DCC Decoders for Motor Cars

[CaptOblivious]

This thread is for keeping track of good DCC decoders to use in Motor Cars, or any other car that has motor, but few or no functions, as is often the case at in the middle of an EMU or a bullet train. I'll keep this list updated as people report in.

DE22x2

DE25x0

M1

MX620

LokPilot micro v3.0 DCC

73400

Silver Mini

DCX75D

Z2

DCX74zD

DZ125

Gold Mini

EM13

Manufacturer

NGDCC

NGDCC

TCS

Zimo

ESU

Uhlenbrock

Lenz

CT Elektronik

TCS

CT Elektronik

Digitrax

Lenz

Kato

Price

$32

$23

$32

$60

$55

$46

$45

$43

$35

$33

$25

$60

$22

Height

1.9mm

2.4mm

3.43mm

2.5mm

3.5mm

2.4mm

2.8mm

1.4mm

2.79mm

2.6mm

2.86mm

2.8mm

?

Width

9.3mm

11.6mm

9.12mm

9mm

9mm

7.5mm

9mm

7.2mm

6.6mm

7mm

8.7mm

9mm

?

Length

29.3mm

24.4mm

14.4mm

14mm

13.5mm

10.8mm

11mm

11mm

12.95mm

9mm

10.6mm

11mm

?

Total Area

272.49mm²

283.04mm²

131.328mm²

126.0mm²

121.5mm²

81mm²

99mm²

79.2mm²

85.47mm²

63mm²

92.22mm²

99mm²

?

Functions

2

0

2

2

2

2

2

2

2

4

2

2

0

BEMF?

◯

◯

◯

◯

◯

◯

◯

◯

◯

◯

◯

◯

◯

Fancy Momentum?

✕

✕

◯

◯

◯

✕

◯

✕

◯

✕

✕

◯

✕

Transponding?

✕

✕

✕

✕

✕

✕

✕

✕

✕

✕

◯

✕

◯

RailCom?

✕

✕

✕

◯

◯

✕

✕

✕

✕

✕

✕

◯

✕

Max Current (cont. total)

500mA

1000mA

1300mA

800mA

750mA

600mA

500mA

1000mA

1000mA

1000mA

1000mA

500mA

1000mA

Max Current (peak total)

2000mA

3000mA

2000mA

2000mA

800mA

2000mA

2000mA

2000mA

1250mA

800mA

1500mA

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.

[Bernard]

Great thread!
Don - I have a question, in an earlier thread you were one of the first people I know that got the Kato EM13. As I recall there were some problems, would you recommend that decoder? It looks very easy to install and price wise might be the least expensive on the list.

[CaptOblivious]

The EM13 is…well…adequate. I don't know that I'd recommend it, but I also wouldn't recommend against it, as it does have its niche (cue drums).

Pros: Inexpensive, in new Kato models it's completely hidden, offers Digitrax Transponding if that's your thing.

Cons: Very minimal feature set (no 4-digit addressing!), no CV read-back even in service mode (on the programming track).

Here's my original, if rather terse, review of the feature set of the EM13
http://www.jnsforum.com/index.php/topic,26.msg770.html#msg770

[Martijn Meerts]

I guess whether a decoder is adequate or superior is down to personal taste a lot. For example, I think the Lenz Gold (and the new version of the Lenz Silver) are superior, considering they do exactly what I want, and for what they can do, I don't think they're that expensive (especially not the Silver.) Digitrax decoders might be great and much better than Lenz (just as an example, I don't know much about Digitrax), but Digitrax is hard to get in Europe, so for me it wouldn't be a superior decoder until they find some european distributor.

Maybe we need an "Excellent" or "Great" or something in the list to distinguish between adequate and good decoders ;)

[CaptOblivious]

I guess whether a decoder is adequate or superior is down to personal taste a lot. For example, I think the Lenz Gold (and the new version of the Lenz Silver) are superior, considering they do exactly what I want, and for what they can do, I don't think they're that expensive (especially not the Silver.) Digitrax decoders might be great and much better than Lenz (just as an example, I don't know much about Digitrax), but Digitrax is hard to get in Europe, so for me it wouldn't be a superior decoder until they find some european distributor.

Maybe we need an "Excellent" or "Great" or something in the list to distinguish between adequate and good decoders ;)

Probably so. The list as is is a starting point for a discussion.

While I agree that the Lenz Gold Mini is an amazing decoder generally, I'm not convinced it's the best possible decoder for installation into motor cars. It could be smaller (fewer functions) and cheaper (lots cheaper). What the Digitrax and TCS decoders lack in features they make up for in price. I just haven't seen a decoder that—to me—strikes the right balance for the motor car of an EMU.

People will disagree :D

So, perhaps I should avoid ranking them, at least beyond a basic sufficient/insufficient classification scheme? Or maybe a more multi-dimensional ranking system so that readers can pick and choose based on their personal preferences? That sounds better, actually.

[CaptOblivious]

I've updated the information above to be consistent with this post on my blog:
http://akihabara.artificial-science.org/dcc/dcc-for-motor-cars/

I've left the editorializing out this thread, and reserved the recommendations for my blog :D