# How Many Transponding Zones?



## jbooker (Jan 15, 2008)

Hi There,

Hoping Bob Grosh will come across this and help me out a little. I have lots of questions, but I'll start with the power bus as we're gearing up to bury some cable before the ground freezes.

I like this post in the archives:
http://archive.mylargescale.com/forum/topic.asp?TOPIC_ID=27487

In the spirt of what was said there, I'll include the following in my post too:

"WARNING ADVANCED TOPIC" the following information is not needed for the enjoyment of running trains.

The article helped me to know it's possible to wire up a computer controlled layout with transponding and not use block detection. Now I just need some advice as to how many zones I should use on my layout. We plan for about 900 feet of mainline, one (maybe two) reversing loops and another 500 feet of yard and sidings. The whole foot print is about 250' by 50'.

I'd like some advice as to how many power disctricts and transponding zones we should use. 

I'm guessing from the only information I can find on outdoor transponding (Bob's thread above) that we'd benefit from 3 to 4 districts of 3 zones each, but what do you think? I want to use software and transponding together (without detection wiring) to calculate direction and position acurately as in the 'Advanced Topic archive post'

I'd like to place the power supply, station, boosters and BDLs in the shed. Is that too far away?

Thanks in advance,
Josh

Below is a drawing of our layout with dimensions.

The track measurements are from centerline of the layout as follows.

Beginning at 12 o’clock:

Center to Trestle is 75 ft
Trestle is 41 ft
From Trestle around Loop to Center is 200 ft
Center to Tunnel is 150 ft
Tunnel is 14 ft
From tunnel around loop back to tunnel is 170 ft
Tunnel to Center (point of beginning) is 150 ft

Length of yard is about 75 ft


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## rwbrashear (Jan 5, 2008)

Hi Josh-

A few questions you should be asking yourself when determining power districts, automation layout, etc.:
1. How many trains do you want to run at one time?
2. What will be a typical consist? How many locos per consist? Which manufacturer's locos will you use? Are you running passenger traffic? If so, do you know the lighting load for each passenger coach?
3. Do you have an automation plan? In other words, ask yourself how you would like the layout to operate. (Or will you run the layout manually, using transponding for signalling?)

Questions #1 and #2 will help you determine the power requirements for your layout. If other words, will you need 8A, 10A or 15A boosters? 

Also note, the reversing loop and its adjacent tracks should be fed from the same booster. 

The transformers, command stations and boosters can remain in the shed. You will need to run large cross section power feeders to the layout. Landscaping wire is a good alternative. It comes in 10/12 AWG sizes. It's stranded and has a UV-rated jacket. It's also cheap and readily available.

I am sure Bob Grosh can provide answers to your transponding questions.

Best regards,
Bob


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## jbooker (Jan 15, 2008)

Thanks for your reply Bob.


We want to start with 3 or 4 trains. Mostly A-B-A's for freight and some passenger. So maybe 10 or 12 USA and Aristo locos max at a time. I want it to be controlled by user with transponding for helper functions like throw the next switch ahead and collision avoidance.

At this point I want to make sure I get the bus wiring done right so I don't have to dig too much stuff up over and over.

Josh


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## rwbrashear (Jan 5, 2008)

Josh- 

I'd start with at least four, 10A power districts. To be honest, three 15A Heller boosters would be a better alternative for USA Trains ABA passenger consists. These locos and passenger coaches drawn significant amounts of current. You could find a single passenger consist pulling 6A - 7A. While two trains will be over the 10A limit, they will be under the 15A Heller maximum. (Greg Elmassian can provide information regarding current draw for a single USA passenger consist.) You would have to source the Heller units from Germany. 

Here is a sample power calculation for an LGB F7ABA passenger consist. (The USA Trains locos will pull more current than their equivalent LGB counterparts.) 
http://1stclass.mylargescale.com/rwbrashear/DCC/Districts.pdf 

Remember, you can always start by pulling wire for additional districts. Compared to the cost and hassle of re-trenching, wire is relatively cheap. If you don't start with four boosters, pull the extra wire and isolate the four districts, but wire mutliple districts to a single booster. If you find you have insufficient power, isolate the feeders and add another booster. 

For the four 10A booster option, I'd recommend the following power districts: 
1. Reversing loop and eastern portion of the layout (Remember, the electrical length of the train must be in a single power district when using a reversing loop.) If this is a low traffic area, you can probably use an 8A central station for this district. 
2. Western portion of the layout (Long track sections will probably accommodate multiple consists.) 
3. North tracks of station and a section of the western loop (Parked passenger trains with lighted coaches and shunting operations will drain power.) 
4. South tracks of station and a section of the eastern loop (Parked passenger trains with lighted coaches and shunting operations will drain power.) 

If you run three 15A boosters, you can probably run the entire station from a single 15A district. 

If you are powering turnouts from DCC, use turnouts with separate power and signal inputs. Pull an 18VAC feeder for switches, lights, accessories, etc. 

Best regards, 
Bob


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## Greg Elmassian (Jan 3, 2008)

Need to measure the longer cars, 63' USAT RPO car has 11 bulbs inside, almost exactly 1/2 amp at 18v. I'm guessing the 80 foot cars are about .7 amps, so reasonable passenger train will draw more current than one loco. 

Will measure rest of them soon. 

Regards, Greg


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