DCC power requirements

[Anonymous]

Greetings all

I am wondering now about boosters.
I have the Digitrax zephyr w/ a DT400 throttle.
When I was asked how many locos I would run at one time I answered "ten". Well at the time I really had no idea. To be honest 3 would be the most I would run but that doesnt count for MU's and decoders for any other items I might need DCC to control.
Now that I have run my full length bus wire for around 400 feet of track I have noticed a drop in speed on my locomotives so I am guessing that like DC that the closer to the end of the line you get the weaker the signal. I was caught up in the whole "two wires is all you need party" And didn't think about signal loss nor did the salesperson at the LHS. Now after much thought and debate how many boosters would be good for a layout that nearly fills a two car garage with as many as 40-50 locomotives addresses stored and stationary decoders as well? How many boosters is overkill?
I am thinking of picking up two digitrax DB200's
to cover for the amps needed.
I welcome all thoughts and comments

thanks

[SteelMonsters]

It sounds like your problem isn't the amperage, but the in the wiring.

A bus of 14 gauge copper wire or larger will provide very low voltage drop. Feeders of 22 gauge or larger will enable to power the track and not burn out the wires. They should be short (12 inches or less but better off to have them 6 inches or less) and consistant in length to provide equal voltage drop. Also It's best to feed each piece of track or on a 6 foot interval and solder rail current carring jointers as rail has a high resistance compared to copper wire.


Boosters have internal voltage regulation. It should stay constant. If it does drop under load, then the power suppling the booster has inadaquate current rating. If you draw too much current from the booster, it will trip and cut power.

To dertermine what is adaquate current for your layout, think about how many trains will run on your layout maximum and how much current they will draw while slipping. Running 2 or 3 locos instead of 1 increases current but won't double or triple it. Also add in the current needed for stationary decoders and anything else drawing current. If your over the current, you can simply cut the bus and rails and have a booster for each half or one for each third and what not.

For heavy use layouts that get operated by many people, the best option is power districts. Isolate blocks which can be used for block detection for signaling, Heavy use areas get their own booster, more blocks per booster can be used for lower use areas. This also can be used with circuit-breakers. Circuit breaker's advantage is more safety as they shut down with less current which is usually adjustable, and they lower the disruption during short circuits. Basically you plut a single booster into it and get 2 3 or 4 lower current districts with a max of the booster's current. Can also be used to safely distict a large booster of 8 or 10 amps for smaller scale.

[cacole]

I concur with SteelMonsters' comments -- your problem is that you used too small a gauge of wire for your buss, and you possibly also need more power feeds to the track. That will be a lot cheaper than adding boosters. For a large layout, it would be advisable to have power feeds at least every 6 feet, or preferably every 3 feet.

I have ran nine Proto 2000 GP9s as a single consist from a 3 Amp booster with no loss of power, no matter how far away from the booster they were.

[rrinker]

Definitely sound slike too small a bus wire. Also, if at all possible, locate the booster in the MIDDLE of the bus, with approximately equal lengths on either side, minimizing the length.
You say you have 400 feet of track - since this is not entirely linear, I assume you don't have 400 feet of bus wire - or do you? Even #12 wire will have a significant voltage drop over 400 feet. The only way to fix that would indeed be multiple boosters, each powering a (relatively) short section of track. I will eventually be in a similar situation, around the walls my layout will extend for over 100 feet. I MIGHT get away with a single, centrally mounted booster with 50-60 feet of bus wire extending from each side, but I probably will use 2 boosters instead.
As for loco capacity - Digitrax doesn't 'store' anything except operating locos. So you could have 1000 decoder equipped locos, so long as you never run more than 10 at a time, the Zephyr will work fine, as long as you aren't exceeeding the power capacity, and that depends on the locos themselves.
A DB200 is a good idea for extra boosters. However, I would NOT connect them directly to the track, I would divide that up into power districts using something like the Tony's PowerShield.

--Randy

[Anonymous]

Ok so I mispoke when I said I had a power drop off
my bus wire is 14 gauge and I have feeders every 3 feet
so my little zephyr will handle anything I throw at it?

[rrinker]

I'm not sure I understand what you are trying to say then. If your locos slow down at the farthest point along the bus wire, you have a voltage dropoff problem. If your bus is 400' long, then switching to even #10 wire won't really fix that - but there are better ways to runt he bus wire that might reduce the length. If your layout fits in a 2-car garage, I'm sure the bus doesn't have to be 400' just because you have 400' of track.
You mention stationary decoders as well as the loco decoders - if you have all your switches controlled with stationary decoders, plus running 3+ locos, the Zephyr is going to run out of juice. Adding boosters, AND distributing them along the track bus, rather than cluster them all in one spot, will help with both problems - power and voltage drop.

--Randy