and many other working models or light effects on the layout.
For a fuller explanation of these terms together with "Volts" and "Ohms" I suggest you visit the "How Stuff Works" website by clicking on the button link below:
The vast majority of large-scale model trains manufactured by such firms as LGB, Piko, and Bachmann (including the magnificent K27 pictures above) run on Direct Current (DC) which is also widely used on cars and boats. However, this is not always the case, especially if you have acquired some older locomotives (such as 3-Rail Lionel or Vintage Marx and Hornby Tinplate) so always establish which form of current (DC or AC) will be needed as a mistake here could certainly severely disable your loco but possibly yourself as well.
If you read many articles on operating large-scale trains (and I would strongly recommend that you do) it will not be long before you come across the scary term “Voltage Drop”. These two words conjoined have been something of a bête noire for model railway enthusiasts almost since the hobby moved outdoors and trackwork expanded to fill the space available.
In simple terms "Voltage" is the intensity with which acquiescent electrons are pushed along a conductor or wire. Voltage Drop is the decrease of electrical potential (or capacity) along the path of a current flowing in an electrical circuit. Please take a few moments to absorb this. On DC circuits this is due to the resistance created by materials or components the current passes through. The amount of opposition to the electric current is measured in ‘Ohms’ after the German scientist Georg Ohm. He demonstrated that there were no perfect electrical conductors. Each substance, even the purest of metals, put up some resistance to electric current. The greater the resistance the more volts were needed to “push” the current through.
For large-scale model railways copper or brass (an alloy of copper and zinc) are generally the preferred conductors as these have the lowest resistance, after silver, do not rust or corrode like iron or steel and are easy to draw out into wire or rails. Slide-on brass rail joiners are also a contributing factor as in time they deteriorate and need replacing.
If you can get hold of a copy, I would recommend you to read a series of short articles on “Electricity in the Garden” by Jim Pasha published in the US Garden Railways magazine in successive bi-monthly issues way back in November 1989. In particular the first November – December 1989 edition explains how your choice of rail, rail joiners, the number of track sections, and even the type of motor in your locomotive can have a surprising effect when you add up all the combined resistance generated.
So to recap, resistance is measured in units of ohms (Ω) and is an electrical quantity reflecting how a particular device or material reduces the electric current running through it. Once again, To use the analogy of water flowing through pipes the resistance (or opposing force) is much greater when the pipe gets smaller thus reducing the water flow.
This is much the same behaviour as Ohm identified after observing that a long wire had more resistance than a short wire of the same material. He invented a formula, but I will not bore you with the details as you can easily find it out for yourself.
Somewhat surprisingly, the electrical performance of the rail types commonly used in manufacturing large-scale track show little material difference and have broadly the same values. In the international table of electrical symbols ‘ohm’ is represented by the Greek letter ‘omega’ (Ω):
Brass 0.0015Ω (Code 332 Rail)
Aluminium 0.0018Ω (Code 332 Rail)
Nickel Silver 0.0016Ω (Code 332 Rail)
Further Resistance Candidates on a Model Railway
The good news for model railway enthusiasts ends there. It is now believed that the humble rail joiner is the principle culprit for voltage drop (especially on an extensive railway with hundreds of yards of track – sorry, I still think in terms of ‘old money” so interpret as hundreds of metres) and could each generate quite a significant resistance of around 2 ohms between adjacent track sections, even in ideal conditions. This is because rail joiners don't grip the rail hard enough to form a "gas-tight" connection so air gets inside the joiner and oxidizes the metal over time inhibiting the flow of current.
Thus, if you were to build your layout using only large radius curves and long straight sections you could reasonably expect to experience much less resistance (and thus voltage drop) than if you were to use short curved and straight sectional track involving far more joints. Users of flexible track would gain even more benefit by having fewer connections.
This useful table shows how you can calculate the approximate potential resistance factor for your own layout, viz:
Note: If the layout is in the form of a continuous oval it is likely to be much less - possibly less than 150 ohms. You also need to aware that every length of wire on your railway is also a source of resistance - more in a later Module on "Wiring".
I suspect that these magazines may be long out of print, but Garden Railways publish a DVD-ROM where you can research every issue from 1984 – 2015 and many other useful articles as well. It costs around £80 but is a valuable resource concerning anything to do with large-scale garden trains.
Another useful source of information comes from another long-term associate of Garden Railways, and also editor for many years, by the name of Mark Horowitz. His contributions are always well-written and easily comprehensible and are generally aimed at beginners in the hobby. I will append a reference list at the end of this manual.
Whilst on the subject of reading material I would also recommend, as
does Mark, a book by Andy Sperandeo called “Easy Model Railroad Wiring”
(ISBN 0-89284-0349-2). Once again, the original was published in 1990
so will be hard to find in the printed version (but can still be borrowed
online from the excellent Emergency Internet Archive in the USA) but the
second edition, released in 1999 may still be around. Alternatively, if not
you can currently access (although I am not too sure for how long) a
limited version courtesy of Google’s Archives by clicking the link below:
By all means search for more up-to-date sources but there is no doubt that DC has taken a back seat since the arrival of DCC (Digital Command Control). Initially this trend was adopted by indoor modellers in the smaller scales but it is becoming equally popular with the outdoor railway fraternity and you may eventually succumb to the “dark side” which can prove fun but expensive.
We will examine the most commonly used methods in this module, but Digital Command Control (DCC) is such a ‘game-changer’ that it merits a section all on its own as despite the exhortations to “simply connect two wires” this topic is actually a teensy weensy bit more complicated than that.
If you have already decided that DCC is the way to go by all means skip the rest of this article and proceed at the speed of light using the ‘gismo thing’ link immediately below:
Another reference you might find easier to digest is contained in
"Garden Railway Basics" by Kevin Strong published by Kalmbach
Publications in 2013 (Page 22 in particular).
It won’t have escaped your notice that some of these articles date back to the 1990’s and you may consider them outdated but just remember that DC Control has been around since the 1950’s and is a proven solution that works well. They were also intended for an audience less versed in ‘electronics’ and tailored their narrative accordingly so are far more comprehensible than more modern texts.
Non-DCC Power & Control Options
It is true to say that there are many ways of supplying and controlling power to your trains in a garden environment and each of them have certain advantages and disadvantages. It would be impracticable to describe them all in sufficient depth in this manual, but you will find abridged details for each manufacturer in the mini-modules associated with this Module 21A. Remember, even these are only a guide as the supply market is consistently changing and there is no substitute for undertaking your own detailed research.
I will merely confine myself here to providing a basic overview of the various options available for you to carry out your own investigations and decide what solution is best for you.
So, let us examine the principal options to provide the power element to your garden railway and how you can make best use of them according to your own personal preference and budget.
There is no universal ‘best way’ or ‘right way’ but these are the main choices in no particular order of preference:
Electricity to the Track (DC) - omitting DCC for the moment
Battery (normally linked to Radio Control)
Clockwork (more correctly called spring drive) in this context refers to the mechanism of a device that operates in a similar fashion to a clock utilising a complex series of gears – a technology that dates back to the first-century BC.
A clockwork motor is mechanically powered by a mainspring and a spiral torsion spring of metal ribbon. Energy is stored in the mainspring manually by winding it up, turning a key attached to a ratchet which twists the mainspring tighter. Then the force of the mainspring turns the clockwork's gears, sometimes with the benefit of a governor to control speed, until the stored energy is used up.
Clockwork power goes back a very long way to the dawn of model railways but is something of a rarity these days except amongst owners of old tinplate trains. The first wind-up toys were created in the late 15th Century and mass-produced throughout Europe from the 1880’s by firms such as Märklin, Bing (who also supplied Basset-Lowke and A.W.Gamage) and Hornby who popularised tin-plate model trains for boys.
Many of these vintage trains have survived to the present day and are highly valued by collectors.
It is said to be fairly reliable but due to the lack of control equipment (for adjusting speed and direction) and the difficulty in locating suitable mechanisms I do not propose to cover this method at length. Indeed, control is mostly limited to the number of turns using a key and pulling a lever to start the locomotive in a predetermined direction – it just stops when the power in the spring is exhausted. Some models incorporated levers inside the cab which could be used to set approximate speed and direction or triggers in the track to slow or stop the engine but still not with the precision and flexibility expected of electrically powered models.
The trend declined with the introduction of the small and inexpensive alkaline battery in the 1960s, which allowed motors to run without a wind-up mechanism. Over the next 20 years, wind-up toys lost popularity (information courtesy of Wikipedia).
Unless you have a particular yen to run vintage tin-plate clockwork locomotives and rolling stock, I would recommend that you stick to more contemporary ways of powering your trains. There are numerous sources of information available to the enthusiast and , once again, I will incorporate some reference sources at the end of this section:
The Station Masters Rooms - a retail outlet dedicated to Live Steam O Gauge and Gauge 1 https://thestationmastersrooms.co.uk/Clockwork-Trains
Advocates of live steam say that there is no better way of recreating the semblance of real train operations in the garden and they may have a point. The larger gauge locomotives are sufficiently large enough to accommodate the small efficient boilers and there is much satisfaction to be derived from watching ‘real model trains in action.
This being said live ‘steamers’ still only account for a relatively small proportion of the large-scale fraternity at large but whilst they may lack in numbers, they tend to remain passionately loyal to this form of recreational pastime so there must be something in it.
Unless you intend to move into miniature ‘ride-on’ trains territory most ready-made live steam locomotives come in 32mm (for O Gauge or SM32 track) and 45mm (G45, G1 or G Scale track). Prices range from a few hundred pounds up to quite stratospheric amounts, so it is a good idea to begin with a small starter tank locomotive to gain some experience and certainly visit your local steam enthusiasts club or society for expert advice before making any final decision.
Live steam engines also to run at a constant speed which depends upon the load being pulled and the use of some form of radio control for remote adjustment is advantageous. They have the advantage of being able to run on virtually any track.
Unless you are blessed with the necessary engineering skills and enduring patience to cope with the inevitable trials and tribulations of successful ‘steaming’ however, I rather suspect that it may not be the right path for most of us.
For those who may feel irresistibly drawn to live steam the following references may prove invaluable:
Steam Trains in Your Garden by Brian Wilson
There are also a number of good books to read on the subject of live-steam model railways:
TEE Publishing are also a specialised supplier of such reading material.
Camden Miniatures Steam Services also carry a wide selection of relevant books.
John Sutton Books & Models Another useful source
With track power the aim is nearly always the same – to deliver a safe regulated and controlled low voltage electrical current to the rail tracks sufficient to power your locomotives and also accessories (such as points, signals) where installed.
Track power is usually the most familiar to most people as it is the default option supplied with the majority of Starter Sets summarised in Module 7, although an increasing number of more expensive train sets now come with more advanced Digital Command Control (DCC).
These sets come with all you need to get everything running using the electrical supply already present in your home. This normally includes some vital equipment since the 230v/240v AC running around our houses (110v – 120v in the USA), cannot be used without first converting it to a much lower and safer voltage (maximum around 18v – 24v) as the mains voltage is far too high and potentially lethal. Alternating current, is called ‘alternating’ because the current flow reverses direction around 60 times a second (or 60 cycles). This is also unsuitable for most modern railway locomotives which need a DC (Direct Current) which only flows in one direction at a time.
We will examine how manufacturers accommodate these requirements later in this section.
It is hardly surprising that most large-scale railway enthusiasts get attached to this solution and may feel that they need look no further apart from perhaps increasing the current rating of their control equipment as their layout expands or making the change to DCC (Module 22). Indeed, track power is relatively inexpensive and probably more reliable than other methods which might be employed.
Unlike an indoor layout a garden installation is exposed to all manner of fresh challenges which can adversely affect the efficient supply of electricity to the track and consequently the locomotive.
As mentioned above, the majority of G Gauge model locomotives on the market, whether steam, diesel or electric outline, are still powered by 0 – 24 volt DC electric motors (Analogue DC) but in recent years there has been much innovation in the means by which this current (or increasingly a form of Alternating Current AC) is delivered to the engine via the rails.
At the risk of burning more fossil fuels and exacerbating our carbon footprint feeding electricity direct to the track is usually the easiest way to supply power to your trains and the method adopted by the vast majority of garden train manufacturers and hobbyists. For this reason, electrical track power is still the most commonly used solution worldwide but that is not to say that this will remain the case. Recent advances in miniature battery cell technology (examined later) could well make this the chosen direction for the future.
As the locomotives and rolling stock in G Gauge are much heavier than their smaller scale counterparts the voltages required are significantly higher – up to about 24v DC compared with say 12v DC for OO gauge.
The actual method of delivering voltage and current to the track is essentially identical to that you may have encountered in the smaller scales and the basic principles are the same in that the positive current is applied to one rail (usually the outside one) and the negative connected to the other (the inside one) or the other way around if you prefer. It makes no difference to the end result.
ELECTRICAL CONFUSION ?
The electrical current runs from the positive terminal and returns to the negative terminal.
Hang on a minute. You previously told me that electricity is generated by negatively charged electrons running away from a negative power source to a positive one?
Now you seem to be telling me that the reverse is true and that electrons migrate from a positive ‘live’ source to a negative ‘neutral’ one? Which is it? They can't both be true.
Well, apparently they are!
I clearly didn’t pay enough attention to my Physics teacher because I had always assumed that the ‘live’ wire was always coloured red (now blue) and the ‘neutral’ black (now brown) ) and that indicated that current invariably flowed from the live terminal to the neutral. Apparently this is because we tend to automatically associate the word “positive” with “surplus” and “negative” with “deficiency. The customary long established practice for the fuse to be located on the red (for 'stop' dangerous) "live" wire probably didn't help matters.
The colours all changed in 1971 (after I had failed physics ‘O’ level although I don’t think that was the reason for my lack of success as I failed chemistry as well!) when new wiring codes were introduced but this only serves to add to the confusion. (Why do the powers that be meddle in these decisions just as you are getting used to the situation?)
Well, it seems that most of us have all been hoodwinked for all these years and that scientifically both these conflicting interpretations can be accepted as true.
The disclosure, according to author Douglas Krantz, is a rather murky affair :
Electrical Engineers have always maintained that, in an electrical circuit, electricity flows in one direction: out of the positive terminal of a battery and back into the negative terminal.
Electronic Technicians say that electricity actually flows in the other direction: out of the negative terminal of a battery and back into the positive terminal.
How come? It seems that way back in time Benjamin Franklin caused the confusion by having the audacity to publish his findings on static electricity which indicated, contrary to the then established doctrines in the scientific and engineering communities, that electricity did essentially flow from the negative terminal to the positive one.
So as not to upset the well-established concept expounded in all the existing and conflicting literature and textbooks of the day (not to mention the delicate sensibilities of the experts of the day!) and ‘avoid mass pandemonium’ it was apparently decided to “fudge” the issue of electrical flow direction somewhat.
In the absence of a consensus on what “electricity” actually is the term “conventional current” was introduced to describe the flow of electrons from the positive terminal to the negative terminal allowing electrical engineers to continue to use the interpretation that suited them whilst electronic technicians tended to adopt the more recent “electron flow” theory to describe the flow of electrons from the negative terminal to the positive terminal. Thus honour was served on both sides.
As it happens it doesn’t seem to make much difference which practice you adopt as long as you read the ‘correct’ text-books and consistently stick to one method or the other!
To read the illuminating article by Douglas Krantz (and check out reference source material) just click the button link below:
Let us return to the practicalities as I seem to have digressed rather:
GETTING POWER TO THE TRACK
Connecting electrical power to your track (especially a simple oval) is fairly straightforward.
The ‘live’ and ‘return’ wires are traditionally red and black respectively (or red and blue on LGB and Piko clamps; black and white on Bachmann) which seems something of an anomaly considering the changes in domestic wiring codes in recent years.
The conventional approach has been to use household mains power at 230/240v AC in the UK and Europe and 120 volts AC in the USA and other countries, converted to 18-24 DC volts by means of an inline step-down transformer / rectifier (usually referred to as a Power Supply Unit) allowing the appropriate current to be fed to both rails. All equipment must be cased and fully insulated for safety reasons.
In the early days of railway modelling these transformers performed the ‘rectification’ by means of wire-wound rheostats making the units very heavy. These days the conversion is largely achieved by electronic solutions which allows for auxiliary features to be integrated.
The control element is provided either by incorporating a means of selecting direction and speed into the Power Unit itself (becoming what is customarily referred to as a Power Pack) or by connecting a separate Speed Control Unit (Controller or Throttle) in series to change the speed and direction of the locomotive.
Power supplies for model trains are traditionally rated in tems of Volt-Amperes (VA) whereas other electrical devices such as kettles, hair-driers and light bulbs are confusingly in terms of Watts. However, watts and volts are interconnected as Watts are the combination of volts and amps. Thus:
In basic terms and using the hydraulic analogy, volts are similar to pressure and watts are similar to rate.
Understanding the basic concept of rate is key to understanding watts vs. volts.
Speaking to a friend about traveling, one could say that the vehicle covered 65 miles. While this is useful information, it doesn't give a full picture of exactly what just happened.
You may have said that you drove 65 miles, but what's the greater context of this? Did you drive it in about one hour? That's normal and expected. If you drove it in three months, that's a completely different thing. This is where time comes into play.
Time by itself, too, is incomplete data. If you told the friend that you drove for ten hours, the friend might follow up by asking where you drove or how far you drove. Discussing the length of a car trip is an incomplete set of data.
One set of data deals with distance in the physical world; another set deals with time. Instead of juggling two sets of data back and forth, it is much more helpful and convenient to come up with a single number that combines the two. That number is rate.
So, the formula V x A = W is similar to the car trip example; both indicate rate. With the car, that rate is the familiar designation MPH (miles per hour): rate is equal to distance divided by time.
In electrical systems, amperage and voltage are useful sets of information. But wattage is an additional usual body of data because it combines the two to produce an indicator similar to rate or speed.
The Travel Rate Analogy
Both the volts and watts are related to each other. The volt measures the potential differences of supply sources or the voltage of the electrical devices. The symbolic representation of the volt is V. The measurement taken in volts is easier as compared to watts because watts is the product of the two quantity i.e., voltage and current. The watt is represented by W. It measures the power used by the electric devices.
Safety of use is paramount and responsible manufacturers will all have taken great care to ensure that their electrical supply products are safe. In the case of goods traded in the European Economic Area (EEA), the CE Certification mark shown here is an indication that the product conforms to the European Union (EU) safety, health, or environmental requirements. I say an ‘indication’ as unfortunately there are also fake CE markings on products which do not comply such as the ones below (and there seems little to stop anyone fraudulently using the actual designation mark either.)
In the United States of America one needs to look for the “UL” symbol which stands for “Underwriters Laboratories”, a third-party ‘not for profit’ global safety certification organisation that maintains offices in 46 countries. The absence of a ‘UL’ certification does not necessarily mean that the item is unsafe but serves as an indication that the manufacturer takes their responsibilities seriously and has gone to the expense of obtaining an independent certification to that effect.
YOUR SAFETY (AND EVERYONE ELSES)
You know what comes next. It is no use manufacturers, legislatures and independent certification bodies working hard to ensure that the products on sale comply with safety directives if they are misused.
No mains powered equipment should be permanently located in an outdoors environment as the vast majority of products that claim to be ‘waterproof’ or ‘water-resistant’ are not necessarily so. As we all know water and electricity combined together can be fatal or at least seriously damage your health and those closest to you.
None of the products referred to in this manual are intended for outdoor use (with the possible exception of the LGB 52120 controller although the jury is still out on this one).
Power packs in plastic cases can insulate the user from electric shock to some degree but those with metal casings are likely to transmit the power surge to the operator.
By all means if you cannot avoid this situation (say, by locating the mains transformer in a garden shed and only using low voltage equipment outside) make sure that the day is fine and likely to remain so before running any trains. If there is a sudden outburst or shower you may forget to remove your transformer to a safe environment or possibly risk injury attempting to do so.
Why risk your life or someone that is dear to you?
Water is not the only danger. While many power-packs are fitted with fuses, overload detectors, thermal cut-outs, or other form of short-circuit protection, there is no guarantee that these will react in sufficient time to prevent damage to the sophisticated circuitry inside the case or anyone touching the case.
So, let us begin in the customary manner, with a brief explanation of the basics as they apply to model
railways – especially where the locomotive uses electricity from the track for propulsion. Rather than be overwhelmed at the outset by the vast array of electrical terminology I propose to identify the key words and explain their particular relevance to model railways as we go along.
Of course, if you if you have no intention of using electricity to power your layout at all you can skip most of this module altogether.
For additional safety it is always recommended that your transformer / power pack is connected to a mains supply that ‘trips’ and shuts down the current almost immediately. On recently installed fuse boxes you may have the ‘RCD’ already fitted (the example shown alongside has dual RCD’s), or you can install them yourself by installing a plug-in or wire-in RCD (short for Residual Current Detector ) adaptor such as the examples shown here.
Most large-scale locomotives, in common with their smaller scale counterparts, incorporate an electrical motor which relies on DC electrical current (DC = direct current i.e. electrons flowing in the same direction) from a suitable power pack (term for a single unit incorporating a transformer, rectifier, speed and direction controls) finding its way through the wires, rails and rail joiners to the locomotives pick-up wheels (or sometimes sliders) and then returning though a common rail or wire to the power pack. This can be quite a journey and if connections are not sufficiently tight, or the track clean enough, there is likely to be a reduced level of current reaching the engine causing it to underperform (known as "voltage drop") – even the very words can strike fear into any outdoor model railway enthusiast.
Not to worry unduly as there are lots of ways of minimising the effects of this phenomenon which we will come to next.
I think that’s probably enough electrical terminology to be going on with. Let's just examine some of the practical implications.
Check whether your locomotive requires Direct Current (DC) or Alternating Current (AC) to operate.
Just because virtually all run on DC some don’t assume this always to be the case as some don’t
and applying the incorrect power supply could have disastrous consequences – not just to the locomotive
but potentially it’s owner!
An RCD constantly monitors the electric current flowing along a circuit. If it detects electricity flowing down an unintended path, such as through a person who has touched a live part, it will switch the circuit off almost immediately -far quicker than any fuse or circuit-breaker, thereby significantly reducing the risk of death or serious injury
In the USA & Canada the Ground Fault Circuit Interrupter (GFCI) device performs much the same purpose in preventing electrical shocks.
The Power Pack or Control Unit is then itself connected to the track by insulated wires, one to each rail, either by soldering or attaching some means of clip or clamp in order to convey the current to the locomotive. Control units normally make the loco go forward if you turn the control knob to the right and in reverse if you turn in the opposite direction to the left. There is usually a centre “off” position where no current is supplied to the track.
Throttles vary the speed of the locomotive by increasing or decreasing the voltage fed to the onboard motor. On some this may be an up and down movement rather than a rotary knurled wheel, but the principle is the same.
You must always be a bit careful when it comes to polarity so that the locomotive does not travel in the opposite direction to which the controls have been set.
On a DC track powered layout one rail should always be the opposite polarity to the other and this should remain constant throughout to avoid short circuits.
Apparently, railway manufacturers throughout the world have all adhered to a long standing convention about which way is ‘forward’ which ensures that when you put your locomotive on the track and turn on the controller, the train will proceed in one consistent direction.
If the furthest away rail is more positive than the nearest rail, the train moves to your left. Reversing the controller makes the furthest away rail more negative than the nearer rail, therefore the train moves to the right.
Conversely, if the furthest away rail is more negative than the nearest rail the locomotive will move to the right and putting it into reverse will cause the loco to move to the left.
You can easily switch polarity by reversing the two wires to opposite rails so that all of your locomotives respond to the same instruction as the alternative would be chaotic.
On some more expensive locomotives (such as the Bachmann Spectrum range) you can even alter the polarity on the engine itself simply by moving a small switch.
It goes without saying that track power relies on having good firm connections across the entire layout and regular maintenance to ensure good conductivity.
I am indebted to the Eastbank Model Railway Club for the following diagram which explains everything much clearer than the written world. Indeed, if you have any electrical questions or conundrums regarding the hobby their “Short Circuits” webpage is likely to have the answer:
Connecting Up a Simple Circle or Oval of Track
If you acquire a Starter Set it will almost certainly come with instructions telling you how to connect the power supply to the main supply and track itself. The finished arrangement should look something like this:
This arrangement enables you to start running your trains straight away “out of the box” without further ado. Voltage drop is unlikely to present a problem on this continuous layout but for larger railways layouts, with far more rail joiners, you might want to lessen the chance of it happening by feeding the power to the track at several points just to be sure, like this over-simplified example:
The actual number of feeders you install is entirely a matter of personal choice influenced by how much of a problem “voltage drop” is likely to prove now and in the future.
Given the information that the rails, themselves, offer very little resistance it seems reasonable to assume that adding miles of thin copper wiring to all corners of the track is unlikely to be as good at conducting electricity than say, Code 332 brass rail with a much larger cross-section.
However, we have already established that voltage drop is principally caused by the rail joiners and not the type or even necessarily the length of the rail used.
When I first encountered voltage drop I could not initially take on board the concept that a heavy section of Code 332 brass rail could be inferior in conducting electricity than a thin cross-section of copper wire across a joint or even strung around every corner of the layout. Once you grasp that it is the joiners that are the culprit everything falls into place.
It follows that the more joiners you have the worse the problem is likely to be.
If you plan to install long lengths of flexible track you are likely to have fewer problems than if you use short pieces of sectional track due to the extra joints and potential resistance over the same length of track is significantly greater.
For those of a “belt and braces” disposition you may well favour an even more thoroughgoing wiring plan which some aficionados prefer which is to run the power lines alongside either side of the track with frequent feeders every so often. I read of one enthusiast who even connected feeders to every single section of his track via means of two positive and negative bus cables. The figure below demonstrates the principle:
This solution might have seemed distinctly odd and a little "over the top" to railway modellers who had confined themselves to the smaller scales but is now common-place on DCC layouts as we shall see later in Module 24A. As I possibly said elsewhere in this manual there is more than one interpretation of “just two wires”.
Trunk & Branch Feeders
Another variation on this technique (which may use more wire than the trackside bus wire approach in Oval C depending on the nature of your layout) employs the trunk and branch system as shown below:
Incidentally, there is no need to join the red and black wire spurs to the same point on the main trunk as shown in the diagram but in may cut down on the number of junction boxes you need and help with fault finding if necessary.
Whether you bury your wires directly in the ground (not recommended though) or use some form of conduit you will still need to keep an accurate plan of where they are located and which part of the track they serve.
For methods of attaching the wires to the rails please refer to Module ? on Track Laying. Some makes of track (such as Aristo-craft) may even have screw terminals beneath the track sleeper webbing to simplify the task (although you have to remember to do so before you fix your track in place as I discovered only too late!).
The important thing to remember is that there are no rules (apart from those of Physics perhaps) that lay down how you should build your model railway.
Do your research thoroughly, possibly experiment on a small test track before moving on to your “final dream layout” (although it hardly ever is) and always be open to new ideas however bizarre they might seem at first.
Advantages & Disadvantages of Track Power
So, what are the main benefits and drawbacks from utilising track power?
Electricity is generally available in a domestic environment.
The majority of other enthusiasts tend to use electrical power so everyone from the club can come around and run their trains.
Proprietary locomotives can usually be run straight “out-of-the-box”.
You are unlikely to ‘run out’ of electricity unlike battery power.
New DCC concepts make it possible to operate your trains just like on a real railway (but then conventional DC offers this in part).
Electricity can be dangerous when used incorrectly.
Both track and locomotive wheels have to be kept clean and all electrical connections, including those between the rails, kept tight to ensure good conductivity.
Installing copper-based track (such as brass), or similar highly conductive metal, can prove more expensive than using other materials.
Summary: The fact that electricity is still the most popular method of powering garden trains suggests that there is a lot to recommend this solution but DCC is making strong inroads into the traditional DC technique.
Popular Analogue DC Equipment Solutions
In this section I shall only briefly summarise the equipment choices you have for running your trains using electricity – there is far more information on the individual manufacturers’ products available in the associated mini-modules 21A to 21F.
First a few glossary definitions we shall be using:
Polarity: The two directions of current flow, positive (+) and negative (-), or potential in an electrical circuit.
Power Pack: A commercial, sealed, complete unit for powering model trains consisting of a transformer to reduce house voltage to that required for operating the trains, a rectifier to change alternating current to direct current, a rheostat (or electronic equivalent) to vary the voltage applied to the track, and a reversing control switch or dial. May also have additional switches, indicator lamps, etc.(NMRA)
Power Supply: The source of electrical power whether Mains Supply, Transformer, DC Power Supply or in some cases even Battery Power.
Transformer: An electrical device for reducing (‘step-down’) or increasing (‘step-up’) AC voltage. See also Rectifier.
Controller (Throttle or Regulator): An electrical device used to control the speed and direction of a train by means of switches, levers or rotary dials. This is usually by means of a rheostat (or electronic equivalent) which controls the voltage to the track. The lower the voltage, the slower the train will run. The higher the voltage the faster it will run.
Rectifier: A device for changing the current from Alternating Current (AC) to Direct Current (DC) or vice versa. See also Transformer.
Right, let us proceed:
A “Power Pack” not only acts as a ‘step-down transformer’ by scaling down AC household mains voltages to a much lower and safer level but also “converts” this to a stable low-voltage DC (Direct Current) by means of an inbuilt “rectifier” circuit. These processes may be combined in one unit or in separate linked devices.
Some popular examples of both fully insulated cased units and separate component types are illustrated below.
A: Piko Stand Alone basic Analogue Speed / Direction Controller 24v/ 1.6 Amp PK35006
B. Popular LGB Combined Transformer / Controller 50080
C. Gaugemaster Single Track Cased Controller 5 amp 10LGB5F
Bachmann Large Scale Transformer & Controller as separate units :
A typical example of a ‘Power Pack’ comprising separate units is the Piko Basic Analog Throttle 35006 (Max. Input 22 V DC) with matching Weather Resistant Power Supply 35000 (Max. Output 22V DC) and Track Power Clamp 35270 for G Gauge. All have to be purchased separately.
Initially this sort of arrangement is relatively inexpensive and easy to set up. I say relatively as the financial outlay could still be anything between £60 and £500 depending on the size of your layout and the engines you intend to operate.
Using the simple power control equipment supplied with the starter set is typically good value at the outset but they are often cut-down versions of their standard range. There may come a time when more sturdy apparatus may be needed (say if you need to run locomotives with two motors).
If funds are limited, you might also try sourcing second-hand equipment from a reliable source in order to keep the cost down, but I would not normally advocate this route unless you are sure about the provenance of the apparatus and have chance to ‘test run’ it first
Many locomotives available on the market today draw significant additional amounts of current compared with their predecessors, especially if they have two motors, sound, lights, and other ancillaries.
Suppliers may entreat you to upgrade to a “Jumbo” or “Heavy Duty” unit packing 5 or even 10 amps but before you yield to temptation ask yourself, do I really need all this power?
As we have already discovered earlier there is a huge misconception in the model railway industry concerning the “power” of a given controller. For example, a controller rated at 10 amps must be twice as powerful as one delivering only 5 amps – stands to reason?
But if the 10amp version can only manage to deliver 12v at 10amps (a power level of 120 VA) and the competing product pushes out 24v at 5amp (also a power output of 120VA) the 5 amp unit could prove to be the better buy as the performance of many large-scale locomotives is likely to be constrained at only 12v maximum volts.
So how do I determine which power set-up is best for me?
That’s a difficult question to answer as it depends on so many variables as we are about to discover.
As regards a simple starter set (such as those illustrated above) you can usually rely on the manufacturer providing a commensurate power pack that is perfectly adequate for the task of running a train consist of the locomotive and cars around the circle or oval of track included. Some original devices were only rated 0.5 or 0.6 amp (which would still be sufficient to power the Stainz or 0-6-0 locomotives) but are now generally a minimum of 1 amp (sometimes intriguing labelled as 1000mA for no apparent reason other than to give the impression that it is more powerful than it is.) Reminds me of the warning sign that some modellers put on their outdoor layouts DANGER 24,000 MILLIVOLTS! to encourage parents to discourage their children from picking up the trains or touching the track! ).
A 1 amp rated device would provide a maximum current of about 18 Volt Amperes (18 VA) which is fine for a small locomotive (say an LGB 0-4-0 Stainz or Piko 0-6-0 Tank) with a short rake of passenger cars or freight cars.
Once you begin to extend your track (perhaps to also include sidings and passing loop) and add to your collection of rolling stock you are adding greater resistance and also heavier loads which may eventually generate a power demand that your power pack is eventually unable to meet.
Quite when this point will be met depends on individual circumstances but if you upgrade your roster to include a locomotive with two motors it could be reached a lot quicker. Even adding sound, smoke and light functions can be expected to escalate power consumption as they all draw current and whilst the individual incremental draw is probably very small cumulatively they begin to add up.
Even if your power pack has an additional set of terminals providing an AC output (circa 16v AC) for accessories such as points, scenery lighting, signals, etc. these will also be competing for current from the same source.
I am indebted to Greg Warth who publishes the “Building Your Model Railroad” website, for a useful means of calculating the approximate total ampage needed to run your layout based on the estimated amperage draws from large scale railroad equipment, which I would like to share with you. The same information is also featured on Crain's Railway Pages and several other sites so unsure as to who to credit but thank you all.
I have interpolated and modified the template somewhat in this example.
Remember, it is based on the maximum number of trains you intend to operate simultaneously (even if you have a large roster) – probably no more than 2 or 3 at a time unless you have additional operators – and is only a rough guide but in the absence of any helpful supplier input this is probably the best you can do.
Note the impact of grades (inclines) which place a significant strain on the locomotive motor. In the foregoing example, not necessarily typical, you might just get away with a 5 amp power supply, but you would be pushing the unit to its maximum capacity, especially with a long train climbing the grades. This is all hypothetical as in practice, you are unlikely to have three trains surmounting a steep grade at the same time but it usually pays to have a bit of energy in reserve.
Some power supplies are rated by their VA (Volt - Amp or Volt Amperes) or their wattage capacity. The amp rating is found by dividing the VA or watts rating by the maximum output voltage. For example, a power supply with a 90 VA rating is equivalent to 90 /18v or 5 amps.
As hobbyist Greg Elmassian observes even the best power supplies rated at 10 or 15 amps, will usually only deliver 8 or 12 amps, even on a small layout.
A 90 VA power supply will NOT supply 5 amps at 18 volts or 10 amps at 9 volts or any other possible combination which adds up to 90 - the rating is its MAXIMUM, and at 10 volts it could well produce even less amps than it will at 18 volts. Apparently they are deliberately designed this way for safety reasons so as to prevent dangerous spikes occurring.
The simple rule to remember is that increasing the voltage automatically reduces the ampage. Say that your power supply is rated at 18v DC at 5 amps maximum i.e. 90 VA or Watts of power. Thus:
Using 20v output reduces the current capacity to 4.5 amps (5 x 18/20)
Using 22v output reduces the current capacity to 4.1 amps (5 x 18/22)
Using 24v output reduces the current capacity to 3.7 amps (5 x 18/24)
Some manufacturers (such as NCE) are now recommending that you allow 5 amps for each locomotive for DCC systems in large scale regardless of locomotive size of the size of your layout.
With G-scale the computation necessarily involves both voltage settings AND current capacity. The combined values of both is what gives you the power to run larger equipment. NCE point out that most G-scale equipment is now designed to operate at a minimum of 18 volts.
In order to make an informed decision you will need to know the recommended track voltage for your equipment and the total current capacity needed for all locomotives. As already indicated manufacturers do not always make this easy to find, almost as if they are afraid of litigation if they fall short.
Increasing the voltage output reduces the current capacity.
It seems that the majority of modern large scale locomotives will run at realistic (i.e. prototypical) speeds with 10 - 12 volts on the rails providing the track is level. Engines with a heavy trainload may stall on grades unless track voltage is increased slightly - 14 to 16 volts might be needed. Trains with lots of lights, multiple locomotives, or certain decoders will also need a little more voltage as we have already discovered.
Because of internal inadequacies and gradual deterioration due to potential aging over its life, it is prudent to deduct around 10 to 20% from any published maximum rating claimed by the manufacturer to determine whether, or not, you have a big enough power supply for the task in hand.
Components inside power supplies can wear out just like any other or even change value with age, leading to the possibility of high voltage spikes on the track however, hard manufacturers try to prevent such occurences. In some ways older locomotives were probably more robust to cope with these occasional surges but with modern, sophisticated locomotives this is rarely the case. Electical surges are likely to burn out decoders, sound systems and even locomotive motors, leaving you with an expensive repair or replacement bill. If you have any problems or concerns at all, disconnect the power unit and get it properly by a qualified electrician.
Some newer large scale power supplies are capable of generating 24 to 30 volts. Some low-cost and many older locomotives (especially those which have motors rated at 12 volts max) may not survive these high voltages.
The accumulated wisdom is that 50 to 100 actual watts (or 50 – 100 VA or 4.5 to 6 amps) will usually be sufficient to power a train on many home layouts. However, dual motors, traditional whistles and bells, passenger cars illuminated by filament bulbs, exceptionally long trains, etc. can prove taxing for any locomotive so once again why not invest in a power unit that affords you a bit of insurance against the future and saves you money in the long run.
As one expert propounded, why spend many hundreds of pounds on your engine roster and then try to operate them with a cheap, basic, and potentially inadequate electrical power system? Once again why compromise? It would be far safer to build in some redundancy (about 10 – 20% say) and go for a more highly rated power unit if only to cater for future expansion.
I seem to have overloaded you with numbers for which I apologise but hopefully you will be able to extract the data most relevant to yourself and be aware of the situation.
RUNNING ADDITIONAL LOCOMOTIVES
The main problem with DC comes when you wish to run more than one train at a time on the same length of track. This is simply not feasible with an Analogue control which only permits one train on the track at a time without fairly complex modifications.
The solution adopted in the past was (and still is to the present day) to create separate ‘zones’ or “blocks” of track insulated from its neighbour with its own power supply and sectional control equipment, but this often proved complicated to install and liable to produce short-circuits if not installed correctly.
The irritation of track powered lighting automatically going off as soon as the current is switched off also has to be endured unless you resort to fitting battery powered leds in passenger cars etc.
Some manufacturers, notably the much lamented, Aristo-craft, supplied a mobile form of control using a rudimentary form of Radio Frequency (RF) entitled the “Train Engineer”. This entry-level hand-held device had few wires to connect and enabled the operator to change the speed and direction of the locomotive over up to about 300’ distance away provided there were no physical obstructions. More of that later as whilst Aristo-craft are no longer in business the RF side of things is still available at the time of writing from Crest Electronics (recently acquired by Precision RC trading as Revoelectronics just to complicate matters further.)
In some respects the programming and user documentation supplied with the Train Engineer was found wanting by some so George Schreyer penned a very useful webpage containing tips on how to get the best out of this device.
Prior to their demise Aristo-craft also brought out an updated system called “Revolution” which significantly improved on the original Train Engineer but whilst it performed many of the functions of DCC it was still not compatible with the NMRA published DCC standards so must be looked upon as a competing alternative to DCC. This device, which can be used with either track or battery power, has also gone through further development since 2009 and later models introduced sound applications.
For a comprehensive run-down on the “Revolution” we turn once again to Greg Elmassian who has contributed a very detailed analysis of the systems strengths and weaknesses available on his website.
This YouTube Video records a customer’s first time use and initial impressions:
The Ottawa Valley Garden Railway Society website also posts some tips
on the operation of the Revolution TE extensively used by their membership. Drill down on the relevant ‘View Page’ link for more detail including how to install and
You may also come across some older style Analogue DC Control Systems like the following USA Trains Train Power 10. The advice with all these systems is to try before you buy as some of them may have had very heavy usage or be underperforming in some way. On balance I would not recommend buying second-hand power equipment online unless you are able to return if you are unhappy with the equipment for any reason as it is impossible to assess the performance without a practical session. Also make sure that they are suitable for your household mains voltage which differ in different parts of the world. In the UK 230v AC is the norm whereas in the USA most mains circuits are 110v AC and need a step-down-transformer to work in the UK.:
LGB Multi-Train System (MTS)
In around 1995 LGB also introduced their own form of digital remote control using their in - house proprietary Multi-Train System (MTS) developed in association with Massoth. This was essentially a DCC forerunner but with limitations compared with today’s advanced DCC systems capable of controlling up to 256 locomotives, points, lights, sounds, etc.
As previously explained, with conventional analog operation, the motor is powered directly via the tracks. When you turn the throttle knob, the track voltage increases and the loco moves forward or backwards baccording to the setting. If there are two locos on the tracks, both start moving at the same time and in the same direction. To operate several locos at the same time on an analog layout, the layout must be divided into separately powered track blocks. With digital operation and the LGB Multi-Train System, the situation is entirely different. The tracks are always live and carry the maximum voltage. All commands to the loco are relayed in real-time via the tracks. Because of this constant voltage, with some locos you hear minor background noises during certain operating conditions. These noises are sometimes louder with analog locos during “Analog Control” operation than with digitalized locos. A decoder is installed in the loco and controls the motor and other loco functions such as lights and sound.
MTS evolved over the years in a number of generation releases MTS 1, MTS 2, MTS2P and MTS 3 (pictured), which proved successful for a while but as international standards were established for DCC its popularity waned due to problems getting it to work with decoders fitted to other brands of large-scale locomotive. Incidentally, LGB refer to the combined “Command Station” and “Booster” as a ‘Central Station’.
In essence the LGB Multi-Train System, although based around many of the principles of the NMRA "DCC" standard, went a little bit further than the published standard by offering certain additional features, particularly in order to ensure full compatibility with the digital sound systems found in LGB locomotives.
However, MTS, in common with many proprietary control systems developed in the 1970’s and 1980’s, is old technology with MTS1 and MTS2 relying on serial communication as opposed to the faster parallel communications incorporated into DCC.
The third generation LGB MTS III Central Station (LGB 55006) is capable of addressing up to 23 locomotives (0 – 22) but if you substitute the Massoth DiMAX Navigator you can, in theory at least, go up to 10,239 individual loco addresses.
Although possibly cheaper, MTS does not really stand up to comparison with the latest DCC systems available. It has also not been significantly enhanced to any great extent for many years and unless you have already invested significantly in this obsolescent technology it is probably better to move to a more advanced and non-proprietary DCC solution covered in Module 22.
Apparently, you can run an LGB engine equipped with an MTS decoder on the Piko Digital System (actually manufactured by Massoth) but I cannot guarantee this unequivocally so please make your own enquiries if appropriate.
To view the LGB MTS Instruction Manual use this link:
This is a longer, but rather noisy video: