As I'm researching DCC systems, I can think of two reasons to choose a low amp (1.6-2.5) DCC system like the MRC Prodigy Express or Digitrax Zephyr ...
1) With low amps you may be able to get away with using your existing DC wiring (20-22 gauge) ... the voltage drop would be too high for a 3.5-5 amp system ... which would require say 16 gauge wiring ... is there any truth to this line of reasoning?
2) Lower amp systems are less likely to fry your decoders if something goes wrong. Is this true? You guys tell stories of frying lots of decoders.
So, how many amps does a loco (say a Bachmann HO Shay) running DCC without sound use? running with sound? idling with sound? Can you run 2 and idle 2 sound equiped loco with 1.6 or 2.5 amps?
Hopefully my questions aren't too crazy. I have been learning a lot about DCC in the past week, even if it doesn't seem so ...
Thanks,
Marty
www.oakhurstrailroad.com
"Oakhurst Railroad" on Facebook
You should be able to run two non-sound DCC engines that are mechanically well engineered and in good running order with less than one amp,..but it depends on the load the motor must pull. Grades, tight curves, heavy cars, stiff and gummed up truck journals....they all add up.
As soon as you add a substantial load, and/or sound, you add another 0.4 amps, give or take, per decoder.
If you are a lone operator running two or three consisted non-sound diesels, your total amperage draw might be near 1.5+ amps if they are pulling 30-40 cars on level track. In the final analysis, only a rampmeter will tell you for sure, but this would be a good start for consideration of current needs and then what your future needs might be.
-Crandell
With my Zephyr I was able to run the following:
2x PCM T-1 (loksound decoders), BLI M1A (QSI sound), BLI GG1 (Qsi sound), 2x P2K GP-7 (DH163L0 motor only decoders), P2K S-1 (Digitrax motor decoder), and a Stewart DS4-4-1000 (TCS T1 motor only decoder).
That was all I could manage to fit on my 8x12 layout and not have them crash into each other. Low amps? People tend to grossly overestimate the power required for locos, particualrly sound ones. Pay attention to the stall current ratings in MR reviews, even some of the sound locos draw no more than half an amp with the wheels forcibly restrained fro moving. This is the absolutely maximum current the loco will draw, under most conditions it will be drawing less.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Oakhurst Railroad Engineer 1) With low amps you may be able to get away with using your existing DC wiring (20-22 gauge) ... the voltage drop would be too high for a 3.5-5 amp system ... which would require say 16 gauge wiring ... is there any truth to this line of reasoning? 2) Lower amp systems are less likely to fry your decoders if something goes wrong. Is this true? You guys tell stories of frying lots of decoders.
Hey, guys, although you sort of answered his how much current does an engine draw question, I think what really needs to be addressed are the two things he states above.
Because I don't need a high amp rig. I can run everything I need with my Zephyr.
Dr. Frankendiesel aka Scott Running BearSpace Mouse for president!15 year veteran fire fighterCollector of Apple //e'sRunning Bear EnterprisesHistory Channel Club life member.beatus homo qui invenit sapientiam
maxman Oakhurst Railroad Engineer 1) With low amps you may be able to get away with using your existing DC wiring (20-22 gauge) ... the voltage drop would be too high for a 3.5-5 amp system ... which would require say 16 gauge wiring ... is there any truth to this line of reasoning? 2) Lower amp systems are less likely to fry your decoders if something goes wrong. Is this true? You guys tell stories of frying lots of decoders. Hey, guys, although you sort of answered his how much current does an engine draw question, I think what really needs to be addressed are the two things he states above.
You are right maxman. Always the risk of asking more than one question in an e-mail or post. This is great information on loco current draw that I will use ... but questions 1) & 2) are the main reason for the post.
Thanks again,
Question #1. Yes and no. You may get away with the smaller wires but a quarter test is the only way to tell. If the system does not have short protection than troubles are the same as larger systems.
Question #2. You can still fry a decoder with 1 amp. You can stop a heart with less than 1 amp. I have had decoders go poof on the program track. A short on a layout for example running a thrown switch against you will cause a short and the reason for a super fast booster trip will limit the damage to a decoder. Some times they just get scrambled and need a reset.
Question #3. My Power Cab with less than 2 amps had 5 sound equipped and 6 silent HO scale locos running at the same time. There is a built in Amp meter on it and it read 1.5 amps on that load. The big draw you realize is the lighting of your Passenger cars. They can rob some power.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
Marty,
22 gauge wiring is not good on DC either! The only place you should use #22 is on the feeders from the 'bus' up to the track(usually about 6"). My DC layout used 6" #22 feeder drops to a #18 bus from the control panel. Most layouts are wired with too small wire(even DC).
The reason DCC layouts are wired with larger bus wiring from the start is due to ALL of the current flow is on the main bus, not just 1 or two engines worth of current like on a DC cab block.
A small home layout using something like a Digitrax Zephyr or a NCE Powercab should have at least #18 bus wire. You can then run #22 feeders from the bus to the track(one for every piece of flex track).
As far as a lower amp system is safer - A 10 amp system or a 1.6 amp system will 'shut down' when it detects a short. With smaller wire(higher resistance) - it may take a while to get to the short, and your decoder is 'frying' while that happens. Use larger wire. The 'quarter test' should force an immediate booster shutdown from any point on the layout.
Most of the newer HO engines will draw about .25 amps running. I have had 6 engines running off of a 2.5 amp Zephyr - and 3 were sound. Once a sound engfine powers up, it really does not use much more current that a non-sound engine. Idling really is not a lot of power drain. Our club had something like 32 engines parked in the engine terminal and finally that tripped the power district limiter(PM42).
My layout has a Digitrax Chief(5 amps) and a booster(5 amps) - real overkill for a home layout. I currently have 16 engines on the rails. About 1/2 are 'sound' engines(Spectrum/BLI steam & P2K sound diesels. Add a few more P2K and Atlas non-sound diesels. If I were to get the 2.5 amp Zephyr I use upstairs for programming(I got a 'good deal' when a LHS closed), I am sure I would get a shut down at some point. Your question is can you run 2-3 Sound/DCC engines on a NCE Powercab or Digitrax Zephyr? Yes, that is no problem. Both are 'home layout' sized starter systems that can 'grow'.
I saw a home layout(5X10 with two 2X8 extensions down two walls) last year on a layout tour. It was built from the start with DCC in mind, and was wired with a #18 'bus' and #22 or #24 feeder drops. All of the engines were newer Sound/DCC engines, and the entire layout was powered by a single 2.5 amp Zephyr. The guy had a pair of 'radio' throttles. He had a train running on the main loop and one or two local/switch jobs that he and his son were running as he talked with the guests - Smooth running layout. He was moving out onto the mainline to spot cars as that mainline train moved slowly around the main loop. Now try that with DC cab control!
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
Oakhurst Railroad Engineer1) With low amps you may be able to get away with using your existing DC wiring (20-22 gauge) ... the voltage drop would be too high for a 3.5-5 amp system ... which would require say 16 gauge wiring ... is there any truth to this line of reasoning?
I don't think this line of reasoning holds much water, the current only gets drawn when you need it. Actually, the small wire is going to work against you. You will get more voltage drop, turn the throttle up, and need to draw more current to get the same performance. So the capacity of your system to provide the current you need will be reached even sooner than it would otherwise.
Oakhurst Railroad Engineer2) Lower amp systems are less likely to fry your decoders if something goes wrong. Is this true? You guys tell stories of frying lots of decoders.
Jeff But it's a dry heat!
Oakhurst Railroad EngineerAs I'm researching DCC systems, I can think of two reasons to choose a low amp (1.6-2.5) DCC system like the MRC Prodigy Express or Digitrax Zephyr
Can you run 2 and idle 2 sound equiped loco with 1.6 or 2.5 amps?
I don't think you would regret a Digitrax Zephyr or the Prodigy. I personally own a Zephyr (among others) and have been very pleased with it.
No truth to it whatsoever. Ohms law still applies. E=IxR The voltage drop will not change no matter how many amps are available at the booster end. Voltage drop will be a factor of the resistance in the wiring and components. Smaller wire running long distance (bus wires) mean more resistance.
What will be affected is the system's ability to detect a short circuit and cut power. Higher resistance will slow or completely fool your system's breaker. Good news is the wire under the layout may melt before the rolling stock is damaged. Which brings us to #2
Who told you two amps won't heat metal parts enough to cause damage? A tail light bulb uses two amps. I've seen those melt the plastic housings they are held in.
Not saying a low amp unit is not for you. Just saying these two reasons should not be part of the decision.
Martin Myers
Lower amp draw will result in lower loss through otherwise identical wiring - a 2.5 amp load will show half the drop through identical wiring as a 5 amp load.
But the key word - LOAD. It doesn;t matter if you have a 2.5 amp DCC system or a 10 amp system, the LOAD in a given section of track will be whatever the current draw of the loco running there is. Just because the DCC system can supply up to 10 amps doesn't mean it is PUSHING 10 amps intot he wires. It doesn't work that way.
Still, #22 wire is definitely too small to use a bus wires. As short feeder drops in HO and smaller scales, it is fine. If you never expect to expand and run more trains at a time, then you might be able to get away with using somethign smaller than #12 as the bus wires (unless it's a long run - here were are back at the size of the layout does not really determine the size of the DCC system - I could fill a 20x30 basement but if I never run more than a single loco at a time, I certainly do not need an 8 or 10 amp system. However, that's a lot of wire in the bus runs and even with heavy wire at low loads there's a significant voltage drop).
mfm37Who told you two amps won't heat metal parts enough to cause damage? A tail light bulb uses two amps. I've seen those melt the plastic housings they are held in.
Bulbs get hot because they have to. An 1157 has low but measurable resistance, so when the appropriate current flows the filament gets hot enough to release photons (the light). That being said, the general point is well taken, 2.5 amps at 15 volts (power output of a Zephyr) is equivalent to a 35 watt soldering iron, and those get above 400F.
Alan
Co-owner of the proposed CT River Valley RR (HO scale) http://home.comcast.net/~docinct/CTRiverValleyRR/
Doc in CT...An 1157 has low but measurable resistance...
Wouldn't that be, "a lot of measurable resistance?" The whole point of the filament is to provide so much resistance, but in a temperature capable metal, such that its temperature rises to the point of releasing much of its 'gray' body radiation in the visible spectrum, with the rest in IR.
(See "electrical characteristic" well down this wiki page: http://en.wikipedia.org/wiki/Incandescent_light_bulb )
Marty, here are my decoders that I used 22 gauge bus wire with.
Any more questions?
Cuda Ken
I hate Rust
UPDATE: Well, I bought a Digitrax Super Chief xtra 5 amp system. I tested it on my coffee table with a piece of flex track on a DC and DCC locomotive. Worked great. Then replaced one of my 3 DC powerpacks and slid all of the DC switches to let the DCC system power everything. Worked fine everywhere on the layout. I did the quarter test for shorts and that worked everywhere except at part of one long block. I added an extra feeder to the other end of the block and the quarter test now works everywhere on the layout. I had previously installed a pair of bus wires around the layout (small, but 2-level), but I am currently not using them.
Do you agree that if the quarter test works everywhere and operation is normal, that I do not need to wire to the bus?
I currently am using the existing DC reversing switch (DPDT from an Atlas Controller) for my single wye section. It works, but does short out the layout if you don't guess right in setting the directions. I have a Digitrax AR1 auto reversing unit that I will probably install after I get the majority of my locomotives converted to DCC.
Welcome to the DCC world. If the layout wiring passes the quarter test than I see no reason to rewire the layout. Probably a good idea to test every now and then down the road. It would be wise to disconnect the rest of the DC power packs from the track wiring. If you accidentally flip a switch and put DC on the rails it would turn your Super Chief to a super smoking chief. If you really need to keep the DC installed at least make it very hard to switch between DC and DCC. Even if the Chief is powered down I don't know what would happen if DC is back fed to the booster/command station. I would not want to find out.
1) With low amps you may be able to get away with using your existing DC wiring (20-22 gauge) ... the voltage drop would be too high for a 3.5-5 amp system ... which would require say 16 gauge wiring ... is there any truth to this line of reasoning? 2) Lower amp systems are less likely to fry your decoders if something goes wrong. Is this true? You guys tell stories of frying lots of decoders.
Marty -
rrinker is right on. Electrical current (amperes) is not the driving number; current will be drawn as required by the load (resistance, motor, lamp) at the driving voltage. The amperage rating is just the upper limit on the current that the system can supply and still maintain the rated voltage. Low current available, fewer engines can be driven.
A Zephyr is good for small applications only - like a 4x8 with one or two engines. Sure the ads say it can do more, mine gets confused and overloaded pretty easily. If that's the kind of layout you have, a Zeph will work for you. If you have several engines, you really need something huskier.
Decoders do not fry because of 'high-amp' systems - they fry because they have been hooked up incorrectly, or the track layout brings them into a dc-dcc bridge, or something like that. A Zeph will fry a decoder just as fast as any.
And yes, #22 wire is too small for much more than short runs (a few feet at most) - whether dc or dcc.
Dick Chaffer / Bozeman, MT
Dunno what you're running on your Zephyr - but I've had 8 HO locos running at once with no problems. 4 had sound decoders, 4 did not. I wanted to try more but it was getting tough to keep them going without hitting each other. I even tried shorting the track to see if it would recover and indeed it did. Even if I have 2 other operators besides myself, I wouldn't need a more powerful system.
ANd I'm not the only one who has managed more than 4-5 locos with a Zephyr. If things start slowing down or getting wierd I suspect you don't have suffcient wiring, eithe rnot enough feeders or too thin a wire used for the bus.
jrcBozeA Zephyr is good for small applications only - like a 4x8 with one or two engines. Sure the ads say it can do more, mine gets confused and overloaded pretty easily.
"A Zephyr is good for small applications only - like a 4x8 with one or two engines." Say what? Sorry, but that's totally incorrect.
Here's proof in the pictures of my 25' x 50' HO layout:
And here's a pic of my entire DCC control system for the entire layout:
That's it. There's a UR91 and a half dozen UP5's around and about, but that's the extent of my DCC system. One Zephyr and some 14AWG wire for my 200' long double track mainline. These pictures were taken 5 years ago, and the layout still runs just fine today.
When I have operation sessions, we have had up to 4 people running trains at the same time (no more than two locos per train for my sessions...usually), and that's for 2 hours. I have never had a major DCC problem with my layout.
Paul A. Cutler III
OK Paul I'm hiding your pictures because it ruins my justification for picking up a Super Empire Builder Xtra so I can use the DB150 as a booster to power the layout and the Zephyr's output to power my accessory decoders.