Electronics and Wiring for Model Railways E-Book

Andrew Duckworth

• Herausgeber: Crowood
• Kategorie: Lebensstil
• Sprache: Englisch

Seitenzahl: 215

Veröffentlichungsjahr: 2019

Beschreibung

In railway modelling, getting the technical components correct is essential for a realistic-looking layout but, unfortunately, these often present the biggest challenges for the hobbyist. Using his own experience as a railway modeller and electronics engineer, Andrew Duckworth provides a guide suitable for all railway modellers, from beginners to the more experienced. With instructions on how and where to use specialist electronic circuits to enhance your layout, this book will help you to achieve a reasonably sophisticated layout. It provides: an overview of the geometry required for building successful model railways; clear explanations of electronics and electrical components; comparisons of direct control and digital command control (DCC); step-by-step instructions for wiring the track, signals, buildings and lighting; reviews of electrical systems, power supplies, wires and cable, control panels and switches and finally, it covers detection, testing and troubleshooting tips.

Leseprobe

ELECTRONICSAND WIRING

FOR MODEL RAILWAYS

ELECTRONICSAND WIRING

FOR MODEL RAILWAYS

ANDREW DUCKWORTH

First published in 2019 byThe Crowood Press LtdRamsbury, MarlboroughWiltshire SN8 2HR

This e-book first published in 2019

[email protected]

www.crowood.com

© Andrew Duckworth 2019

All rights reserved. This e-book is copyright material and must not be copied, reproduced, transferred, distributed, leased, licensed or publicly performed or used in any way except as specifically permitted in writing by the publishers, as allowed under the terms and conditions under which it was purchased or as strictly permitted by applicable copyright law. Any unauthorised distribution or use of this text may be a direct infringement of the author’s and publisher’s rights, and those responsible may be liable in law accordingly.

British Library Cataloguing-in-Publication DataA catalogue record for this book is available from the British Library.

ISBN 978 1 78500 624 1

CONTENTS

INTRODUCTION

CHAPTER 1:THE LAYOUTCHAPTER 2:ELECTRONIC AND ELECTRICAL COMPONENTS EXPLAINEDCHAPTER 3:ELECTRICAL SYSTEMS AND POWER SUPPLIESCHAPTER 4:WIRE AND CABLESCHAPTER 5:CONTROL PANELSCHAPTER 6:SWITCHESCHAPTER 7:TRACK WIRINGCHAPTER 8:SIGNALSCHAPTER 9:LIGHTING PROJECTSCHAPTER 10:DETECTIONCHAPTER 11:TESTING AND TROUBLESHOOTINGAPPENDIX I:GLOSSARY OF TERMSAPPENDIX II:ELECTRONIC SYMBOLSAPPENDIX III:MODEL RAILWAY TRACK SYMBOLSAPPENDIX IV:CAPACITOR CONVERSION CHARTAPPENDIX V:ENAMELLED COPPER WIRE

INDEX

INTRODUCTION

My love of model railways started way back in 1962 with my grandmother sending me a Hornby OO kit for my twelfth birthday. I lived in Nyasaland (now Malawi) in those days, and this was the time when post used to take about a month to arrive, and parcels took about two months. There were no mobiles – you had to book a telephone call twenty-four hours in advance and it cost a week’s pocket money, or send a telex that was converted in the UK to a telegram, again costing a fortune: so ordering was very difficult. So I resorted to sending requests by post to my grandmother, who would send me parts for my layout three times a year, on my birthday, for the summer holidays, and at Christmas. Over the next four years my first railway grew from a small kit into a large four- by three-metre U-shaped layout. This was, of course, the era when the track was a three-rail system, and all parts were made in metal.

During this period I developed a desire for anything electrical and electronic – although the transistor had only just been invented and there were no integrated circuits, it all fascinated me. After my school years I went to a polytechnic in Johannesburg to do a course in electrical/electronic engineering. On completion of the course and with certificate in hand, I applied for jobs in the UK. In my naïvety I stated that I had a love for model railways, thinking this would help with my job application – little did I know. My first job application I received was from a company in Plymouth called ML Engineering. I flew to the UK to start my working career at the age of twenty-one.

ML Engineering was an American company based in Plymouth, which designed and manufactured electrical systems to electrify British Rail. They designed and manufactured an ‘automatic train detection system’ (AWS), which looked like a big black rectangular box placed between the rails. This sent a signal to the train and back to the signal box, indicating that a train had just passed over it, as shown in Fig. Int.1. The company also manufactured the relay interlocking system between the train detector, the points and the signals – Fig. Int.2.

The relay room for most stations was a two-storey building with the relay room under the signal box, and it had racks of relays. Each relay was interlocked with others, so when a points button was pressed on the mimic panel, dozens of relays had to be in the correct position before the current would pass through them to the point motor. This would also put all the required signals in the correct aspect. This was then put on to a mimic display panel, which replaced the levers in the signal box. In my time with the company I worked on Shenfield, Grantham and Crewe signal systems, converting them to electrical mimic displays with push buttons to control the points and the signals, as shown in Fig. Int.3

Fig. Int.1 Train sensor.

Fig. Int.2 Relay room.COMPETENCY AUSTRALIA

Fig. Int.3 Mimic display signal box.

I remained with ML Engineering until 1976, when I returned to Nyasaland, now Malawi, to set up my own electronic manufacturing company. I was unable to use my knowledge in the new company, so branched out into other electronic products that would sell in that country, such as AM/FM radios, amplifiers and speed detectors. This was when my original model railway system was brought out of mothballs and rebuilt in my new home. By this time things had changed a great deal in the model railway business. It was now time to update my layout to the two-rail system, again a slow process as everything had to be ordered from the UK – but the mail system had improved to seven days, so not so bad.

In 1996 I came back to the UK with model railway system in tow. By this time there were transistors, integrated circuits and microprocessors – some of you may remember the Sinclair ZX80 and ZX81 computers introduced in 1981; also in the eighties came Amstrad computers CPC664 and CPC6128. Although very simple by modern standards, they could be easily programmed to do certain functions, a little like the Arduino and Raspberry Pi, to name a few, of today.

Back to the important bit.

MODEL RAIL GAUGE

There is a difference between gauge and scale. The gauge is the distance between the rails, from the inside of one rail to the inside of the other rail, with trains and rolling stock built for each particular gauge. Scale is the proportion that the size of the model is compared to its real-world equivalent. It is normally expressed as a ratio (1:16 or 1/16) or a size (1in:1ft).

When a model train is scaled down the gauge is not necessarily to scale, but to the nearest standard gauge. This means that you could have two different trains both with the same gauge, but in a slightly different scale. In practice this will be hardly noticeable, but it is worth bearing in mind.

Fig. Int.4 Train size comparison.

How to resize scale models using either a copier or printer

The above table shows how to resize scale models using either a copier or printer: use the table to give the appropriate enlargement or reduction to rescale the drawing.

Find your scale in the table along the top, then scroll down to the desired scale and find out the factor you need to enlarge or reduce. So if, say, I have HO-scale plans that I want to enlarge to O-scale, I run across the top to HO, then down to O scale, and see that I need to enlarge the plans to 181 per cent. If I have O-scale plans that I want to reduce to S-scale, I run across the top to O and down to S, and see I need to reduce the plans to 75 per cent.

DC OR DCC

The instructions sent from the ‘controller’ are to vary the voltage to the track: this either speeds up the locomotive or slows it down. In the old days this was called a ‘reostat’, which simply changed the voltage from 0v to 12v, which in turn caused the locomotive engine to speed up or slow down. Modern speed controllers are called ‘pulse-width modulation’ regulators (PWM). PWM is a modulation technique used to convert a voltage into a pulsing signal. This modulation allows the control of the power supplied to electrical devices, especially to loads such as motors. The pulse-width modulation speed control works by driving the motor with a series of ‘on-off’ pulses and by varying the duty cycle – the fraction of time that the output voltage is ‘on’ compared to when it is ‘off’ – of the pulses while keeping the frequency constant. This will be explained in detail in the Power Supplies section.

The instructions are sent from the ‘controller’ to the decoder on the locomotive, or any other item that has a decoder, by means of digital signals that are superimposed over a constant track voltage. In a DCC system the rails have a constant voltage running through them, as does all ancillary equipment. In this voltage there is a series of pulses that are sent to all the decoders on the layout. Each decoder is programmed to respond to a certain sequence of pulses: when it receives that sequence it actions the equipment. Put simply, you control the locomotive and not the track.

THE DC SYSTEM

The DC system has been in existence since the 1950s, and is probably the most common system used, due to the fact that it has been around for such a long time.

You cannot successfully run two trains on the same track. I say ‘successfully’ because you can run two trains on one track, but the problem is that, depending on the motors and load, they may well catch each other up, because they are both getting the same amount of voltage. There is no way to control them separately. Each track circuit will require its own speed controller, and each junction between tracks will require isolators, otherwise all trains will move in the same direction when power is applied to the track. This is why most points, even today, isolate the straight from the turn out – hence the reason you need to fit shorting clips to existing points to run DCC.

You cannot run interior carriage lights on a DC system as they will go out when the train is stationary, or will dim as the train slows down: you would have to fit a little battery pack inside the carriage. (See Lighting Projects.)

The points, turntables and any ancillary equipment requires a separate power source of 12–16v DC in most cases, and a bank of switches is needed to control these items.

This being said, you can run many trains on a DC system as long as each set of tracks has a separate speed controller. So you could have four circular tracks with a train running on each, with each going at different speeds and directions, and also work a shunting (fiddle) yard at the same time, as long as each is isolated from the other by points of isolating track. This is where your bank of switches comes in, to control the points and isolating track.

PROS AND CONS OF THE DC SYSTEM

Pros:

•It’s been around a long time and is tried and tested

•It requires research if you want to do something out of the ordinary

•It costs less than a DCC

•It is very ‘hands on’

•It is more like the ‘real thing’ if you are ‘in’ to steam locos

Cons:

•There is a mass of wiring under the baseboard

•You have a bank of switches that need to be labelled otherwise there will be chaos

•Each track is almost like a separate system within your layout

THE DCC SYSTEM

The DCC system was first introduced in the 1970s, but it was not very good so did not last long. The next generation has been around since the 1990s. In a DCC system the complete layout is live at 12v DC, and this voltage does not vary; what does vary is the signal, which is ‘piggy-backed’ on the voltage.

Each locomotive, set of points, and every controllable item has a ‘decoder’. Each decoder has a specific address, which you create with the control station. So now the controller knows all the addresses of each locomotive, set of points, and so on. The decoder on the locomotive reads the instruction, checks it is for that loco, and acts on the instruction. This means that you could have more than one train on the same line: you could have one train in the station and another approaching the station, or you could reverse one train on the same line as a train is going forwards.

The fiddle yard can be worked with more than one train at the same time, as long as you have eyes in the back of your head.

The DCC system does away with the banks of switches, and electronic circuits to control this and that. The complete layout can be run from a computer or android with a display of your layout in real time.

This is a very brief description of the two systems; however, there are thousands of pages on the web about both types.

For what it’s worth I am a traditionalist and therefore would go for the DC system. Part of the magic of a model rail system is the fiddling, which never ends with a DC system – you do, however, need a greater knowledge of electricity and electronics.

PROS AND CONS OF THE DCC SYSTEM

Pros:

•A lot less wiring, requires a bus bar and spurs to each piece of equipment (points and so on)

•More control of locomotives and ancillary equipment

•Computer control, therefore you can create complete scenarios of your layout. Most old locomotives can be fitted with a decoder

Cons:

•The major downside is the cost. The average cost of a controller is around £200, though prices are on the way down

•Each locomotive, set of points and so on will cost around £15 for each decoder

•The decoder cost is on top of your normal layout costs

CHAPTER ONE

THE LAYOUT

The layout is a very personal thing, whether it be a simple oval with sidings, or a replica of a real-life railway layout. The next big decision is to go either DC or DCC. A DC system is more commonly referred to as an ‘analogue control system’, where the two rails are powered by a 12-volt DC speed controller, and one rail is the +12v (feed) and the other rail is the 0v (return).

This book concentrates on the DC system; if you are going down the DCC route there are plenty of books on this subject. In a DC system the controller is fed to the rails so that we have one rail as the positive rail (feed), which we will show in this book as red, and one negative rail (return), which we will show as blue. In wiring an analogue layout there are three distinct sections: the track, the points, and all ancillary equipment.

SCALE

The next decision is to decide which scale you are going to work with. In this chapter we show all the model railway scales that are available. Certain manufacturers have track parts that are unique to them, and in some cases they can be used with other manufacturers of the same scale, but care must be taken with the angles of the curves and turnouts. Your first decision is where your layout is going to be housed, and how much room you have available. We have set out below a minimum curve for the most popular scales.

The reason there are two radii in certain scales is due to certain manufacturers having different radii for their layouts. When planning your layout it is important you decide which system you are opting for – you can then decide on the space required. These are the minimum, so if you want more than one curve – for example an inner and outer line – you will need more front-to-back space.

GaugeMinimum radiusG scale609–1,117mmOn3 scale914mmO scale437–607mmS scale508mmHOn3 scale381mmHO scale381–558mmOO scale371mmN scale247mmZ scale195mm

There are plastic stencils available for most scales, which makes it very easy to design your layout on paper first. This is well worth doing, as it should show up any problems you may come across.

It is important to know the track spacing for your scale: if this is not maintained, trains can sideswipe each other at points or on curves.

TRACK SEPARATION

Each scale will have a different parallel track separation. The spacing can be made greater by putting straight rails between the two sets of points. In some cases the spacing may have to be greater on the curves due to the overhang of certain coaches and locomotives. You will need to keep an eye on this, as there are no hard and fast rules. There are templates available for most gauges, or you could make one yourself.

Fig. 1.1 Adjustable track separator.

Fig. 1.2 Homemade track separator.

Fig. 1.3 Track separation.

TRACK JOINING

Most track sections come with a ‘fishplate’ on one rail at each end. These are used to lock each section physically and electrically together. You must ensure that the fishplate has been fitted correctly otherwise one rail will be higher than the other.

Fig. 1.4 Fishplates.HORNBY

WHY IS IT CALLED A FISHPLATE?

A fishplate is a metal bar that is bolted to the ends of two rails to join them together in a track. The name is derived from fish, a wooden bar with a curved profile used to strengthen a ship’s mast. The top and bottom edges are tapered inwards so the device wedges itself between the top and bottom of the rail (which is called the ‘fishing’), when it is bolted into place. In model railways, a fishplate is often a small copper or nickel silver plate that slips on to both rails to provide the functions of maintaining alignment and electrical continuity.

TRACK LENGTH

It is important to remember that track length as quoted by the manufacturer/supplier is the length of the track, and does not include the fishplate joiner.

MEASURING TRACK LENGTH

While you are designing your layout on paper ignore the fishplates; the length of any piece is one end of the rail to the other end of the rail, and this will give a true dimension of your layout.

Fig. 1.5 Joining two tracks.

Fig. 1.6 Track length.

TRAIN AND COACH OVERHANG

As locomotives and coaches go around bends they create overhang and underhang. This means that placing structures and objects too close to the track will cause problems. Please bear in mind this is an average, and certain locos and carriages may have a greater overhang than the average.

Fig. 1.7 shows the overhang and underhang (red) for each of four curve radii. The red lines above and below the black lines (tracks) show the extent of the overhang or underhang. The table shows the distance in mm.

Train overhang and underhang

Curve

Underhang

Overhang

4th radius curve 572mm

8.00mm

7.50mm

3rd radius curve 505mm

8.50mm

8.00mm

2nd radius curve 438mm

9.50mm

9.00mm

1st radius curve 371mm

11.00mm

10.5mm

It must be stressed that these figures are for OO gauge, and will vary depending on the gauge you select.

Fig. 1.7 Overhang and underhang.

TRACK RAMPS

If you are thinking of having dual-level tracks then you will need to create up and down ramps. The main problem here is the ability of the train to go up the ramp, and with how many coaches; the weight of the train is all important, as it needs to create friction with the track – the lighter it is, the more chance you will get wheel spin and go nowhere. A steep rise to 80mm will take up 1,344mm, but should work for most modern-made locomotives; however, a better ramp length would be 1,680mm. Using a Helices ramp will take up less space but will require a slower ascent and descent. Keeping track gradients at 2 per cent or below is a good rule of thumb. It can also look more realistic than a really steep gradient (as long as you have the space). Most manufacturers have their own ramp systems.

Fig. 1.8 Set of plastic ramps.HORNBY

Fig. 1.8b Helices.MODEL RAILWAY BASEBOARDS

BANKING AND TILT

On a model railway layout, super-elevation serves no functional purpose: the weights and forces just don’t work the same way as on the real thing. It’s purely there for visual effect. Elevation (E) between rails will be slightly less than shim height if the shim is directly below the rail, but consistency of placement is more important. Shims should be increased by 0.25mm up to a maximum of 2.5mm – anything above this could cause problems with stationary trains on the curve. Shims should not be used on first and second radius curves.

Fig. 1.9 Virgin train banking at speed.

Fig. 1.10 Shims under the track.

If you want to go down this path you can get a pack of spacers at 0.25mm increments from your local builders’ merchant. They just need to be cut in half to fit under the track.

Irrespective of the scale you decide upon, the basic principle of a DC system will be the same. In this chapter we are going to look at the polarity of the rails and how they change at points, or crossovers, and how they can come back on themselves if you are not careful. Let’s start with the basic layout, an oval, as this is the simplest and easiest when starting to understand the principles of electrical wiring.

SINGLE RECTANGULAR LAYOUT

The layout will be connected to a speed controller, which will feed positive power to the outer rail and negative (0v) power to the inner rail. The locomotive will now travel clockwise around the track. If the polarity is reversed, so that feed is the inner track and return is the outer track, the locomotive will travel anti-clockwise.

Fig. 1.11 Basic rectangular layout.

Fig. 1.12 Dual rectangular layout.

This is not very interesting as a layout, so we must now introduce some more tracks. From here on we will assume that the normal direction of travel is clockwise, as this will determine how we place our first set of points. We are now going to introduce a second oval outside the existing oval. To do this we must place a set of points in the track to allow the locomotive to move from track 1 to track 2, shown in Fig. 1.12 as ‘P1’ and ‘P2’.

In Fig. 1.12 we have introduced a second oval on the outside of track 1, and this means we need to put at least two sets of points in place: P1 and P2. This allows us to get from track 1 to track 2. You will notice the two orange lines half way between the points: this is where the points will be isolated. When the points are straight through there is no electrical connection between track 1 and track 2, so to run a train on both tracks you would need two speed controllers, or one speed controller connected to both tracks.

POINTS

A set of points – also called a railroad switch or turnout – is used to guide a train from one track to another, such as a spur or siding. Basic points are either left hand or right hand. Other points are high speed points, normally twice as long as the standard point set, and curved points. Non left or right points are also available, and come as double slip or triple slip, giving two or three outlets from the single incoming direction.

Points are also divided into insulated frogs (the frog is insulated from the power) or electrofrogs (the frog is connected to the ‘closure rails’).

We will now look at a set of points to see how it works electrically.

Fig. 1.13 Parts of a points set.

In Fig. 1.13