Update 18 Jun 2010 Added the NCE Z14SR decoder to the lineup. Updated review of Silver Mini to reflect addition of RailCom. Added a few comments about reliability.
Update 23 Apr 2010 I’ve had a very good conversation with TCS tech support about the Z2: They are recommending against using the Z2 for N-scale installations; It is simply too delicate. A shame, because this is a good, and small! decoder. Accordingly, I have removed it from the list.
Most Japanese trains are Multiple Unit (MU) trains—trains with no distinct locomotive, but whose motive power is distributed throughout the train. Typically models of MUs place the electric motor in one of the center-most cars, rather than at one end or the other of the train.
JR East E259 Narita Express
This means that a model of an MU needs at least three DCC decoders for a full conversion: One decoder to control the headlights and taillights in the cab car at one end, another decoder to do the same in the cab car at the other end, and one decoder to control the motorized car in the middle. This situation is unique compared to locomotive-driven trains, which require only one decoder to handle all of these functions, because the functions are all localized in one vehicle.
In this article, I explore the options available to the Japanese rail modeler for using DCC to control the movement of the train via the motor car.
The Perfect Motor Car Decoder
The perfect motor car decoder would have the following properties:
- Cheap—With three decoders per train, equipping a train for DCC can get expensive quickly.
- Small—Motor cars usually have very detailed interiors with interior lighting. A large decoder would spoil that view. Since most decoders have nearly all the features any modeler could want (with the exception of some particularly fancy features), size is often the single most important factor in selecting a motor car decoder.
- 0-function—There are no functions for this decoder to control. Additional functions are (usually) unnecessary, and only take up space and cost.
- Smooth Movement—Momentum and BEMF control are essential for smooth and realistic operation of Japanese trains—especially since many Japanese models are not equipped with flywheels. These features are nearly universal in current-generation decoders.
The perfect motor car decoder might have one or more of the following properties, depending on the model and desires of the modeler:
- One or more functions—In addition to controlling the motor, some like to control the car’s interior lighting via DCC as well. Also, although it is rare, sometimes the motor is in a cab car, in which case at least two functions will be necessary to control the headlights and markerlights.
- Fancy Momentum—Some modelers prefer to have more fine-grained control over momentum features, such as a tunable momentum curve, or a programmable constant-stop distance (very handy for accurate automated station stops).
- Bidirectional support—Some users seek to automate their layouts, to some degree, and such automation often requires (or is at least enhanced by) bidirectional communications, either Digitrax’s proprietary Transponding, or NMRA RailCom.
Actual Decoders: Summary Table
Many decoders currently on the market meet these criteria, which is great news. None of the decoders reviewed below are clunkers—any would be a good choice for installation into a motor car, although for a given model or preference, some will be better than others. Thus, the recommendations merely pick out what I take to be the best of the best—generally those that offer small size at a reasonable price. I have deliberately left out of this review decoders whose size precludes a satisfactory motor-car installation, including some N-scale decoders such as the Digitrax DN143.
What follows is a table of what is currently available. Click on or hover over any element in the table for a description of that element.
| DE22×2 | DE25×0 | Z14SR | M1 | Gold Mini | MX620 | LokPilot micro v3.0 DCC | 73400 | Silver Mini | DCX75D | DCX74zD | DZ125 | EM13 | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Manufacturer | NGDCC | NGDCC | NCE | TCS | Lenz | Zimo | ESU | Uhlenbrock | Lenz | CT Elektronik | CT Elektronik | Digitrax | Kato |
| Rating | ★☆☆☆ | ★☆☆☆ | ★★☆☆ | ★★☆☆ | ★★★☆ | ★★★☆ | ★★★☆ | ★★★☆ | ★★★☆ | ★★★☆ | ★★★☆ | ★★★☆ | ★★★★ ★★★☆ |
| Price | $32 | $23 | $35 | $32 | $60 | $60 | $55 | $46 | $45 | $43 | $33 | $25 | $22 |
| Price per Star | $32 | $23 | $18 | $16 | $20 | $20 | $18.33 | $15.33 | $15 | $14.33 | $11 | $8.33 | $5.50 |
| Recommended? | ✓ | ✓ | ✓ | ✓ | |||||||||
| Height | 1.9mm | 2.4mm | 3.3mm | 3.43mm | 2.8mm | 2.5mm | 3.5mm | 2.4mm | 2.8mm | 1.4mm | 2.6mm | 2.86mm | ? |
| Width | 9.3mm | 11.6mm | 8.6mm | 9.12mm | 9mm | 9mm | 9mm | 7.5mm | 9mm | 7.2mm | 7mm | 8.7mm | ? |
| Length | 29.3mm | 24.4mm | 14.5mm | 14.4mm | 11mm | 14mm | 13.5mm | 10.8mm | 11mm | 11mm | 9mm | 10.6mm | ? |
| Total Area | 272.49mm² | 283.04mm² | 124.7mm² | 131.328mm² | 99mm² | 126.0mm² | 121.5mm² | 81mm² | 99mm² | 79.2mm² | 63mm² | 92.22mm² | ? |
| Functions | 2 | 0 | 4 | 2 | 2 | 2 | 2 | 2 | 2 | 2 | 4 | 2 | 0 |
| BEMF? | ◯ | ◯ | ✕ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ | ◯ |
| Fancy Momentum? | ✕ | ✕ | ✕ | ◯ | ◯ | ◯ | ◯ | ✕ | ◯ | ✕ | ✕ | ✕ | ✕ |
| Transponding? | ✕ | ✕ | ✕ | ✕ | ✕ | ✕ | ✕ | ✕ | ✕ | ✕ | ✕ | ◯ | ◯ |
| RailCom? | ✕ | ✕ | ✕ | ✕ | ◯ | ◯ | ◯ | ✕ | ◯ | ✕ | ✕ | ✕ | ✕ |
| Max Current (cont. total) | 500mA | 1000mA | 1300mA | 1300mA | 500mA | 800mA | 750mA | 600mA | 500mA | 1000mA | 1000mA | 1000mA | 1000mA |
| Max Current (peak total) | 2000mA | 3000mA | 2000mA | 2000mA | 800mA | 2000mA | 800mA | 2000mA | 2000mA | 1250mA | 1500mA |
Reviews
NGDCC DE22x2 & DE25x0
NGDCC specializes largely in drop-in decoders, with only a handful of mature hard-wired products. The DE22x2 and DE25x0 decoders, which differ only in the number of functions they provide, are listed as prototypes, although it is possible to purchase them. Although both provide a suitable number of features, the large size of these decoders cost their ratings considerably. Interestingly, one bonus is that they can handle a comparatively large stall current: these are most suitable for very high-draw motors. These decoders are not available outside of Japan.
Summary: Too large to easily hide in the shell of a motor car leaves these decoders as merely adequate. There are better choices elsewhere on the market.
Links: NGDCC website, DE25x0 page,DE25x0 manual; DE22x2 page, DE22x2 manual.
NCE Z14SR
NCE specializes in medium- and large-scale decoders, but the Z14SR is their recent entry into the N-scale decoder department. It is a barebones decoder, with no fancy features; even so it is one of the largest decoders in this lineup. The low price helps to mitigate the lack of features. Better yet, NCE has an interesting special offer: you can get an Z14SR (or any other NCE decoder) for the low, low price of $12 (includes S&H) + a dead decoder from any manufacturer. Interesting!
Summary: A bit large, and devoid of features, but it can be had quite cheaply. Nevertheless, you are probably better off looking at other decoders first.
Links: Links: NCE website, Z14SR manual.
TCS M1
TCS, unlike other decoder manufacturers, has a fixed feature set used across their entire product line. The M1 features 3-step acceleration and deceleration, allowing for very fine-tuned acceleration profiles. If you like the M1, but need more functions, then the M3 and M4 are precisely the same, but with 3 and 4 functions, respectively. The M1 is a solid decoder, but it’s large relative size—it is the largest decoder in the lineup outside NGDCC’s ungainly offerings—prevents it from getting a recommendation. That said, the M1 has a reputation for being bullet-proof: A TCS rep told me that you could stomp an M1, and it should still function afterwards. If you are prone to frying decoders—as I am—then the M1 may well be a very good choice, despite its size.
Summary: The M1′s has a good feature set, and is quite robust, but for the price, the M1 is too big to recommend.
Links: TCS website, M1 manual.
Zimo MX620
The Zimo name has a reputation for quality in Europe, but is largely unknown in North America—their products aren’t easy to get ahold of. Like many of the other European offerings listed here, the MX620 brings the kitchen sink, including constant stopping distance and RailCom, but also a variety of fairly esoteric features, such as the ability to transmit CV information via an infrared LED, or to power animations, such as pantograph deployment, via a smart servo. All these features come at a price, however.
Summary: A small decoder packed with tons of esoteric but intriguing features, and with a commensurate price.
Links: Zimo website, MX620 manual.
ESU LokPilot micro v3.0 DCC
The LokPilot series of decoders include the kitchen sink—most work on DC, DCC, and Selectrix, all while providing a full feature set. This particular decoder has been pared down to just DCC, however, to save money and space, but it still has the full feature set, including constant stopping distance and RailCom. Still, this feature set comes at the cost of increased price, and increased size. The LokPilot is the second most expensive decoder, and the second largest (of those available outside Japan).
Summary: The kitchen sink requires space and money. Unless you need one of the specialized features offered, there are better choices.
Links: ESU website, LokPilot micro v3.0 DCC manual.
Uhlenbrock 73400
The Uhlenbrock 73400 is the smallest decoder readily available in North America (but cf. CT Elektronik’s entries), but the small size comes at the cost of features. Uhlenbrock seems to have a solid reputation for building reliable decoders. If size is critical, this is your decoder. However, there are other decoders almost as small that are less expensive and have more features.
Summary: A solid entry, but the high price tag makes it the best choice only for those who have critical size constraints.
Links: Uhlenbrock website, 73400 manual.
Lenz Silver Mini & Gold Mini
The Gold Mini and Silver Mini have the same tiny size—the third smallest in this lineup—, nearly the same feature set. The Gold Mini manages to fit a large range of features into its small size, including constant stopping distance and RailCom. Indeed, the Gold Mini is gets a full 4-star rating for its combination of features and small size. One feature that stands out is its short-circuit protection: It is protected against accidentally shorting the motor or a function to the rails, and can even tell you what is shorting out by reading a CV. This makes it a good choice for the clumsy or inattentive installer (like me!)
The Silver Mini has the same feature set, sans the SUSI interface (whatever that is)—and sans $15. The new Silver Mini-S (ask for it by name!) now includes RailCom, unlike older Silver Mini models. The robust feature set, short-circuit protection, and not quite exorbitant price rate it a recommendation.
Summary: Lenz makes outstanding decoders, with a price to match. If you are willing to pay that price, these decoders offer a great feature set in a fairly small size. The Silver Mini in particular is recommended.
Links: Lenz website, Silver Mini manual, Gold Mini manual.
CT Elektronik DCX75D & DCX74zD
CT Elektronik now produces the smallest decoder and the thinnest decoder on the market, the DCX74zD and DCX75D, respectively. The DCX74zD is an amazingly small 7mm x 9mm—it is as long as most decoders are wide. Moreover, these decoders are renown for their low-speed capabilities—a nice touch for smooth station stops. Both decoders are also reasonably inexpensive—however, they are hard to get outside of Europe, and so may yet not be the best bet for the North American or Australian audience.
However, it seems achieving the tiny size comes at a price: According to this discussion, they cannot be programmed in paged mode, but only in direct mode. I do not know if they can be programmed in operations mode.
Summary: Absolutely tiny: The DCX74zD can be hidden just about anywhere, making this ideal for cramped motor car installations—recommended. The thin size of the DCX75D isn’t quite the bonus for motor cars, but it is still a nice decoder generally.
Links: CT Elektronik website, DCX74zD manual (German).
Digitraz DZ125
Digitrax has built a reputation for building reliable decoders, and the DZ125 is no different. The DZ125 is a middle-sized decoder compared to the others in this lineup—making it nevertheless reasonably small for most installations. The feature set is basic, although, like all Digitrax decoders, it does provide Transponding. The DZ125 does provide protection against shorting the motor to the rails, which can be very helpful in delicate installs. But low price more than makes up for a lack of fancy features.
Summary: Cheap, reliable, and reasonably small. Recommended.
Links: Digitrax website, DZ125 manual.
Kato EM13
This decoder is specially designed to fit into Kato’s line of “DCC Friendly” motorized rail cars. It fits into a hidden slot inside the frame, making it totally invisible—and so size is, for these models, unimportant. Since these are designed by Digitrax, they have exactly the same feature set—pretty basic, but includes Transponding, a nice touch for those who use it.
For other models, the EM13 isn’t quite as good—hence the split ratings. The strange shape (it’s not rectangular, but more fork-shaped) makes installations perhaps a little awkard; it’s still small enough for most uses. However, the EM13 is also the cheapest decoder in the lineup, making it an attarctive option nevertheless.
Summary: If you have a Kato “DCC Friendly” model, this is the way to go. Recommended in those circumstances.
Links: Kato Japan website, EM13 manual.
Boring Explanations
Stars
A decoder’s rating is calculated by considering equally the number of desrable features offered, and the size of the decoder (width x length). Price is not used to computer the rating.
☆☆☆☆ Do not use. Unsuitable for cab cars.
★☆☆☆ Adequate. Suitable for cab cars, but you could do better.
★★☆☆ Fine. Suitable for cab cars. Often will have the best feature set for the least price.
★★★☆ Good. Well suited to cab cars. Has more or better features than most.
★★★★ Perfect! An ideal decoder for cab cars. Has most or all of the best features, but is often also the most expensive.
Price per Star
This is the ratio of the decoder’s price to it’s rating in stars. The number is a rough guide to the cost-to-benfit ratio. Lower numbers represent a better cost-to-benefit ratio; higher numbers represent a worse cost-to-benefit ratio.
BEMF
Back EMF (BEMF) is a method for regulating the motor speed for smooth low-speed operation, and maintaining constant speed up and down inclines. It works by inferring the motor’s speed by measuring the amount of feedback generated by its rotation—called back EMF—and adjusting the voltage up or down to maintain a constant speed. This feature is critical for low-speed operations, including smooth acceleration and deceleration from and to a full stop.
Fancy Momentum
All the decoders surveyed offer basic linear acceleration and deceleration, but some manufacturers go a step further. TCS offers 3-step acceleration and deceleration curves for non-linear momentum. This feature is nice for simulating smooth and realistic-looking station stops and starts.
Lenz and ESU offer a feature called “constant stopping distance”, which, when active, varies the deceleration term to bring the model to a stop within a fixed distance, regardless of the speed of the model. This is great for automating station stops, because you will know the distance from the station throat to the stopping point, but you might now know just how fast a model is traveling when it enters the station throat.
Bidirectional Communications
RailCom and Transponding are two different systems of bidirectional communications over DCC. Normally, DCC is a one-way signal: From the command-station to the decoder. There is normally no method for DCC decoders to respond. RailCom and Transponding are methods for the decoder to send a response to the command-station. This is really useful for automated control of a layout, but is not a necessary feature to implement basic block occupancy detection, although both methods require a block occupancy detector detector to work. I won’t get into a discussion of the advantages or disadvantages of each system; you can read more about those elsewhere on the Internet.
RailCom is an open standard developed by Lenz and adopted by the NMRA as a Recommended Practice for DCC. That is, it is now an official, if optional, part of the DCC specifications. RailCom responses can be detected by a Lenz LRC130 RailCom detectors and reported to a computer via the Lenz LRC135 RailComBus USB adapter.
Transponding is Digitrax’s proprietary standard for bidirectional communication, and is currently only implemented in Digitrax decoders and Kato decoders designed by Digitrax. Transponding responses are detected by a Digitrax RX4 detectors, which must themselves be attached to a Digitrax BDL168 block occupancy detector. Transponding events can be communicated to a computer via the Digitrax PR3 LocoNet USB adapter.
Maximum Current Ratings
The current rating of a decoder tells you the largest load you can connect to the decoder. Each light, motor, speaker, etc., draws a certain amount of current; attaching too many will cause the decoder to overheat and perhaps even die.
A manufacturer often lists two or more different current ratings. A current rating is either a continuous rating or peak rating.
Continuous Total Current is the total amount of current that the decoder can supply for all functions combined over an indefinite time period. The sum of the current draw of all lamps must not exceed this amount. This may limit the number of lamps or other loads you can attach to the decoder.
Peak Total Current is the total amount of current that the the decoder can supply for all functions combined for short bursts. This is particularly important for motor decoders, where the stall current of the motor (the amount of current the motor draws when it is stalled or locks-up) must be less than this number.