DCC Decoders for Cab Cars/End Cars

Stars

☆☆☆☆ 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.

Directional Lighting

When a prototypical MU is moving, the headlights at the front of the train are on, and the taillights at the rear of the train are on. When the train switches direction, the headlights and taillights switch too. A decoder that supports directional lighting will automatically switch the headlights and taillights depending on the direction of travel set by the throttle, with no user intervention necessary. This is a very important feature for a function decoder used in cab cars to have.

Bi-Polar Circuit Capability

A bi-polar circuit is simply a circuit with two leads that behaves differently depending on the direction of current across the leads. The directional lightboards in cab cars are bi-polar circuits: When the current flows one way, the headlights come on. When the current flows the other way, the headlights go off, and the taillights come on.

A DCC decoder function lead can only control one light circuit at a time, because they can only generate current flow in one direction. Thus, the lightboards must typically be cut apart into two distinct lighting circuits before a decoder’s function leads can be attached. However, some lightboards are too small or delicate to easily cut apart in the way needed. In these cases, a decoder that can provide current flow in two directions can be connected directly to the leads of the lightboard without having to cut it apart. This is a tremendously helpful feature, but is only rarely necessary.

Dimmable Headlights

As in the United States, Japanese rules of operation require trains to dim their headlights when passing or standing at passenger stations. Although a subtle feature, many modelers enjoy prototypical lighting effects in their trains. Typically, a decoder that supports this feature will dim the lights when F4 is pressed. Any function decoder that supports “Rule 17″ operation of the lights will support this feature.

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 Lenz's semi-proprietary standard. 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 oddts 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 odd die.

A manufacturer often lists two or more different current ratings. A current rating is either for each function individually, or the total current for all functions combined. Moreover, a current rating is either a continuous rating or peak rating.

Continuous Current per Function is the amount of current a decoder function lead can handle over an indefinite time period. For example, if the literature claims a 125mA continuous function current rating, then you can attach a lamp that draws up to 125mA to that function, and leave it on as long as you please.

Peak Current per Function is the amount of current a decoder function lead can handle for short bursts. Incandescent lamps, when they first turn on, have an inrush current that is ten times the current draw of that lamp. For example, a lamp that is rated as drawing 50mA will actually draw 500mA very briefly when it is turned on. So this rating is important to know when you are using incandescent lamps. LEDs do not have a significant inrush current.

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. Unless you will be using a large number of incandescent lamps (see above), this number is relatively unimportant for function decoders.

Well, I just posted this to my blog:

http://akihabara.artificial-science.org/dcc/dcc-for-cab-cars/

Perhaps I should update this page accordingly ;)

Shuhei Nagasue-san, the head of NGDCC, sent me a very nice email last night, telling me that I've incorrectly undersold his competitor's product! No American company would ever do that.

Anyway, he point out two inaccuracies in my description of the FL12: First, it does support 4-digit addressing. Indeed, reviewing the manual, it clearly does. I'm not sure where I got that it didn't. Second, it does support CV readback in the programming track, but that the loads usually attached are too small to be detected by the programmer, so in practice they cannot be readback.

The lack of 4-digit addressing struck me as a massive failure on the part of the FL12. So, I have bumped up its rating in light of this information.

I also thought it didnt support 4 digit addressing.

I am going to have to check this one out and get back to you.

Attached instructions for FL12 describe it only as having 2 digit addressing

I thought so too!

But, look again at the top of page 2. The bit we focused on is about CV01, which is the 2-digit address CV.

I managed to program my E231-500, motor car and cab cars, with 4-digit addresses last night!

The trick is to manually set CV17 and CV18, (and then configuration CV29, too) rather than rely on your programmers automatic address setting feature.

You will find this link helpful:

http://www.ruppweb.org/Xray/comp/decoder.htm

Capt O your a genius, shows how much I rely on the auto features of the system instead of RTFM.

My N700 now has a more intuitive address, now if I can get the N in there somehow.......

This means the FR11 is back in the running for interior lighting as well.......... That's gonna hurt, I need 130 of them ::)

Capt what do you set CV29 to?

Capt what do you set CV29 to?

38 will do (same settings as default value of 6, except for 4-digit addressing instead of 2-digit)

(basically, just add 32 to whatever value you were using before, if not the default)

I have just finished installing my first TCS FL4 for end car use into a Kato 800 series. My install is almost identical to Martijn's, so I won't bother to upload it. I made a discovery though, I thought I had fried the white led. I did a quick confidence check as soon as I finished soldering to make sure all was good before closing up and programming. The white led would not work.

I pressed on and started to set the CV's thinking I would change the led when finished. Suddenly the white led started working. It appears that when using the single resistor on the light board with the blue wire instead of separate resistors on each function, the red led steals all the power if they are both set to on.

Also note that there are 2 lots of CV's for each function. This is what I ended up with.

CV51=0  CV35=1

CV52=16  CV36=2

This gives fwd on green and rev on purple

I pressed on and started to set the CV's thinking I would change the led when finished. Suddenly the white led started working. It appears that when using the single resistor on the light board with the blue wire instead of separate resistors on each function, the red led steals all the power if they are both set to on.

That's interesting, but I suspect more a function of the lightboard design than the decoder.

I have noticed that the FL4 takes a little bit to find its feet? I don't know how else to describe the phenomenon, but I've see it with several decoders: The decoder doesn't appear to work until it's been on the track for about 10-20 seconds. Meanwhile you're fiddling with the controls and the CV programming, when suddenly, after mucking about with CVs you put them back where they were originally. Then the damned thing works.

Does anyone else have this experience, or is it just me?

Anyway, I wonder if that wasn't what was going on in your case, mrpig. Glad to see it's working out now.

Cap - I have done some thinking on this led thing, didn't that tax the grey matter. Been over twenty years since I did any circuit theory.

It is all to do with the light board design and the different turn on voltages for red and white led's.

Any decoder will give the same results. It was just more obvious with the FL4 because of its default programming.

I will draw up the circuit in a new thread and write up the theory to go with it for anyone interested

I wondered if it was something like that (hence the comment that it was more likely the lightboard than the decoder), but I don't know enough to articulate what I was thinking. I would love to see this phenomenon clearly written up.

Capt

Do you know anything about the TCS FL2?

I assume that it is the same as the FL4 but only with 2 functions. I tried to read the manual for it and it was impossible to decpher whether it was directional (http://www.tcsdcc.com/Additional.pdf).

By directional I mean plainly and simply that it will control 2 lights (ie. the headlight and the taillight) by automatically:

- turning the headlight on and turning the taillight off when moving forward; and

- turning the taillight on and turning the headlight off when moving in reverse?

Will the TCS FL2 or FL4 do this?

Capt

Do you know anything about the TCS FL2?

I assume that it is the same as the FL4 but only with 2 functions. I tried to read the manual for it and it was impossible to decpher whether it was directional (http://www.tcsdcc.com/Additional.pdf).

 

By directional I mean plainly and simply that it will control 2 lights (ie. the headlight and the taillight) by automatically:

- turning the headlight on and turning the taillight off when moving forward; and

- turning the taillight on and turning the headlight off when moving in reverse?

 

Will the TCS FL2 or FL4 do this?

 

Both will do exactly what you want. I am very pleased with my first FL4, and will be buying more. The FL2, oddly enough, is quite a bit larger, which is why it didn't make it into this review.

I'll post some sample CVs for TCS decoders later today.

OK, to program the TCS FL2 or FL4 to have directional headlights, here's how to do it.

First, notice that we'll be using the Green and Purple function leads (mapped by default to F1 and F2 respectively; function-only decoders don't come with White and Yellow function leads).

Suppose that the Green (F1) is wired to the headlights, and the Purple (F2) to the taillights.

To make the headlights (Green/F1) come on when the train is moving forward:

CV51 = 0

And the taillights (Purple/F2) come on in reverse:

CV52 = 16

For the car at the other end, just reverse those values.

Source:

http://www.tcsdcc.com/pdf/Advanced%20X%20Features%20v1.pdf

TCS tries to be helpful, by organizing programming tasks into tables. Table 11 covers assigning lighting effects to function leads. However, there is no one place to get a complete list of all the tables, and sometimes there are different versions of a table (I count at least two and maybe three versions of Table 11 across various literature). Grr. Can get very confusing.

I also remap the green and purple wires on the FL4 so they both operate on F0 just like white and yellow on a normal decoder with motor control. To do this set the following CV's.

CV35=1

CV36=2

I also remap the green and purple wires on the FL4 so they both operate on F0 just like white and yellow on a normal decoder with motor control. To do this set the following CV's.

 

CV35=1

CV36=2

Thanks! Forgot to mention that. Remapping the functions like this does not require you to redo the CVs which select the lighting effect (unlike on Digitrax decoders).

So in order to work just like (say) the kato decoder, I need to program:

CV35=1

CV36=2

To make the headlights (Green/F0) come on when the train is moving forward:

CV51 = 0

And the taillights (Purple/F0) come on in reverse:

CV52 = 16

Is that correct?

You are correct, sir!

So in order to work just like (say) the kato decoder, I need to program:

 

CV35=1

CV36=2

To make the headlights (Green/F0) come on when the train is moving forward:

CV51 = 0

And the taillights (Purple/F0) come on in reverse:

CV52 = 16

 

Is that correct?

you are a scholar and gentlemen ! thank you

And don't forget that if you wired up both end cars identical, you will probably have to add 1 to whatever value you have in cv29 for the tail end car only ( cos its facing the other way ).

Now how about automatic headlight dimming when stopped, aka, rule 17.

Set CV61=16 (dim when stopped)

      CV64= 2-6 for led's, 12-18 for bulbs.  I started at 5 but adjust to your liking.

      CV51=8

Note this is for a FL4. Haven't played with the other decoders yet.

And don't forget that if you wired up both end cars identical, you will probably have to add 1 to whatever value you have in cv29 for the tail end car only ( cos its facing the other way ).

I thought all you needed to do was reverse the purple and green. This last sentence confuses me a little.

Do I also need to add 1 to cv29 if I reverse the purple and green?

And don't forget that if you wired up both end cars identical

No need to change cv29 if you reverse green and purple. Only if both cars are wired exactly the same.

Sorry for the confusion.

my thanks to you also mr pig.