# DCC and Block Wiring



## MichaelE (Mar 7, 2018)

Is block wiring still recommended for DCC as it was for block control using DC?

I ask, because it would allow to isolate an electrical problem by eliminating one block at a time to isolate the problem. Basic electrical troubleshooting, if you will.

I know everyone uses 'drops' for sections of track on a DCC layout, but is this for block control or is it to more evenly distribute AC through the rails because of electrical resistance?

It's something I've been scratching my head over since getting back into this hobby and opting for DCC.


----------



## Mark VerMurlen (Aug 15, 2015)

Blocks are not required for DCC like they were for DC. The reason for blocks in DC layouts was so that you could control which power pack and throttle powered the train in that block. You would have to constantly flip switches as the trains progressed from block to block. None of that is necessary for DCC.

You may still want to have blocks for a few reasons. One reason is if you want to use computer automation for your layout. Blocks are used then to be able to track where your trains are on the layout by detecting which block is drawing power. Another reason is that you may want to isolate certain sections so that if a short occurs in one section, other sections still have power. In this case you'd want to have a power manager for each of these sections that detects short circuits. Another reason is if you have a very large layout with many locomotives and you want to use a booster to supply increased power. In both of these last two scenarios, the blocks are likely to be fairly large, much larger than typical for automated detection or what might have been the practice for DC in the past.

Most people use multiple drops to evenly distribute power and increase reliability.

Mark


----------



## MichaelE (Mar 7, 2018)

Thank you Mark. 

I will be wiring blocks then. I am eventually going to add block signaling and possibly computer control. I have enough of them sitting idle doing nothing so I may as well put them to good use down the road.

Are the blocks wired the same as they would be in DC with one rail wired as common and then insulated joiners on the hot rail separating individual blocks?


----------



## Mark VerMurlen (Aug 15, 2015)

I have a fully computer automated layout with DCC, but I only have experience with my own layout and my own track configuration. There are other people on this forum that have more extensive experience.

Regarding if you should be using a single insulated joiner with common rail, you should read the manual for whatever occupancy detector you're using. I chose to insulate both rails at all block boundaries. This give maximum flexibility since you can always tie one side together if desired/needed. I'm using Digitrax BDL168s for my detection and it has both blocks and sections. If I remember right, it supports common rail between blocks in a section, but sections need to have double insulated rails between them. I didn't want to figure out where sections would occur ahead of time, so that led me to decide to double insulated every block. You'll have to decide what's best for you, your layout, and your hardware.

Figuring out where block boundaries should occur can also be a bit tricky. The train automation software I use has a recommendation that you don't include turnouts within any blocks. I didn't follow that recommendation when I laid my track since I was unaware of it. I included my turnouts in the block on the single track side of the turnout, which as worked out ok for me. Do NOT put a turnout into either of the two blocks on the other side of the turnout unless its a continuation of the same block as on the single track side. I would think that if you're using blocks just for signaling, you would want the turnout to be part of a block because a "dead" area may mess up the signaling hardware, but I could be wrong.

As you can probably tell, you need to think long and hard about where your block boundaries are located because it affects the signaling or computer tracking abilities of your layout. Having to make block boundary changes after the track is down is a real pain.

Mark


----------



## MichaelE (Mar 7, 2018)

Hey thanks a lot for that information. It sounds very important and not something I considered. :smilie_daumenpos:

I'm going to be using Veissmann signaling so I will see what they recommend for block detection.


----------



## fcwilt (Sep 27, 2013)

Hi,

A common type of block detection is sensing current flow in the block.

There are two common approaches to this. 

One uses the voltage drop across one or two diodes. With this approach you typically have to connect the block power wiring "through" the device to the block.

Another approach, that I favor, uses coils that you place over one of the power leads to each block.

The two small wires from the coil go back to the actual electronic sensing device which sends information to the computer.

One thing I like about this approach is that it totally separates the power wiring to the blocks from the wiring to the sensing devices, allowing you to optimize each type of wiring.


I also have a fully automated model railroad using TrainController software and RR-CirKits electronics.

Frederick


----------



## MichaelE (Mar 7, 2018)

Thank you for your reply. 

*One thing I like about this approach is that it totally separates the power wiring to the blocks from the wiring to the sensing devices, allowing you to optimize each type of wiring.*

Do the sensing devices _not_ rely on the current draw from the power wiring to the blocks? I may be mixing my apples and oranges. I would appreciate a separate fruit basket explanation. 

I think I sent a similar question to Viessmann and baffled them too. I got an e-mail forwarding it to one of their 'signal experts' and have still not heard back after two weeks.


----------



## fcwilt (Sep 27, 2013)

MichaelE said:


> Thank you for your reply.
> 
> Do the sensing devices _not_ rely on the current draw from the power wiring to the blocks? I may be mixing my apples and oranges. I would appreciate a separate fruit basket explanation.


Both approaches sense current flow to the block.

The diode based devices are connected between the DCC command station power (one lead only) and the block.

When current flows through the diodes a voltage drop is generated which the electronics in the device can sense.


The coils on the other simply require you to pass one of the power leads to the block THROUGH the center of the coil.

There is no actual electrical connection of any sort between the block power wiring and the electronics wiring the coils are connected to.

When current flows in the wire passing through the coil it induces a small voltage in the coil that can be sensed by the electronics.

Also coils do not introduce any voltage drop in the power to the blocks as do the diodes.

I had devices based on diodes until a friend put me on to RR-CirKits devices (which use coils).

I sold all of the stuff I had and went with RR-CirKits.

Great stuff.

Frederick


----------



## MichaelE (Mar 7, 2018)

Thanks!


----------



## sachsr1 (Mar 3, 2016)

If you plan on running multiple feeder wires to each block I would recommend using small terminal strips for each block. You can run all the feeder wires to the strip and then one wire back to the main bus wire. This is nice because if you add something like a NCE BD-20 sensor you just have to wrap the one wire through the sensor.


----------

