Double Track with DCC

[changkh]

Currently, I am running KATO trains on two independent tracks each on one power pack so I can control them independently.

If I go DCC, do I still need 2 DCC or will 1 do the job?

[kvp]

With DCC all tracks _should_ carry the same signal. This means just feed both loops from the same central. (usually done with an Y cable)

 

ps: If there is a place where a train can go from one loop to the other, then the DCC signal _must_ be the same, otherwise a crossing train will create a short circuit. (very much the same way as a crossing train in analog would create a short if the polarities/directions don't match).

[Ochanomizu]

Currently, I am running KATO trains on two independent tracks each on one power pack so I can control them independently.

If I go DCC, do I still need 2 DCC or will 1 do the job?

 

Hello,

 

Short story: 1 DCC system will do the job.

 

Longer story:  Take a look at the Digitrax Nemo Junction Case Study.  It shows a variety of different DCC features you can add to your layout.  You don't need all of these features.  Importantly, the case study is a double loop similar, I suspect, to your layout.  

 

I use Digitrax because they manufacture the Kato decoders, but other brands offer most of the same features and will work with the Kato decoders.

 

If you just want to control your trains with a throttle then I suggest you will need something like the Digitrax Zephyr Xtra.  Add a PM42 with one zone for each loop to manage any short circuits.  Add a DS64 to cover up to 4 turn outs with routing.

 

Hope that helps for a start.

[changkh]

With DCC all tracks _should_ carry the same signal. This means just feed both loops from the same central. (usually done with an Y cable)

 

ps: If there is a place where a train can go from one loop to the other, then the DCC signal _must_ be the same, otherwise a crossing train will create a short circuit. (very much the same way as a crossing train in analog would create a short if the polarities/directions don't match).

 

Thank you, kvp. I found KATO has a 3-way extension cord.

One question, if I use such a Y cable with a single power source and feed both loops, does it mean each loop gets half the current and hence the trains will run slower?

[kvp]

Thank you, kvp. I found KATO has a 3-way extension cord.

One question, if I use such a Y cable with a single power source and feed both loops, does it mean each loop gets half the current and hence the trains will run slower?

 

A DCC system (even the most basic one) will have enough current for 3 or more trains to run at the same time. So as long as you don't run more trains at the same time than your central could support, then each train will have enough current. The voltage will be the same (the Y cable creates a parallel connection) and the maximal speed is dependent on voltage, while current consumption is based on the actual load. Ideally your power source and central should be able to supply more than 2 trains as long as each one is connected in parallel. The Kato 3 way extension cord ensures this. Just watch the polarity as the DCC signal should be at the same polarity on both loops if you have turnouts between them. (if this is not the case, one of your feeders should be flipped around)

[changkh]

Hello,

 

Short story: 1 DCC system will do the job.

 

Longer story:  Take a look at the Digitrax Nemo Junction Case Study.  It shows a variety of different DCC features you can add to your layout.  You don't need all of these features.  Importantly, the case study is a double loop similar, I suspect, to your layout.  

 

I use Digitrax because they manufacture the Kato decoders, but other brands offer most of the same features and will work with the Kato decoders.

 

If you just want to control your trains with a throttle then I suggest you will need something like the Digitrax Zephyr Xtra.  Add a PM42 with one zone for each loop to manage any short circuits.  Add a DS64 to cover up to 4 turn outs with routing.

 

Hope that helps for a start.

 

Thank you, ochanomizu.

I am just a casual hobbyist new to n-gauge for now. And due to space and time constraint, I assemble the tracks and dismantle them after every play.

The reason I am looking at DCC is to control my trains with a single controller rather than having multiple power packs.

 

I was also looking at KATO's D102 which looks like the Digitrax Zephyr Xtra that you mentioned.

One of the features is able to use additional DC power packs as throttles via the jump ports. What is the purpose of that? To be able to control 2 trains simultaneously?

[kvp]

I was also looking at KATO's D102 which looks like the Digitrax Zephyr Xtra that you mentioned.

One of the features is able to use additional DC power packs as throttles via the jump ports. What is the purpose of that? To be able to control 2 trains simultaneously?

Yes. Many european DCC centrals already have two knobs for controlling two trains at the same time. (assuming that one person has two hands) The idea with the jump throttles is the same. Some centrals on the other hand don't have built in controllers at all and you have to add external handheld throttles. Some people like to have one DCC controller and control all trains with it, by constantly switching from one train to another. I prefer to have a separate controller for each train and put down one and pick up another when i switch trains, just like with analog controllers.

 

How many power packs do you use right now? As adding DCC to an existing fleet of trains could cost a lot of money, depending on the number and type of the trains in question. DCC really shines when you want to run more than one train (or locomotive) in the same block (loop). If you are only running trains on fixed and mostly isolated loops, then adding DCC (especially with japanese trains) is not always the best (and cheapest) answer.

[changkh]

How many power packs do you use right now? As adding DCC to an existing fleet of trains could cost a lot of money, depending on the number and type of the trains in question. DCC really shines when you want to run more than one train (or locomotive) in the same block (loop). If you are only running trains on fixed and mostly isolated loops, then adding DCC (especially with japanese trains) is not always the best (and cheapest) answer.

I currently have two power packs. I'll probably put on hold first; as you mentioned, it may not be a worthwhile investment for me at this point of time.

But thanks for your advice, it'll definitely be helpful if I decide to go DCC in future.

Now I'll try to read up on how to run trains on double track with crossover using power packs.

[kvp]

You just run them. The Kato single and double crossovers are already isolated. If you turn both packs to the same direction and speed while crossing with a train, it will just work.

 

For turnouts that are not isolated, you have to use the black isolating joiners that come with them to isolate both rails between the two loops. This way only the tracks (and trains) go from one loop to the other, but not the power.

[changkh]

You just run them. The Kato single and double crossovers are already isolated. If you turn both packs to the same direction and speed while crossing with a train, it will just work.

 

For turnouts that are not isolated, you have to use the black isolating joiners that come with them to isolate both rails between the two loops. This way only the tracks (and trains) go from one loop to the other, but not the power.

 

Yes, I have this booklet that comes with my V11 unitrack and it says the same thing.

I can understand both packs have to be in the same direction but why speed as well?

[kvp]

So the train doesn't suddenly jump when the motor car crosses over the isolator. It doesn't have to be exact, just more or less the same speed.

[gavino200]

 Add a PM42 with one zone for each loop to manage any short circuits.

 

 

 

I'm considering doing this. From an electrical point of view it gives me what I need and want. But I have a few question for you about how you actually use this thing on your layout if you don't mind.

 

 

Where does this unit actually go? Is it in plain sight? It's pretty ugly. If it's hidden you can't see the LEDs 

 

Does it make a noise when there's a short? Different noise for each district? If not, how do you know what district is shorted? (assuming you haven't just seen your train shut off on that line.

 

How do you reset it? are there manual switches on the board?

 

How do you set it up? Does your DCC wire that otherwise would go to the track connect into it? Or does a phone type jack connect to one of those two jacks that I can see on the board? Just like how a booster would be connected to the a control center.

 

What do you like about this unit? What do you not like about it?

 

Is it possible to hide this unit, but run some wires to a visible LED display that would identify which district is shorting?

 

Thanks.

[kvp]

The phone jacks are loconet connectors and they should be used to daisy chain the circuit to the loconet based centrale, so problem reporting and control works. There is an edge connector on the back, that can be inserted into a breakout board, where the main track power in and block power outputs are connected. You have to add here the external power and the main safety ground too. The board usually goes below the layout and instead of the leds, you can check the state if your central supports it. If not, then you might want to use a different circuit, that doesn't use loconet. One alternative way to mount it is in the frame of the layout with the leds and loconet looking outside and the cable connections on the back with the breakout board, as this allows you to see the leds without using loconet for error reporting. The exact connections and the back connetor pinout are described in the manual.

 

http://www.digitrax.com/static/apps/products/power-management/pm42/documents/PM42.pdf

[Ochanomizu]

Hello,

 

Firstly, as KVP suggested, please read the manual.

 

Where does this unit actually go? Is it in plain sight? It's pretty ugly. If it's hidden you can't see the LEDs:  Mine is under the bench.  I rarely look at it.

Does it make a noise when there's a short? Different noise for each district? If not, how do you know what district is shorted? (assuming you haven't just seen your train shut off on that line.  Only a click.  There is no noise to identify which circuit.

How do you reset it? are there manual switches on the board?  It is automatic.

How do you set it up? Does your DCC wire that otherwise would go to the track connect into it? Or does a phone type jack connect to one of those two jacks that I can see on the board? Just like how a booster would be connected to the a control center.  See the manual.  You don't need LocoNet or other Digitrax products but you do need a DCC command station.

What do you like about this unit? What do you not like about it?  I like it because it does the job of protecting my trains.  

Is it possible to hide this unit, but run some wires to a visible LED display that would identify which district is shorting?  PM42 sends messages to the command station when there is a short circuit, when it is cleared, and when a train enters an autoreversing loop, so I don't need a visual LED display.  However, you can do a simple version by connecting a simple circuit consisting of a Schottky Diode, Resistor and LED to each circuit.  If illuminated, the circuit has current.

[changkh]

So the train doesn't suddenly jump when the motor car crosses over the isolator. It doesn't have to be exact, just more or less the same speed.

 

Is it because the two sets of wheels on each side of the isolator getting different current and hence speed that causes the jump?

 

I did some read up on KATO's 20-210 double crossover but couldn't find it's instruction manual online to understand more.

I am thinking of using it in my V11 double track set which effectively just like a inner and outer loop layout.

 

The V11 comes with a double feeder, I have two power packs and also 2 point switches from my M2 set.

KATO mentioned that 4 feeders are required but if it is a loop layout, 2 will suffice which translates to 2 power packs.

 

The double crossover comes with a cable which I assume is for the point switch.

With my current inventory, am I good to run with the double crossover?

[kvp]

More or less yes, there could be a jump when the two throttles start and stop sharing control. Works, but looks ugly. Setting the same speed makes it smooth.

 

The double crossover has double isolators between the two loops and single isolators in the straight direction. The latter is used for double track terminuses, but not needed for loops. The general good practice is to add one feeder to each end, but if you have loops and add the two feeders to the opposite side of the loops, then you only need one for each loop. This allows adding one crossover to a basic double track set easy. If you have a station on the opposite side, then just try try to move the feeder as far as possible from the crossover to get a more even power distribution. For smaller layouts, this works fine. (for larger ones or if you have more than one crossover, feeds on both sides are a must)

 

The double crossover has one cable which is for the point motor, so you need one switch for it, which leaves you with one extra swtich for another turnout. If you build a bypass track from the two turnouts and use an Y cable to move them at the same time with a single switch, then you can control both the crossover and the two turnouts with only two switches.

[changkh]

I just got the double crossover and used it with my V11 set.

However, the train tends to slow down as it moves further away from the double crossover.

I ran the train at the slowest possible speed to make it obvious. As can see from the first two videos, the train lights up after passing the double crossover. As it moves away, it gets dimmer and by the time it reaches the opposite loop, the lights are off. Is this normal?

I ran the train at full speed in the third video for comparison. It is not so obvious but can still feel the same.

1

https://www.youtube.com/watch?v=wmWylgUZBjE

2

https://www.youtube.com/watch?v=RK8gYDEGAgw

3

https://www.youtube.com/watch?v=qG_rU7tc2FI

[kvp]

This is normal, as the crossover has isolators in the inner through rails, not just in the crossover direction. Since you feed power only from one side, the other side gets its power across the whole loop. The quickest fix is to feed from the opposite end of the loop, so the farthest point will be the crossover itself. This cuts the feed distance and power loss to half and the turnout will have roughly the same voltage drop on both sides, so you won't notice it.

 

Voltage drops like this could be eliminated with multiple feeders. One solution is to feed the layout on all sides of the turnout, so one feeder pair in one loop and one pair on the other. This needs two feeder pairs, so 2 extra feeders and 2 extra feeder Y cables. I would say one feeder for every 2 meters is a safe bet for floor running.

 

Another trick is to add jumper cables from the inner side of the crossover to the other inner side on the same loop. This requires two jumper cables with unijoiners soldered onto both ends. The voltage drop will be still be present, but you won't see it as the worst location would be across the feed point and it will be gradual. Just like if you moved the feeders to the other side of the loop.

 

If you have or plan to add a station to the other side with bypass tracks, then adding multiple feeders to the middle of the 180 degree curves would also work, as both the crossover and the bypass tracks would be at the same distance from the 2 feed points.

[changkh]

Thanks KVP, I will try to move the double crossover to the other end so that it is directly opposite the double feeder. I am just curious how would the voltage drop so much over a mere few meters. Some kind of internal resistance present in the rails?

[Darklighter]

Thanks KVP, I will try to move the double crossover to the other end so that it is directly opposite the double feeder. I am just curious how would the voltage drop so much over a mere few meters. Some kind of internal resistance present in the rails?

I suspect the UniJoiners. ;)

[cteno4]

Yes check the unijoiners. You can gently squeeze them tigheter with a small pair of flat end pliers or just try trolacing a few in the area of the voltage drop. They are pretty cheap and worth it to get thing working well.

 

Jeff