Need DCC advice and wiring help

[Anonymous]

Hello Everyone,
I'm doing an N-Scale layout and want to use DCC. I have some questions on this matter. First, do you still need to install feeder wires thru out the layout when using DCC? Second, when doing a reverse loop do you still need to install feeders within the loop or will the reverse loop module be enough to detect the loop and change the polarity or do I need both the auto detect and feeder wire?
I'm using Peco code 55 flex with Peco turnouts.
Thank you all in advance for help with this. I'm kind of lost and see all these different modules you can get and use and wonder are they really needed. I want to do this right the first time.

Louie

[Jacktal]

You'll need an extra booster for the loop with its own feeders.For a more complete information,I suggest that you visit Digitrax's website.You'll find everything you need to know on installation.NCE's website is also a good place to visit,or even better,Loy's Toys website.

[nfmisso]

Hi Louie:

First; Jacktal is not correct, you do not need an extra booster for a reverse loop, just a reversing module, any brand will work with any system.

The reverse loop(s) should consist of a section track longer that your longest locomotive, and preferrably longer than your train which has both rails insulated from the rest of the layout. This section should only be connected to the autoreversing module. If it is long, it may require multiple feeders.

Read: http://www.dcctrains.com/tonystips/dccprimer/index.htm

[mls1621]

As an alternative to a reversing module, you might consider using a DPDT switch to manually reverse the polarity.

I've used this method several times and it's very easy to do and is totally dependable.

A Double Pole Double Throw switch has two sets of contacts and internally acts as two separate switches.

The A and B lines for track power are connected to the switch at one end and then crossed to connect to the opposite end. The track power comes from the center/common leads.

In one position, the switch feeds the reverse loop to match that of the entering locomtive. When the locomotive or consist has fully entered the reverse track, throw the switch and the polarity is changed to match the track at the exit.

Honestly I have no experience with an electronic reversing module or how it affects the locomotive, but at the very worst the manual method causes a very slight stumble of the locomotive when the switch is thrown. Most of my locomotives show no effects at all.

By mounting the switch to throw right and left, or in the same direction relative to the reversing track, you can use the lever's position to indicate the reverse loop's polarity.

This method is simple and inexpensive, the switch only costs a few dollars and is virtually fool proof.

I hope I've given you alternative and that this is helpful.

[Jacktal]

Sorry for this one...I never meant to mislead anyone.But now there's something I don't understand.Reading Digitrax's Chief manual(sect. 7.2,p.25) wich states:"If you choose manual operation,power the reverse section with a SEPARATE transformer&use a switch or relay to handle the polarity change......".

I understand the DPDT switch concept,a relatively easy one in fact,but what would be the purpose of the separate transformer if it is not to drive another booster?It is my understanding that only one transfo can be powering the command station,and if a separate transfo is used for the reverse section,what controls throttle within the loop?There's obviously something I don't get right.

For automated polarity reversing,one indeed needs an extra transfo and booster(DB-100)and that part I understand.Could someone turn my lights on?

[mls1621]

Hi, Jacktal,

When I installed the reverse loops described in my earlier post, I just spliced into the main buss as the source for track power.

No separate transformer or other power source was needed.

I first used this method to install a reverse loop on my neighbor's N scale layout and later on my own. Since then, we've built a steel mill module on his layout and used the same method again as the entire steel mill module is a reverse loop, single track in and out.

I've not seen the reference you mention in the DigiTrax manual, but then I've not looked for it either. I can't imagine what the need would be.

[ClinchValleySD40]

Sorry you're reading the manual wrong. One of the real beauties of DCC is the auto reverse available. Check out Tony's Train Exchange. His PS Reverse is great.

And you do NOT want to use DPDT manual switches, that defeats the purpose of the DCC auto reverse. And you do NOT need a second booster. And you will want to put drop feeders within the loop.

It's all very simple. Just cut the main buss wire where you want the loop. Install the reverse module, kind of like a splice, so the main buss comes in and out of it. Do not connect the far end of the buss to anything, just wire nut it off and let it hang.

[nfmisso]

QUOTE: Originally posted by Jacktal

There's obviously something I don't get right.

For automated polarity reversing,one indeed needs an extra transfo and booster(DB-100)and that part I understand.Could someone turn my lights on?

You do NOT need a seperate booster or transformer for the reversing module. The autoreversing module is placed between the booster and the reversing loop section. That is all there is to it, nothing complicated, no manual thing to switch.

The autoreversing module has four connections, plus some have a ground. Two inputs that are connected to the output of the booster, and two outputs that are connected to the track. The autoreversing module gets all of its power (which is next to nothing) from the booster.

The manual of referencing is not up to date, and apparently does not reflect the availability of autoreversing modules from several suppliers. These boxes are NOT dependent on the manufacturer of the DCC system, all work with all.

[SteelMonsters]

In DC, you would cross plolarity resulting in a short between the DC terminals when a train runs over one of the gaps. The problem is the loco will move in a different direction on different polarity.

In DCC since it's square wave AC, the two phases don't matter, the loco will run the same on opposite phase. The problem as with DC is that if the phases are different, then it will short the Booster leads when a loco hits one of the gaps.

There are many many ways to deal with it. All you need in either case is the power to be in the same polartiy. when a loco is running over the gap.

The reversing unit's I'm familiar with take the regular track power and when there is a short in the reversing section, it simply reverses it. It happens faster than boosters can react. If there is a short the power will reverse but then power will be cut shortly after by the booster.

Problems can occur if your not careful. If two opposing gaps are being crossed by powered cars/locos simotainouly, then reversing doesn't stop the short. This can happen if you have a short reversing block, if you have two trains the cross a gap simotainously, if you use lit cars or locos mid train and that car hits one gap with the one of the locos. It's not a real hard concept, but it's a bit abstract

If it helps you anymore, you can sketch your reverse areas or enitred track layout. Just have two rails and go around adding +'s and -'s, or 1's and 0's. If opposites find a section to create a reverse loop, and make sure it's longer than however many locos/powered carss you will run together.

For hot swapping (switching polarity while a running train is on the track) semiconductors switch much faster than a toggle switch or relay. Unless you enjoy beating on a poor toggle switch, autoreverers are the way to go for this application.

[mls1621]

When I proposed the Toggle swtch method, it was to give an inexpensive alternative to the reversing module.

Using this a toggle switch, a reverse loop can be implemented for a fraction of the cost of a reversing module. It works and I have money to spend on rolling stock or structures.

I'm fortunate in that I have enough space to run from staging, through the visible portion of the layout and back to staging. My reverse loop is used to turn trains and thus change the operation.

The PM4 from DigiTrax is listed for $79.95, the corresponding Lenz unit lists for $57.00 and MRC has one for $34.98. A $5.00 DPDT toggles switch leaves alot left over for something that might be critical for the layout.

[CP5170]

I use a DPDT for the reversing loop in the staging area with a Digitrax system.