Blocks in DCC

[Anonymous]

Hi are blocks needed for dcc or can you go with out them.

[jrbernier]

On a small layout, you can get by with no blocks. But on larger layouts 'Power Districts' are a good idea. I have 10 blocks wired through 4 'Power Districts'. If I have a short in one of the power districts, it does not shut down the entire railroad. With the layout seperated into the 10 'blocks', it is easy to trouble shoot an electrical problem. Each block has a 'bus' feeder that runs back to the DCC system.

Jim

[Anonymous]

If you are using signaling system, you need blocks.

[Anonymous]

I just have a small 4 x 8 layout in n scale. The old dc plan in a atlas book called for 12 blocks but i was wondering how many i would need because of using DCC.

Alan

[tomikawaTT]

This is 'you need 'em, but you don't.'

Build the layout blocked for DC with insulating rail joiners, then connect all of the N rails to one leg of your DCC bus and all the S rails to the other. That way, if you decide to go to track detection for working signals, your wiring is already in place. Also, if you develop a mystery short, it is much easier to find if you can disconnect sections rather than try to examine the whole layout.

[jfugate]

In a perfect world, you don't need blocks with DCC unless you are doing signalling.

However, for short management purposes, blocks are a good idea.

For any layout where you plan to run more than two trains at a time, breaking the layout up into at least two blocks (called power districts in DCC terminology), and attaching a booster to each power district is a good idea.

Each power district is electrically its own "circuit" and this helps to isolate any shorts to just that power district.

If you want the ultimate in short management, you should also subdivide the power districts into blocks and put some sort of short "catching" device on the sub-block feeders. You can use Tony's Power Shield at $30 each, or you can use 1156 auto tail light bulbs to do "poor man's short catching" for $1 each.

Here's a video demoing how the 1156 bulbs do their thing to help manage shorts on a DCC layout: http://mymemoirs.net/preview.php

[Anonymous]

Are both rails gapped in a block? I plan on using both power districts and blocks with the hope of adding signals in the future as well as for short management now.

I now have one power district, in the future this will be split into four. I know the rails are double gapped at the limits of a given power district, if I understand everything I have read, only one rail is gapped for a block. That rail is the rail the sub bus is wired to and in my case an 1156 tail light. If there is a short in any of the sub blocks, does that still shut down the parent power district, or does the light take the load, keeping the district up and running?

Thanks in advance

Mike in Tulsa
BNSF Cherokee Sub

[selector]

Yes, both rails.

[rrinker]

For power districts, both rails must be gapped. Common rail is not recommended for DCC. But for blocks used only for detection, usually only 1 rail needs to be gapped, depending on the detector being used.

--Randy

[CNJ831]

QUOTE: Originally posted by jfugate
If you want the ultimate in short management, you should also subdivide the power districts into blocks and put some sort of short "catching" device on the sub-block feeders. You can use Tony's Power Shield at $30 each, or you can use 1156 auto tail light bulbs to do "poor man's short catching" for $1 each.

I'm glad to see someone like Joe (and one or two others) bring up this important point. Too many hobbyists new to DCC think all that's necessary is to tie in two wires to a layout and everything is Jake. Then they get a short somewhere and go nuts trying to isolate the area in which it's occurring...while the entire layout is down!

CNJ831

[jfugate]

I cut gaps in both rails on all power district boundaries, and I also gap both rails in the train sub-blocks, but electrically, only the rail with the 1156 bulb protection needs to be gapped.

The beauty of the "short catching" of the 1156 bulb or Tony's Power Shield protection is when you get a short in a sub block, the power district stays up because the "short catcher" becomes the load in the circuit, preventing the short from getting back to the booster.

By definition, a short is a direct connection of one rail to the other without an intermediate load. The 1156 bulb, when cold, passes current with almost no resistance. But once the current flow jumps as it does with a short, the bulb suddenly lights up and becomes a resistor that causes a 2 amp load.

Since your average HO loco draws about 0.2 amps under normal load when not slipping, it's as if you suddenly put 10 locos on the track to the power booster. Obviously if the booster can supply more than 2 amps, and the current draw of the rest of the trains in the power district doesn't exceed the amp rating of your booster (minus 2 amps), then you are fine.

The sudden surge of current to the bulb can cause other trains in the power district to slow slightly, but they generally won't stop -- and that's the nicest thing about this short protection.

Before I added this short protection to my Siskiyou Line layout, all my operators were painfully aware of where all my booster boundaries were because any time someone would short something, the entire booster district would go down.

I installed the 1156 bulbs in 2000 and I doubt any of my operators remember where the booster boundaries are since now-a-days only the guy with the short has his train stop. Everyone else keeps running. [swg]