Amp usage of N scale locomotives

[n2mopac]

Please help out an electronics dummy. I am getting the Prodigy Advance DCC system for my new layout for Christmas (no surprise, but I'm very excited). I know it is rated at 3.5 amps but with the provided power supply only produces 2.5 amps. I intend to use one or two boosters and power districts to power my entire layout as I complete more of it. So here are my questions:

1) How many amps does a typical N scale locomotive pull? I plan to have (eventually) 12-15 locomotives on the layout at a time with a maximum of 8 of them running at any given time.

2) What would be the best booster (or any good booster) to use with this system as I expand?

3) I understand the basics of DCC wiring, but how does one wire these boosters into the system so they recive commands from the Prodigy Advance system and power their individual districts?

4) Is there a problem using the 2.5 amp power supply of Prodigy Advance and adding boosters of different amperages? I think I know the answer here--no, as long as they are electrically isolated--but I am looking for confirmation and advice.

Any and all help you can offer is greatly appreciated.

Thanks,
Ron

[rrinker]

1. 8-10 is a good guess, most newer N scale locos draw about .25amp running, higher stalled.

2. Anything with optoisolated inputs, MRC Power Station 8 or one of the Easy-DCC Booster5 or Booster10 units would work.

3. The input of the MRC Power Station 8 (I think that's what it's called) takes track power levels - so you would connect a pair of wires to the track outputs of the Prodigy booster and connect to the inputs of the PS8. The 8-amp output of the PS8 would go to your track. Put gaps in both rails between the sections fed by each booster. More importantly, check out Tony's Train Exchange and the PowerShield electronic circuit breakers. Especially in N scale, I would break the layout up into more than just 2 power districts, maybe about 5 or 6, depending on the size of the layout. One would get fed directly from the Prodigy booster, the others through the Tony's Power Shields set to a low trip current (plenty to run a bunch of N scale locos). The input to all the Power Shields would come from that MRC Power Station.

4. Nope. Amps doesn't matter. Voltage does - if there is a large enough differents in volatge from one booster to another, as your locos cross the gaps they will surge or slow down. More annoying than harmful, although too big a surge could put the train off the tracks. Look for an adjustable output voltage on the booster - I'm pretty sure the MRC PS8 has this. Watch the voltage - some brands of DCC systems think there's nothing wrong with putting 18v to the rails for all scales. 18v is too high for HO, and DEFINITELY too high for N.

--Randy

[n2mopac]

Thanks for the infor Randy. Let me see if I understand. Can I not connect the supplied 2.5 amp power supply to one district and use say a 5 amp power supply to power my other districts (6 total)? I thought from what I had read that I could do this and connect the two power supplies together through a command bus. I don't actually have the thing in hand as it is a Christmas gift. I won't have it to look at until the 25th.

Ron

[rrinker]

It really depends on the system as to how you interconnect extra boosters. I don't think there is a 'command bus' with the Prodigy Advanced which is why you have optoisolated booster inputs like the Power Station 8 which can connect directly to the track outputs of the initial command station/booster to get the signal. The draw on the minimal 2.5 amp output is minimal, so this can ALSO connect to track and provide power. However, if you don't use some sort of circuit breaker like the Tony's ones I mentioned, if you get a short in the section controlled by the original booster, the signal will be lost that also drives the second booster and those trains will also stop.
I will try to draw it: PA = original Prodigy Advance, CB = circuit breaker, PS = Power Station 8.

PA ==== PS === CB === track
||
||
more track

You CAN connect it directly, but you really should put circuit breakers in before the track and divide it up into power districts to that a derailment won't bring your entire railroad to a halt. Although, you didn't say how big your layout is. The Prodigy Advance is actually capable of 3.5 amps, they oonly supply a 2.5 amp transformer with it though. Check on Tony's Train Exchange, they offer an upgraded power supply so that you can use the PA's full 3.5 amp capacity. At approximately .25 amps per locomotive, that's 12-14 running at the same time. If that's all you need, upgrading to a bigger power supply is a lot cheaper than a whole new booster.

--Randy

[n2mopac]

That is very helpful. Thanks. I do plan to use circuit breakers like Tony's or Digitrax on my power districts. The layout will have 6 districts in all. Thanks again for the help.

Ron

[Wdlgln005]

check out the Product Review section of this website. The amp info you ask for should be a part of evert test. Take the Kato SD40 as an example, the table shows amps varying from .08 at startup to .90 at full throttle. You want to be sure to find the midpoint that usually represents the full speed of the prototype. Nscalers should never operate at full throttle, so you always operate at scale speeds.

[rrinker]

QUOTE: Originally posted by Wdlgln005

check out the Product Review section of this website. The amp info you ask for should be a part of evert test. Take the Kato SD40 as an example, the table shows amps varying from .08 at startup to .90 at full throttle. You want to be sure to find the midpoint that usually represents the full speed of the prototype. Nscalers should never operate at full throttle, so you always operate at scale speeds.

Yeah just watch out for faulty equipment [:D] It was about a year or so ago there was a series of 2-3 months when all the amp ratings were 1/10th of the actual values, MR corrected it once they discovered the error. Sounds like someone had the meter on the wrong scale. I got suspicious when the stalled current for an Atlas O scale dual-motored diesel was listed as .5 amps. [:D][:D]

--Randy

[beyerswede]

How does this look for an N Scale layout with say 10 locos at once


PA======P8==||
=======CB===Track
||
||=======CB===Track
||
||=======CB===Track

Thus, setting up sub busses within the limits of the 8 amp power station?

[n2mopac]

QUOTE: Originally posted by beyerswede

How does this look for an N Scale layout with say 10 locos at once


PA======P8==||
=======CB===Track
||
||=======CB===Track
||
||=======CB===Track

Thus, setting up sub busses within the limits of the 8 amp power station?

Thanks. This is truly helpful. I think I have a handle on it for now. I'll let you know more as I do the actual wiring.

Ron

[rrinker]

QUOTE: Originally posted by beyerswede

How does this look for an N Scale layout with say 10 locos at once


PA======P8==||
=======CB===Track
||
||=======CB===Track
||
||=======CB===Track

Thus, setting up sub busses within the limits of the 8 amp power station?

That comes out OK when I reply, but they didn't line up in the original message. What you drew there would work fine, except you are wasting the output of the Prodigy Advance base unit. I would tap off that line going from the PA to the P8 into another CB, and then to the track. A CB on that line is important if you do feed the PA output to the track, otherwise a short in that section would cut the feed to the P8 and stop everything.
If by some chance you use Tortoise switch motors powered by stationary decoders, that would be a great place to connect them, the 2.5a of the PA cna drive a LOT of them! Always through a CB though, you do not want an interruption in the line between the PA and the P8. If this isn;t clear, I will try making another drawing.

--Randy

[n2mopac]

QUOTE: Originally posted by rrinker

QUOTE: Originally posted by beyerswede

How does this look for an N Scale layout with say 10 locos at once


PA======P8==||
=======CB===Track
||
||=======CB===Track
||
||=======CB===Track

Thus, setting up sub busses within the limits of the 8 amp power station?

That comes out OK when I reply, but they didn't line up in the original message. What you drew there would work fine, except you are wasting the output of the Prodigy Advance base unit. I would tap off that line going from the PA to the P8 into another CB, and then to the track. A CB on that line is important if you do feed the PA output to the track, otherwise a short in that section would cut the feed to the P8 and stop everything.
If by some chance you use Tortoise switch motors powered by stationary decoders, that would be a great place to connect them, the 2.5a of the PA cna drive a LOT of them! Always through a CB though, you do not want an interruption in the line between the PA and the P8. If this isn;t clear, I will try making another drawing.

--Randy

That is clear as a bell. I do intend to run one track district from the PA and otherwise follow the suggestion of this diagram. Tony's makes a 4 line breaker system. That would allow for 4 districts on 80' of main, 300' of total track (yards and industries included) which I think will work well. Thanks again.

Ron