“Hey! Who’s controlling my train?!” This plaintive cry was heard once too often during a recent operating session on my layout, sparking the decision to convert my layout from cab control to Digital Command Control (DCC). The layout was controlled by a conventional cab control system, using rotary switches in multiple control panels to allow operators to control their trains. This system worked fine, providing that one operator did not cross into a block controlled by another operator. At that point, the first operator would lose control of the train, or worse, cause a short-circuit between the two cabs. One of the major attractions of DCC is the elimination of blocks, allowing more direct control of your train throughout the layout, and elimination of the block boundary problem.
The Original Configuration
The layout was controlled by five PFM-style sound systems: two PFM Sound System IIs; one SoundTraxx infrared steam sound system; one custom-made steam sound system made by my friend Gordon North; and an internal combustion sound system, also made by Gordon. Clearly, sound is a critically important dimension to me, and conversion to DCC would have to include high-quality on-board sound. The introduction of high-quality sound decoders, such as the SoundTraxx Tsunami and the Loksound series of decoders, has made conversion of a layout, even in HOn3, a practical and enjoyable venture.
Reasons to Convert to DCC
There were several reasons I believed that conversion of my layout to DCC would be beneficial. First, I would be able to eliminate the blocks required by the current cab control system. This would allow direct control of the operator’s train at all locations on the layout. Second, I would be able to control the sounds from the hand-held throttle, including blowing the whistle. This was something not possible with the PFM Sound System IIs. Third, this is the direction in which the technology is moving, as shown by the number of locomotives being introduced with pre-installed sound decoders, such as Blackstone Models recently introduced K27.. Finally, I would be able to eliminate a pesky phantom short circuit that only appeared during operating sessions, particularly when guest operators were present! I also believed that operation would be enhanced since the operator would be focused on the action at railside, rather than being concerned about controlling the electrical blocks.
The purpose of this article is to present answers to questions that arose as I worked through the process of converting my layout to DCC. I hope this information will be useful to you should you decide to embark on a similar project to greatly enhance the operation of your layout, whether you operate by yourself, or with many friends.
Important Questions That I Asked
- Which system would best suit my needs?
- Do I need to completely re-wire my layout, or can I utilize the existing wiring?
- How do I handle reversing sections, such as a return loop or wye?
- Will my turntable require special consideration?
- Will I be able to fit sound and motor decoders into my HOn3 locomotives?
- What, if any, improvements could I make?
- Can I control turnouts and other accessories using DCC?
- Will I be able to double-head locomotives, and use helper service?
- Where should I begin such a project?
- How long would this conversion take?
Decisions, decisions
Once I made the decision to convert my HOn3 D&RGW layout to Digital Command Control, I faced a difficult decision: which DCC system to purchase? To help me make this decision, I developed a list of characteristics which the system I purchased would have. The most important requirement was that the system was simple and clear to operate. This translates to determining which throttle (the handheld unit used to control the trains) I was most comfortable using. Reliability and ready availability were important to me as well. I thought that the ability to throw turnouts remotely would be valuable, so I needed a system that could accommodate a variety of accessory decoders. I was intrigued by cordless operation, so I added radio or infrared control to my list of requirements for future expansion. Surprisingly, cost was not a major factor in my decision. After all, the initial cost of the system would be a one-time event, but I would be using the system for many years to come.
I narrowed my choice of systems down based upon the features that I wanted, and evaluated four systems: the Digitrax Super Chief; the Lenz Set-100; the North Coast Engineering (NCE) Power Pro; and the Model Rectifier Corporation (MRC) Prodigy Advanced. One thing became quickly apparent – all of the systems were of good quality, and would be a good choice. However, I chose the NCE Power Pro system because the handheld throttle best met my needs, was intuitive to use, and was comfortable in my hand. It also had the capability for wireless operation, and had direct control of up to 12 functions, which is important for operation of sound decoders.
 |
Photo 1. The ProCab throttle, included with the NCE PowerPro system, as used on the HOn3 Denver and Rio Grande Western. The PowerCab is plugged into one of the seven UTP panels mounted in the layout fascia. The PowerCab is held in a New Rail Models Universal Throttle Pocket mounted on the fascia of the author’s model railroad.
|
 |
Photo 2. The ProCab-R radio throttle, also held in a New Rail Models Universal Throttle Pocket mounted on the fascia at
|
 |
Photo 3. The radio base station installed on the author’s
|
The layout conversion
Since my layout was originally designed to use PFM-compatible sound systems for operation, I knew that I would need to convert the layout and each locomotive to DCC. While this may seem to be a chicken-and-egg dilemma, I decided that the conversion could be broken down into two phases:
- Conversion of the layout wiring
- Conversion of the locomotives.
I decided to test the locomotive conversion first. This enabled me to develop decoder installation skills and I could test the installation on a test track prior to embarking on the full-scale layout conversion. Additionally, I would need a DCC-equipped locomotive to test the layout conversion. Therefore, my plan was to convert one locomotive to DCC, convert the layout, and finish the project by converting the remaining locomotives.
I began with a simple locomotive conversion – installing a sound decoder into my HOn3 Con-Cor Galloping Goose. I installed a Soundtraxx DSD90LC Goose decoder into the Goose, and tested the installation on a simple test track. Once the conversion was confirmed to be successful, I began the layout conversion.
 |
| Photo 4. The DCC Specialties PSX4 Circuit Breaker mounted under the layout. Power from the NCE Command Station enters on the right, and is split into four circuits. A pair of LEDs is associated with each circuit, to indicate that power is being applied to its power district, and to indicate if a short circuit has occurred. Note that all connections are made using screw terminals. The fourth circuit, at the top of the photo, as reserved for a future power district dedicated to the switch machines |
Note that heavier track power buses are required with DCC since they must be able to handle the entire current load of the layout. This is in contrast to cab control wiring, where each bus carries the current for a limited number of locomotives. The existing common-rail wiring was eliminated when the track feeders were soldered to the new track buses, isolating each of the power districts.
One recent improvement in the electronics associated with DCC is the introduction of circuit breakers designed to handle the higher current draw of sound-equipped locomotives. The original circuit breaker installed on the layout during conversion to DCC was unable to reset itself following a short-circuit. I upgraded the circuit breaker on the layout to a new-generation circuit breaker, the DCC Specialities PSX-4, which is capable of distinguishing between high inrush currents resulting from sound-decoder equipped locomotives and a short circuit. This decoder is capable to resetting itself following a short circuit, even with multiple sound-equipped locomotives in its power district.
The wiring was tested by placing a quarter across the rails with power applied. The wiring is of sufficient gauge if the circuit breaker is tripped. The quarter-test was performed on all track sections. This ensures that a short circuit will be detected on all portions of the layout, preventing equipment damage or even a fire! Once the track buses were completely wired, the block controls on the existing control panels were no longer necessary. However, the control panels were not removed yet, since the turnout controls were still required.
Reversing sections were identified, and power was routed to them through a DCC Specialties OG-AR automatic reverser (Photo 5).
I chose this reversing unit because it is 100% solid state, and responds instantly. In fact, when I first installed the unit it performed so quickly and transparently that I thought it was not functioning! My layout contained three reversing sections: 1. the wye at Pandora; 2. the return loop in Durango Durango
 |
| Photo 5. The DCC Specialties OG-AR Automatic Reverse unit mounted underneath the layout. The input is connected to the appropriate power district, while the output is connected to the track reversing section. Connections are made using screw terminals here, as well. |
The turnout conversion
Once the track wiring was completed and operating to my satisfaction, I tackled conversion of my turnouts to DCC control. The layout currently has 36 turnouts, all of which are controlled by switch machines. I have standardized on the Tortoise switch machine, but a couple of Switchmaster machines are used in areas where I was unable to mount a Tortoise. I initially decided to use Lenz LS-150 accessory decoders for turnout control.
 |
| Photo 6. One of four Lenz LS-150 accessory decoders mounted under the layout. Each LS-150 can control up to six turnouts, or other accessories. Note the diodes used to provide directional power to the Tortoise switch machines. The diodes are connected to the + and – terminals. They are then connected to one terminal on the Tortoise, while the C terminal is connected to the other terminal of the Tortoise. The Tortoises receive their power from the AC connection. |
My decision was based on several factors: 1. each decoder could control up to 6 turnouts, lowering the cost per turnout; 2. the decoders obtained DCC control signals from the track buses, but power to the turnouts was supplied from an auxiliary 12 volt AC power supply; and 3. the decoder could accept non-sequential addresses.
I began by installing a 12 volt AC power bus throughout the layout. I installed the Lenz decoders in locations convenient to the 6 turnouts to be controlled, and connected each Tortoise to a decoder output. Because the Tortoise requires DC current to determine the direction of throw, and the decoder uses AC current, I connected the Tortoises using diodes to provide directional power (Photo 6).
Recently, I installed NCE’s new Switch8 accessory decoder, which controls eight slow-motion switch machines. This decoder obtains its power for the switch machines from the power bus, and therefore does not require an additional power supply. It also maintains power to the turnout at all times.
I began by installing a 12 volt AC power bus throughout the layout. I installed the Lenz decoders in locations convenient to the 6 turnouts to be controlled, and connected each Tortoise to a decoder output. Because the Tortoise requires DC current to determine the direction of throw, and the decoder uses AC current, I connected the Tortoises using diodes to provide directional power (Photo 6).
Recently, I installed NCE’s new Switch8 accessory decoder, which controls eight slow-motion switch machines. This decoder obtains its power for the switch machines from the power bus, and therefore does not require an additional power supply. It also maintains power to the turnout at all times.
 |
Photo 7. The North Coast Engineering Switch 8 accessory decoder mounted under the layout. Note that no AC power connection is required because the Tortoise switch machines receive their power from the track bus. The Tortoises are continuously powered.
|
Once the turnouts were connected, I programmed the decoder with the turnout addresses. After all turnouts within a control panel were converted to DCC control, the control panel was removed. Eventually, all control panels were removed, the trains and turnouts could be controlled from any location on the layout, and the fascia has a cleaner look.
Converting the locomotives
Motive power on my layout consists primarily of brass locomotives which have PFM sound components installed. Conversion of the locomotives to DCC consists of removing the PFM-specific components, and installing the appropriate decoder, or decoders. I removed the RF trap and blocking capacitors installed in the PFM speaker circuit, but was able to re-use the speaker when I installed the sound decoder. Be certain that the impedance of the speaker matches that required by the decoder to prevent damage to the decoder. I was also able to re-use the sound cam for installations using SoundTraxx sound decoders (the ESU LokSound decoder requires a sound cam without a ground to the locomotive frame). Headlight installations required more thought, because the headlight, if installed, was a 1.5 volt bulb powered through a bridge rectifier installed in the motor circuit. The headlight function output from the decoder is approximately 12 volts; therefore, either the headlight bulb must be replaced with a 12 volt bulb, or the voltage to the headlight must be reduced. I had difficulty finding 12 volt bulbs small enough to work with my HOn3 locomotive headlights, so I used a resistor in series with the existing 1.5 volt bulb to drop the voltage to less than 1.5 volts. The value of the resistor is dependent upon the current draw of the bulb, and the amount of voltage to be reduced; therefore, a blanket recommendation of resistance is not possible. The value of the resistor can be calculated by the following formula:
Resistor Value = Voltage to be reduced
Bulb Current (Amps)
Therefore, a 1.5 volt bulb which draws 15 milliamps (0.015 Amps) will require an 800 Ohm resister, assuming that the voltage to be reduced is 12 volts. A 40 ma bulb will require a 300 Ohm resister. Be sure to measure the actual voltage the decoder supplies, typically between the blue and white leads. Light-emitting diodes (LEDs) can also be used for headlights, and other lighting effects, significantly lowering the current draw on the decoder. All decoders must be installed following the manufacturers recommendations to ensure a successful installation. We do not want to let the factory-installed smoke out of the decoder!
Lessons Learned
Conversion of the layout to Digital Command Control has been a project that has greatly increased enjoyment of my layout. Conversion to DCC required about 6 months of enjoyable part-time activity, and resulted in improved reliability of the wiring. Operation was greatly enhanced, and I particularly enjoy simulating helper service with a pair of sound-equipped C-16s. I found that I was able to install sound and motor decoders into my HOn3 locomotives; although the C-class locomotives can be a challenge, it can be done. The recently introduced Blackstone Models HOn3 K-27 locomotive, with its included Tsunami decoder, have added a whole new dimension to operating my HOn3 layout.
I found that re-wiring the layout was a good idea, because I was able to eliminate trouble spots that existed with cab control. The problems associated with reversing sections in conventional DC wiring are effectively eliminated through DCC automatic reversing units. Operators do not have to concern themselves with track polarity – they simply tell the locomotive to move in a forward or reverse direction. Turntable operation was simplified by connecting the turntable bridge rails to an automatic reverser.
One bonus that did not occur to me until after I had made the decision to convert to DCC was that now I would be able to independently control the blade speed and whistle of my Overland Models Rotary OY, adding to prototypical work train movements. I also found that installation of a function-only decoder will allow control of marker lamps and the drumhead on the end of my San Juan
I was very pleased with my decision to eliminate the control panels. While this may seem to be a somewhat radical departure from conventional wisdom, the freedom of operation afforded by elimination of the control panels made this a wise choice. Now, I can throw turnouts from any location around the layout. In fact, a friend has decided to eliminate the control panels on his DCC-equipped layout after seeing how well it worked on mine.
 |
| Photo 8. DCC allows for prototypical helper service. The locomotive can be cut into the train at any location. The two locomotives can then be consisted and run as one, or can be run separately, even by two operators. |
 |
| Photo 9. At the summit, the helper locomotive has been cut off, leaving Mudhen 455 as road power for the rest of the journey. |
 |
Photo 10. Helper locomotive Mudhen 454 runs light ahead of the train she has just assisted up the hill. Prototypical operations, such as helper service, are easily achieved through DCC.
|
 |
Photo 11. DCC allows each train to be controlled independently, without the need for blocks. Care must be taken to prevent a ‘cornfield meet’, especially on blind curves!
|
Recommendations
- Pick a DCC system based upon the design of the hand-held throttle. This is the portion of the system that you will be using the most, and you should be very comfortable with it.
- Be aware of the number of functions the system can support. If you want to use sound decoders, you will need more functions than if you don’t want sound. I recommend at least 12 functions.
- When evaluating DCC systems, determine your requirements in advance. For example, do you want sound? Do you want to control accessories? Do you want radio control? If so, look for ease in control of these features. Also, determine if you can upgrade to the desired features at a later date. I just recently added radio control to my NCE system, and it was as easy as plugging it in.
Bill of Materials as used on the HOn3 D&RGW
- NCE PowerPro with 5-amp power supply
- NCE PowerCab, 2 ea.
- NCE PowerCab-r, 1 ea.
- DCC Specialties PSX4 Circuit Breaker, 1 ea.
- DCC Specialties OG-AR Reversers, 2 ea.
- Lenz LS150 accessory decoders, 5 ea.
- NCE Switch8 accessory decoder
- NCE Decoder Tester
- Locomotive decoders
- SoundTraxx Tsunami TSU1000 and TSU750 decoders
- SoundTraxx DSX sound decoders
- SoundTraxx DSD90LC and DSD100LC decoders for sound and motor control
- Digitrax DH123 and DZ123 motor decoders
- TCS MC1 motor decoders
- TCS FL-1 function-only decoders
- 14 gauge stranded wire, black
- 14 gauge stranded wire, red
References
Strang, Lionel. 2003. DCC Made Easy. Kalmbach Publishing Co., Waukesha , WI
Palmer, John. 1999. The Digitrax Big Book of DCC. Digitrax, Inc. Norcross , GA.
