DCC and the “Can be done in DC” discussion.

A lot has been said about the usefulness of DCC now that a loco equipped with a sound chip from QSI and runs on DC is available. While this offers sound that will surely bring a new dimension to DC operated layouts, sound is one of the many features that is available on a DCC layout.

Operating a QSI equipped loco on DC will require the operator to slightly change the way he uses the throttle compared to a normal DC loco. The first 30 – 40% of knob movement is used to provide 5 – 7 volts to the track and hence the loco to power the QSI chip. The loco will not move for this first part of throttle movement. Most normal DC locos will be moving by the time 5 – 7 volts is at the track. Moving the throttle knob further now will cause the loco to move off and now the motor is under the command of the chip that will move the loco according to throttle (knob) position. The loco will stop when this 30 – 40% position is reached when slowing down. If left at this position the sound chip will produce idling sounds. Moving the throttle to zero, stops the sounds altogether. The horn/whistle and bell, if applicable, can be sounded while the loco is moving by operating the direction switch on the DC throttle. This will not change the loco’s operating direction.

While the sound of the QSI equipped loco is very impressive on a DC layout, it has to be operated, apart from the above slight throttle difference, the same as any DC loco with all the normal block control operation. The QSI chip does not bring the “DCC things” that I and others talk about to the DC layout. Fitting a QSI chip to one of your existing locos would add sound to the loco and would allow it to work on DC. QSI sound chips are only available as OEM fitted components to certain loco manufacture’s locos. These QSI chips are not available to modellers yet as an after market item. Other sound manufacturers like ESU and Soundtraxx have not made sound decoders that work as well on DC as they work on DCC like the QSI chips.

The major advantage of DCC over DC is the total independent control of each loco without block control and use of control panels. This allows DCC users to operate their locos instead of operating their layouts (control panels). Running a train on a DC layout requires the continual switching of blocks to enable control of a loco when there are a few operating trains running at one time. In DCC there are no operating limitations to where the loco can move to as there is in DC, to the “edge” of the block. The locos can operate to any point and can even move from one side of a yard across many parallel mainline tracks to the other side by just operating the points and the throttle.

As can be seen the DC chip or DC decoder just allows for sound and no independent control. Some modellers talk of some sort of throttle that will provide all the sounds and independent control that a DCC decoder provides, in DC. This could be done with some sort of computer/software and DC decoder like the QSI in the loco. The QSI Quantum Engineer will allow all the sounds to be accessed and controls the loco but the loco is still under normal DC block control. Another arrangement could be built by a “user” that would require manufacturing a circuit board, fitting this board into a loco, using a computer with a “user” developed software that would make some sort of “digital command” that could be sent to each loco down the track. This could provide independent control in DC.

The cost and the “user” required electronic/computer skills would just about rule out most DC modellers. Sure signals could be used and some sort of computer controlled block switching could provide some form of independent control. Adding PWM circuits and circuits to control lights with different effects will require a PIC microcontroller. This DC decoder would have to be fitted into the loco. The larger the circuit board the harder it is to fit in the loco. I would not be able to put a cost on this or even have the computer/electronic skills to do it and I am an electrician with hobby electronics experience for close on 40 years. The fact that “one or two” modellers that have these skills and say that all these “DCC things” can be done in DC does not mean that it is “available” to all DC user.

This is a gross overstatement and does not warrant the time to even contemplate the possibility that modellers can have it.

One very clever electrically minded modeller with computer skills has said this is all possible and has “fuelled” a debate between myself and him that might have you all asking why go to DCC when he says that all that I say about DCC can be done in DC. He says that you can use a DC decoder and some cheap DC computer command system. What he has forgotten to mention is that model train control system manufactures of the past have already tried all of this and found too many limitations. Some of these companies no longer make control systems.

Irrespective of whether this can be done and the cost is a useless debate as there is already in place a very cheap system that will provide all these above features and more, at a cost of about A$200 including the “DC loco chip” into 5 locos that this modeller talks about. Manufacturers have spent thousands of dollars to develop what this modeller is trying to advocate.

Enter entry level Digital Command Control, commonly called DCC. So what this modeller is trying to achieve with DC is what has already been done and by a similar method that he is advocating, using a DC decoder and a computer. He wants to re-invent the wheel. He cannot get used to the term “DCC” so good luck to him.

The “DC chip” is the DCC decoder in the loco. The “DC computer” is the DCC system comprised of a command station (brains – computer) and the booster (power supplying unit) and the throttle is the “specialised DC cab”. So as this modeller has so “rightly” stated these things can be done in DC. The technology is called DCC. Miniaturisation in electronics using surface mount technologies has enabled sound and motor control on a circuit board that is small enough to fit into an N scale loco.

Fitting a motor control only DCC decoder into a HO loco is relative easy and getting easier with the newer smaller decoders. Prices of these DCC decoders start from A$20. DCC system prices start from A$100 for a basic entry level to $700 for more advanced systems with more features. To run and program locos, all that is required is the entry level system.

As with most facets of our hobby we aim or require higher standards. Modern manufacturing processes have produced a more detailed locomotive. Can motors with small gearboxes have improved the running qualities of our locos. The modeller soon sees which models look and run better and choses those to run and relegates the others to static displays or ones that are rarely used and stationed in the roundhouse or yard.

The same can be said for control systems that we use to run our trains. DC was a replacement for clock work mechanisms and now DCC will replace DC and some other operating system will replace DCC in the future. Technology will make sure of this and the fact that modellers want better models will ensure this. I am looking forward to locos that only need power at certain places on the track to charge up onboard batteries and operate with radio control thus removing all the electrical hassles including power pickup across points that we have now. All this will be in HO locos. Anyway this is in my dreams. DC will be replaced at a rate determined by owners and what is available. Modellers who don’t want to have the benefits of DCC will be many and will still enjoy operating their layouts and I will enjoy seeing them, but if they are layouts that are based on operation more than straight out running, then they will be difficult to operate.

I only use DCC because I want more out of my train operation and yes it does cost more and takes more time, but it is worth it for me and many others.

If you have noticed at exhibitions, the trend is layouts of the walk around type. These were not seen 10 – 15 years ago. More home layouts are becoming “walk around” and/or switching point to point layouts and less of the traditional continuous running types. So even the type of layouts have changed and so will our models and operating systems How many modellers are operating locos that are older than 15 to 20 years old. How many modellers are still operating their first layout if they have been modelling for more than 10 or so years? So you see changes are always happening. Some people want to move with the changes and some don’t. There can be many reasons.

Remember it is a hobby and if we are not having fun, then it is time to do something else and give trains away.

DCC Features:

Total independent control of any loco.

This is the major feature of DCC that allows unlimited operation more like the prototype. This allows operators when running trains, to control locos in DCC instead of operating the layout as what is normally done in DC. This leads to a much more rewarding operating experience. Other features are:

Layout wiring is much easier - no complicated control panels with blocks.

Fine low speed control due to PWM motor control techniques including back EMF in some decoders.

Tailor speed motor speed curves (voltage) to give optimum operation using start, mid and max and/or speed tables.

Using the above speed curves will allow all mechanism to operate similar irrespective to type and gearing.

Double/triple heading locos with different mechanism is now much easier.

Lighting effects including headlights, marker, mars, beacon, strobe lights etc can be set up.

Lights can be selected on, dim or off and are on with the loco stationary and can be directional.

Other accessories like smoke generators can be selected on and off and make smoke when the loco goes slow.

Some system will allow route control selection from the throttle.

Systems allow for multiple throttles.

Walk around throttles. Some systems have infra red or radio control throttles.

The basic 3 amp booster will allow for about 10 locos including sound locos to be operated.

The more expensive systems have more features.

Decoders and system are getting cheaper, so going to DCC will not be as expensive.

As can be seen a QSI chipped loco on DC will provide sound that certainly does add the extra realism but will not provide any of the above features that are standard in all DCC systems. The ease and the ability to do most of the above will depend on what system you have decided on. The more expensive systems will provide more features. All DCC system will provide basic independent control and will allow decoders to be programmed to adjust the Configuration Variables CVs for short, to fine tune operation and control.

The benefits of DCC will be different for all operators and will depend on the way a layout is run. Obviously a single operator layout will not benefit as much as a multi operator layout does due to the fact that independent operation is not as much of an issue. Benefits will also vary with the type of DCC system used.

A couple of the most important features I find, this is not what I recommend for everyone because each layout is different. For me they are:

4 digit addressing.

Programming on the Main (P.O.M.).

Walk around capability with a cab bus and radio control.

Throttle types and available options.

One of the most important deciding features when buying a DCC system is how you find a throttle feels and how easy you find operating it personally.

A little background to DCC:

Introduction: The booster of a DCC system supplies approximately 14 volts square wave 8,000 Hz A.C. to the track all the time. With normal DCC wiring with the entire track powered at all times. This 14 volts is supplied to each loco on the track. The bridge rectifier of the DCC decoder mounted in each loco produces approximately 13.5 volts DC that is provided to the PWM motor driver and to PWM function outputs to control individual lights etc on the loco.

To operate each loco individually while all locos are powered, each loco mounted decoder has a unique address. These can be either a 2 digit or 4 digit address and what type of address is used is determined by the DCC system used. The beauty of using the more expensive 4 digit address is that typical loco 4 digit road numbers can be used, eg 3801 etc.

Connecting the DCC system: To convert an existing layout wired for DC operation, all that has to be done is to connect the DCC system booster to one of the cab controllers and select all tracks to the same cab and now DCC power will be supplied to the track. Connect the booster with a 12 volt 21 watt lamp in SERIES with one track feeder will protect inadequate wiring that may be evident on existing layouts. This will prevent the booster from supplying more than about 1.7 amps and will prevent the booster from ever tripping when there is a short. See later for more details.