An electrical disaster (A geek tragedy)

This is how I managed to destroy an Intellibox (IB) and two boosters at once. Well OK, it is still somewhat of a mystery, but here is the story...

I have 4 power districts on my layout, powered by my Intellibox and three boosters.

Everything shares a common ground, including other small devices around the layout that run on 16VAC or 5VDC or 12VDC. I run using mixed Motorola and DCC protocols.

One of those devices is a turntable which takes 16VAC and rectifies that to drive the motor using DC. There are six contacts that go to the turntable:

• Track center rail
• Track running rail #1
• Track running rail #2
• Motor positive
• Motor negative
• Solenoid

The track connections are digital, i.e. a square wave AC signal.

The turntable motor connections are all about 20V DC 

I was trying to resolve a contact problem and I was measuring the voltages on the contacts shown above and I may have measured the voltage between the turntable power contacts and one of the rail contacts. A voltmeter should not be able to conduct much current between its probes.

The next thing I noticed was that the IB screen was dark. It had blown the 3A fuse on its power supply line. I replaced the fuse. The Intellibox complained of a short and then presence of an external voltage. After that it would no longer power on. I attempted a repair of the Intellibox.

After placing another Intellibox (running version 1.55) in service, I found that the sensor bus was reporting nonsense, and the last booster in the chain of boosters was making trains in its section move, and lights flicker. I traced the problem to the first and second Märklin 6015 boosters! Once I removed them, trains in the last power district worked normally and there were no spurious sensor reports.

I obtained a used Märklin 6017 booster and tried that, and I got the same result. No matter which of the three Märklin boosters I connect, I get s88 interference and trains start running even when the IB is in STOP mode. It is as if they are putting analog current out.

I have an old Modellbahn Ott 100W booster and I connected that in the same place as the Märklin boosters and it does not exhibit any problems.

Update 2024-01-05

I obtained another Märklin booster - a 6015.

This one does not send bad output to the tracks, but when rail power is on, I get the junk s88 readings. This is now making me suspect that there is something wrong with the s88 bus of the Intellibox. Track output seems to be leaking into the s88bus, but only in the presence of a Märklin booster. I will be retesting to see if I can locate a defective s88 module, however I believe this is not the case because with the Ott and Power 3 boosters, they all work fine.

Special Option 901 = 3. This controls the asymmetry of the digital signal, and a value of 3 is recommended when using 6015 and 6017 boosters.

Here is a summary of the behavior of each of the 6 boosters I have:

A = Märklin 6015

B = Märklin 6015

C = Power 3

D = Modellbahn Ott 100W booster

E = Märklin 6017

F = Märklin 6015

IB 1.203   IB -> A -> B -> C. Everything was OK

IB 1.55   IB -> A -> B -> C. STOP: flickering and trains moving  GO: s88 garbage

IB 1.55   IB -> A.  STOP: flickering and trains moving  GO: s88 garbage

IB 1.55   IB -> B.  STOP: flickering and trains moving  GO: s88 garbage

IB 1.55   IB -> C.  All OK

IB 1.55   IB -> D.  All OK (See update 2024-01-11)

IB 1.55   IB -> D -> C.   All OK (See update 2024-01-11)

IB 1.55   IB -> E. STOP: flickering and trains moving  GO: s88 garbage

IB 1.55   IB -> F.  STOP: OK  GO: s88 garbage

Update 2024-01-06

Sometimes, when one of the Märklin boosters is connected, I can select a loco address if the track power is off. If the track power is on, then an attempt to select any loco is met with the message "Error" in the loco address area. 

(Note the irony in that the error message has German style hyphenation on an English word! I noticed this error is not in the IB control though.)

I wrote to Uhlenbrock support and described this problem and they replied saying this error occurs if the Loconet is corrupted and that the Intellibox is in need of repair. (See below on an update on this.)

Update 2024-01-11

We have found that if we disconnect the connection (red) to the rails, from a Märklin 6015 booster the corruption of the s88 bus stops, and returns as soon as it is connected again.

My son and I spent a day disconnecting everything from the red feed in one of the power districts (all trains and K83 / k84 modules) and it makes no difference. To me this now suggests that there is electromagnetic interference occurring between the bundles of s88 sensor wires and the track power lines. The s88 bundles are all shielded cables and have never given any problems in 20 years.

We also found that if we waited long enough, the Modellbahn Ott booster does indeed also precipitate false s88 changes, but way fewer than with the working 6015 booster we have.

If we connect the Power 3 Booster to any of the 4 power districts, no corruption of the s88 bus occurs.

I now believe that the IB is not defective in terms of a bad s88 bus port or booster output. I also think the corruption of the Loconet is because the IB gets overwhelmed by the number of s88 changes. This explains why the loconet goes haywire when track power is on, as that is when the false s88 messages come flooding in.

So despite the IB working perfectly with Märklin boosters for decades, a 6015 no longer works with this IB. The only difference I know of is that this IB is running a newer version of the firmware (1.55). If version 1.55 really did not work with Märklin boosters I am sure that this would be a well known problem though.

Uhlenbrock now maintain that the Märklin boosters do not work well with DCC signals. This is strange because they have worked fine in the past and there is a special option (901) which specifically adjusts the symmetry of the digital signal to support them. Uhlenbrock recommend using Power 3, Power 4 or Power 40 boosters instead.

The difference in behavior of my original 6015 boosters (A & B) plus the 6017 (E) I bought on eBay compared to the 6015 (F) I bought on eBay, make me believe that both my original boosters died and the 6017 I bought, also suffered a similar fate before. That booster (E) has now been returned.

I am now looking for Power 3, Power 4 or Power 40 boosters.

I am also going to test with sending only motorola packets to rule out DCC as being the issue, and I am also going to get an old computer going that will allow me to load an older firmware version to see if that resolves the problem.

Update 2024-01-14 

I got rid of all DCC signals by setting the following special options:

SO 6 = 1

SO 12 = 0

SO 22 = 6

SO 25 = 2

SO 901= 1

SO 904 = 28

SO 907 = 1

SO 909 = 198

SO 931 = 1

As expected, the Märklin booster still causes corruption on the s88 bus.

Update 2024-01-28

I managed to downgrade the firmware of the IB to 1.203 - which is what my original IB was running.

It behaves the same. So it is not the firmware version.

I have some second hand Power 3 boosters on their way from Germany. I hope they resolve the problem.

Resolution

After replacing the Märklin boosters with Uhlenbrock Power 3 boosters and adding a fourth booster instead of using the IB output, everything is working again.  The nature of the failure is still a mystery.

Whole train lighting

Seeing an illuminated model passenger train at night is a magical experience. Installing lights makes the trains seem more alive and presents a project within the building and operating of a layout.

There are many, many ways to illuminate passenger coaches. Some methods are more expensive than others, some are easier to install than others and one can find advantages and disadvantages of every approach.

Each approach is a combination of a number of factors:

• Lighting technology: Incandescent/LED
• Battery or track power
• One, or multiple, power pickup shoes for the train
• Full rectification of half wave rectification
• Approach used for anti-flicker
• Permanently coupled rakes or current conducting couplers
• Off-the-shelf solution or DIY
• etc

I have about 40 passenger cars that I wish to illuminate. 

• Unless one is aiming for a classic toy era style, LED lighting is clearly a no-brainer.
• The high costs of current conducting couplers rules them out for me
• Multiple pickup shoes create too much drag on long trains (and they are not cheap either)

I decided to use the following approach for my first train:

1. LED utilizing cheap 12V LED strips.
2. Track power to be used
3. Single power pickup shoe per train
4. Permanently wired conductors run the length of the train
5. Full rectification of digital track  power
6. Capacitor for anti-flicker
7. Inrush current limiting
8. DC-DC converter used to set brightness
9. Twin wires run along the length of the train to each coach

The approach is very economical but of course the biggest problem with a whole train permanently wired together is how to service an entire train, getting it on and off the layout can be tricky. I have solved that problem with a whole train cradle (which will be the subject of another post).

Steps to install whole train lighting

I have now completed an entire train and I report the steps I used to add the lighting.

The circuit I used is described in a lot of detail in the page Modelling with LEDs, particularly in the section on lighting passenger cars.

The train I happened to pick turned out to be rather tricky because the design of the Märklin coaches does not make installation of any type of lighting very easy. The metal weight in the floor of the coaches is used to hold the close coupler guide mechanisms in place, as well as transmit current to the next coupler. The chassis, weight, both couplers, seats and body of the coaches all have to be assembled in a single step and it is rather tricky to get all six components to be properly aligned at the same time, and that is before we start adding wires and lights. Things did get a bit better once I had completed a few though.

The train I selected was made of the more modern models of the Donnerbüchsen such as item 4313, 4314 with goods wagon 4315.

The logical place to start is in the goods wagon as it has space for the rectifier and capacitor. The goods wagon already had some tail lights and a pickup shoe. I used a 2200uF capacitor and added an inrush resistor (1K Ohm), and a 1N4001 diode in parallel to the resistor.

To that I connected a DROK DC-DC converter that powers the strips in the train and the tail lights. I placed it opposite one of the sliding doors such that I can easily access the voltage adjustment screw through the door.  I added an additional resistor to the tail light circuit to reduce their brightness.

Since I was not going to use current conducting couplers, I needed to find where I could pass the wires into each coach. After checking the limits of the coupler mechanism movement, I decided to drill small holes next to the brake pads. For the passenger coaches the holes had to be drilled at a slight angle so that the hole comes up through the end seat.

Once the 4 holes were drilled I opened the coach up and removed all drilling remnants.

Initially I ran the wires out of one coach and ran them parallel to each other into the next like this:

I soon found however that the wires can hang too low so I realised I needed to run them up and over the coupling like this:

I then decided that since I was permanently coupling the train together, I may as well use permanent couplers. Having just recently got a 3D printer working, I designed and printed some couplers and replaced each pair of close couplers with my ones.

(At the time I did not have any black resin so I used clear resin instead.) 

I was using 30 AWG wires that are very flexible but were rather thicker than they need be. Here you can see how the wires have to come up through the end seats.

I glued in some cheap, seated passengers, and simply soldered the wires onto 10cm of strip.The brass weight held the strip while I soldered onto it.

Since both wires are black and I had to keep track of which was positive, I ensured that I always stripped the end of the positive lead. Only once it was soldered to the positive side of the next LED strip did I strip the negative wire.

On the underside of the roof of each coach is a sprue from the manufacturing process which I cut off so that the LED strip could be mounted through the middle of the car.

Since the peel off backing of the LED strips are completely unreliable, I attached the LED strips to the rooves using 3M VHB double sided tape. The columns used for fastening the shell onto the chassis are less than 10cm apart so the LED strips had to be placed diagonally.

Once the whole train was done and placed back on the layout, I was able to set the brightness of the lights using the adjuster on the DC-DC converter.

The capacitor keeps the train illuminated for a couple of seconds after losing power. It is certainly adequate for momentary power interruptions. The DC-DC converter keeps them at a constant brightness. I will also try a train that uses a resistor instead of the DC-DC converter to see if a slow dimming is preferable.

Modelling with LEDs

Modern modeling uses Light Emitting Diodes (LEDs) extensively. This is because they offer numerous advantages over older technology, such as incandescent 💡 light bulbs:

• They are small
• They are cheap
• They are long lasting
• They use very little current
• They do not get hot
• They are available in many colors (including 'warm' and 'cool' white)
  

Unless you are trying to reproduce models as they were in days gone by, you are going to be using LEDs on your models. They are not difficult to use but one does need to learn a few simple rules to use them.

The aim of this page is to explain the theoretical side of what is needed to power LEDs, how to connect them and even how to produce good results in moving model trains. I will be starting off with some very fundamental principles and building up to powering LED strips from digital power. The actual installation of lights inside building is covered here, this is about what has to be installed.

LED packages

LEDs come in a variety of different forms and sizes (called packages in the electronics industry).

Through-hole

Typically round 2mm, 3mm, 4mm or 5mm. Rectangular and other shapes are also available.

3mm & 5mm LEDs

 Surface mount (SMT)

These are even smaller than the through-hole packages and are usually soldered directly to circuit boards by machines. One can now also buy them with tiny wires already attached and these are ideal for model building.

The different sizes are expressed using a 4 digit code that is made up from the length and width of the LED in tenths of a millimeter. For example a 2835 is 2.8 mm by 3.5mm. 5050 is 5mm x 5mm. Note, however, that some LED sizes are expressed in thousandths of an inch instead, so a 0402 SMD LED is is 1mm x 0.5mm. It is so small, it represents an object 87mm x 43mm in HO scale! - smaller than a lightbulb.

An 0402 SMT LED with wires.

  Strips

White LEDs are also commonly found in long, flexible strips up to 5m (16') long. These are made using surface mount LEDs. They are pre wired and ready for use with 12V (sometimes 24V). One can cut them to small lengths, typically 5cm long. These are ideal for passenger car and station lighting. They often use 5050 or 3528 sized LEDs. They are available in various colors, including warm, and cool white.

These strips come with a crummy adhesive backing that will not stick for long, and so should be ignored. They need to be attached with a quality double sided tape such as 3M VHB tape.

Multicolor neopixel etc.

There are components that comprise 3 (R,G, B) or 4 (RGB+W) LEDs which allows the color of individual LEDs in a string to be digitally controlled independently. These fall out of scope of these fundamental concepts.

Electricity fundamentals

In order to understand how to connect LEDs up we do need some very fundamental understanding of electricity. Specifically we need to know a little bit about voltage, current and resistance. It may aid the understanding of these concepts by thinking of electricity rather like water in a pipe. For this analogy:

• Voltage (V) - think of the Voltage as the pressure/speed of the water in the pipe. Measured in Volts
• Current (I) - think of the Amperage as the diameter of the pipe. Measured in Amperes (Amps, A or mA. 1A = 1000mA) 
• Resistance (R) - think of resistance as obstructions to the flow of water in the pipe, such as blockages or mesh grates that slow the water down. Measured in Ohms (Ω)

These three things have a simple relationship between them: V = I x R (Ohm's Law) and this formula is used to calculate things in all circuits, but fear not, most of the calculations have all been done already.

Just like a pipe, where water can travel in both directions, so can electricity flow in either direction along a wire. If the pressure is higher at one end, water will flow to the other end. If the voltage is higher at one end of a wire, electricity will flow to the other end of the wire, so long as it can get out.

Like pipes, larger amounts of current (Amperes) need thicker wires.

Series and parallel

We will talk about connecting things in parallel or series, let's just make certain the difference is clear.

Series connection

LED lighting circuits

The topic of LED lighting is a popular one, perhaps because there are always so many answers!

The big question is always how much resistance is needed to protect the LEDs, but this usually leads to other questions: "How bright do you want the LEDs to be and how much voltage will be used to power them?"

Illuminated street

I describe here the steps I took to mount the BUSCH HO 2878 backdrop on my layout with two sets of lights, the windows and the streetlights. Here is the finished product so one can see the end result that I was aiming for...

Emergency stop

Now that my layout has been built out over a fairly large area, I have decided it would be good to have some emergency stop buttons at strategic points around the layout for those times when one sees an impending disaster and one needs to switch off the track power quickly.

I have had some big industrial buttons similar to the ones I have seen on real German platforms lying about for many years so I decided to wire them up.

S88 panel

I decided to add a length of white LED strip underneath the layout to illuminate the panel where I connect all the track detection wires to the s88 modules. The additional light makes it much better to see when adding a new s88 detection point.

I try to bring the wire bundles in to different point on the panel and leave ports open for when I use the unused wires in a bundle. This is why some of the s88 modules still have some unused sockets.

Viessmann 5210 Signalsteuerbaustein

I use the Viessmann signal modules to drive my light signals from k83 (Viessmann 5211) type modules.

Advantages of these modules are:

• You can use momentary contact decoders (k83) type instead of K84s
• Once a signal aspect is selected, it is latched (held) by the module
• Each module can support two signals (up to a 3 aspect plus a 4 aspect)
• It has the ability to handle the Dunkelschaltung of German distance signals on the same pole when the Hp signal is on aspect 0
• It can use 16 VAC or DC input
• The signal lights fade out prototypically

I find it useful to mount them on Velcro strips as shown below. In this case I needed to drive 3 HP0/1 signals and one Vr0/1/2 signals plus a couple of turnouts so I needed two 5211 modules to do the digital switching.

Connecting a track detection point to an s88 module

The technique of obtaining train location feedback from the train layout is well known and one typically uses a Märklin s88 module or one of the many modules that perform the same or similar service, such as the Viessmann 5217 modules.

Understanding how to connect the length of isolated track to the port on the module is one aspect of the job. Another is the technique of how to actually get the signal from the track all the way around to where the s88 modules are located. This page documents my technique for doing this.

Source of fine wire

One of the coils I have been using has black wire and all the others have the typical copper colored wire. I have thus been using the black wire in areas where the wire may be visible.

Today during tidying operations in the workshop I came across some old power supplies that I had kept for scavenging parts and decided to take the parts I may need and throw the rest out. I cut out bridge rectifiers, big diodes and resistors, etc. (if their wires are long enough to be reused). I tried to break off  a relay and the it broke revealing a nice coil... more nice fine wire. I decided to harvest some more coils and in one I came across the finest wire I have ever seen... it came out of a 24V DC Omron relay and the part number enabled me to find the data sheet - and the coil information on the data sheet says the wire is rated for 21.8 mA! This will be ideal for LED circuits. The wire feels like human hair...

I tried to take pictures of the wire alongside the Märklin motor coil wire....  The big black wire is the Märklin coil wire, the copper wire the wire from the Omron relay.

Water crane lamp signal Ve7

Water cranes, used to supply water to steam locomotives, had a signal lantern mounted on the arm that could swing over the track.

These lanterns had red on the sides and white on the front and back. This means that if the arm was over the track, a red signal would be presented to any locomotive on the track in either direction, warning the driver that the arm was over the track. When swung away off the track, white lights would be presented. The official signal designation is Ve7

I explored the possibility of creating illuminated replacement lamps for the water cranes I am building.

I used transparent styrene to create a lantern the same size as the original solid plastic items supplied with the Faller 120137 kit. Into that I inserted a surface mount LED. In order to keep the brightness very low I used a 47K Ohm resistor at 12V - resulting in a current of only 0.2mA!

Here is the first lamp with the Faller original lying below it. It is supported only by the two wires going to it.

Arc-welder in HO

I designed and made a welding machine out of thin card

Tunnel signal

I decided to place some signals inside the underground S-Bahn tunnel so that they can be seen from the station, but did not want to spend the money buying a ready made signal that would not be seen much. I only expect to see the signal light within the blackness of the dark tunnel. I decided to use some small LEDs and drive them with a stationary decoder. (An old loco decoder).

Stationary decoder

In order to switch some light circuits utilizing an old loco decoder I took an old Märklin 6080 decoder and mounted it on a small board that can be plugged into the digital signal and have two independent light circuits plugged into it.

Voltage visualization

I was connecting a Semaphore signal and I decided to try powering the light using the 5.1V DC supply and since it is an LED light I needed to get the polarity correct. My other color light signals also have LEDs and they all have their black lead with the diode connected to the common ground since the Viessmann signal modules produce a negative voltage relative to the common ground. My 5.15V DC supply is however positive relative to ground so the semaphore signal needed to have its yellow wire connected to ground and the brown lead with the diode connected to the positive power supply.

I realized that I needed to keep track of the various voltages I have available on my layout so I created this visualization.

Changing wire color

When I started building my layout I bought three roles of household 12 AWG wire in the three main colors that I would be using.. Red for digital, brown for ground and yellow for 16V AC

Now that I also want to run a 12V DC line I need a fourth color but I balked at the price of a whole role of heavy gauge spool of wire. I bought a shorter length of smaller gauge wire but when I came to install it, I decided that I really did need to use a heavy gauge wire - low voltage means supply can quickly run up to a high amperage current if there is a short somewhere so I don't want my supply bus to go up in smoke.

Then I had what turns out to be a really simple idea... instead of buying more wire, I decided to simply color a good length of wire using permanent markers. A light colored wire is easy to change to a new color so I took a length of yellow and made it green by running a fat permanent marker along its length a few times.

If I were starting from scratch I would buy a single good sized roll of heavy gauge wire - say white - and simply color it red, brown, black, red, blue yellow as needed.

Here is my new role of green wire and the original yellow.

DC power supply

Last march I talked about running a DC power bus around the layout in addition to the 16VAC and digital lines. An obvious source of clean DC power is an old PC power supply harvested from an old computer.

I found that other hobbyists (Example 1 and 2) are doing similar things with PC power supplies so this weekend I went ahead and built myself an interface between any PC power supply and my DC power bus.

Laying K-track

I have just a little bit of track left to wire up so I decided I had better document how I do it before I have nothing left to photograph...

Martinez type contact

On my old layout, I needed to add some sensors in a hidden area that was very unaccessible.

This is how I planned on adding an s88 contact point as needed in hidden areas of the layout. The advantage was that I could simply glue the assembly down next to the track without having to lift track, cut rails and relay the track.

A big disadvantage was that track cleaning devices were likely to destroy the switch or get hung up on them.

Antonio Martinez has a much simpler technique using aluminium foil.  I am abandoning my experiment and have started my first Martinez type contact. I stuck a length of packaging tape on one side of some foil (thus insulating one side), then cut it out with a tail of bare foil that I twisted and fastened into a Märklin socket for easy connection to the s88 lead. Here it is, insulated side up.

I can them simply pin it down over one side of the rail so that it cannot touch the center studs and covers one running rail. If it wears out I can easily make another to replace it.

Update: These tin foil switches worked without any problems for over 9 years. Even then, they did not fail, they were taken out of service as I dismantled the layout.

Wiring track feeds to bus wires

A sample of the wiring seen from below. Multiple leads come down from the track and are connected to the large bus wires with run and tap splices