Surfstud31 wrote: jbinkley, what I meant was that as a sole operator it will be much easier for me to diagnose an electrical problem - blocks or no blocks. Without other operators on the layout, then I must be the problem. Incidentally, you don't find 10 blocks overkill on a 12'x13' layout? I'm curious because I am almost to the wiring stage and am trying to figure out how many blocks to do. I'm starting another thread on blocks and boosters to see what others do.
jbinkley, what I meant was that as a sole operator it will be much easier for me to diagnose an electrical problem - blocks or no blocks. Without other operators on the layout, then I must be the problem.
Incidentally, you don't find 10 blocks overkill on a 12'x13' layout? I'm curious because I am almost to the wiring stage and am trying to figure out how many blocks to do. I'm starting another thread on blocks and boosters to see what others do.
No, not at all. In fact I find it makes things easier, other than making sure you keep the polarity right between blocks. Having the blocks gives me lots of flexibility as to how I distribute power from the boosters to through the electronic breakers ultimately to the track. If I had one big block and exceeded the output of a booster, I'd have to figure out where to cut rails, insulate them, run new feeds and then wire them to the booster. Now to add a booster I just pick which breakers the new booster is going to power and then move the feed to the new booster. When I went to DCC and added sound locomotives, I ran the risk real quick of exceeding the capacity of a 5A booster.
If I get a short, the breaker indicator lights, I can flip the toggle switch to the block and fix the issue. I also have one block as a programming block so I flip the switch to program DCC locos in that block. Also if I ever want to add occupancy detection it is much easier when the blocks are already laid out. Lastly, having blocks makes it easy to install an autoreverse section (which I have a large section).
Just my 2 cents worth <g>...
Engineer Jeff NS Nut Visit my layout at: http://www.thebinks.com/trains/
nfmisso wrote: Surfstud31 wrote: The reason I am wondering all this is because I do have a readily available supply of 18 gauge wire. I'm thinking I might give it a try and if I have problems, then just replace the 18 gauge with 16 gauge or 14 gauge. Does this seem to be a stupid idea and a waste of time? Be honest, you won't hurt my feelings and may save me a lot of trouble. You could just double on the 18 guage, which is effectively 15 guage, or triple for about 13½, or quadruple for 12 guage.
Surfstud31 wrote: The reason I am wondering all this is because I do have a readily available supply of 18 gauge wire. I'm thinking I might give it a try and if I have problems, then just replace the 18 gauge with 16 gauge or 14 gauge. Does this seem to be a stupid idea and a waste of time? Be honest, you won't hurt my feelings and may save me a lot of trouble.
The reason I am wondering all this is because I do have a readily available supply of 18 gauge wire. I'm thinking I might give it a try and if I have problems, then just replace the 18 gauge with 16 gauge or 14 gauge. Does this seem to be a stupid idea and a waste of time? Be honest, you won't hurt my feelings and may save me a lot of trouble.
You could just double on the 18 guage, which is effectively 15 guage, or triple for about 13½, or quadruple for 12 guage.
That's true. But where are the faults in wiring likely to occur? Do you want to double, triple, or quadruple the number of connections you have. In my opinion, you only get one chance to do this the first time, and it makes sense to me to do the best you can now, and avoid as much possible trouble down the road as you can. You know Murphy is going to visit, why give him extra places to stay?
Jeff But it's a dry heat!
Brunton wrote: I'll have several long and several short buss wire runs (I only have one long run now), so I'll just use 12 gauge stranded for all of them, and not change to a smaller gauge for the short ones. I bought a couple of spools of 12 gauge wire from Home Despot (one red and one green) and just use them. Feeders are generally 22-gauge telephone wire. Where I need a relatively short sub-buss, I use thermostat wire (that's either 18 or 20 gauge). Seems to work fine so far... I also drop feeders only every 12 feet or so (thought I'd mention that just to stir up the "every three feet" guys!)
I'll have several long and several short buss wire runs (I only have one long run now), so I'll just use 12 gauge stranded for all of them, and not change to a smaller gauge for the short ones. I bought a couple of spools of 12 gauge wire from Home Despot (one red and one green) and just use them. Feeders are generally 22-gauge telephone wire. Where I need a relatively short sub-buss, I use thermostat wire (that's either 18 or 20 gauge). Seems to work fine so far...
I also drop feeders only every 12 feet or so (thought I'd mention that just to stir up the "every three feet" guys!)
Mark, I am in full agreement. I feel that many of us learn adaptive measures when we really don't understand the nature of our problems in the first place. We try something and it seems to fix our problem, so that must be the practice from now on in all instances. Bull.
I have run 23 feet of main with just two feeders, and had zero problems with my several QSI-equipped locos drawing the power I demanded of them. No magic smoke, so time-outs, no controller or decoder resets, nothing. I can't say I ever stacked long consists behind any of them, but I am quite confident that any subsequent limitations would have been more due to my trackwork and grades.
Mark P.
Website: http://www.thecbandqinwyoming.comVideos: https://www.youtube.com/user/mabrunton
Surfstud31 wrote: I understand the block concept and and was considering two blocks for my layout. I am a sole operator right now so I am not sure if it's necessary. Regardless, I will need at least 10' wire runs. This EE was trying to explain an example of a motor overheating (or running hot) because of not enough power going over wires that were too large. When the amps were increased to the motor, problem solved. I don't get it but then I'm not an EE.
I understand the block concept and and was considering two blocks for my layout. I am a sole operator right now so I am not sure if it's necessary. Regardless, I will need at least 10' wire runs.
This EE was trying to explain an example of a motor overheating (or running hot) because of not enough power going over wires that were too large. When the amps were increased to the motor, problem solved. I don't get it but then I'm not an EE.
Blocks have nothing to do with how many operators you have, they help with fault isolation (i.e. one short circuit and you lose the entire layout with a single block system) and they help with the ease to expand later (i.e. you need to add boosters). My layout is 12' x 13' and I have 10 blocks. Right now I use 3 boosters. I could easily go up to 10 without any rewiring.
Nice pictures of your layout.
I must have misunderstood him Dick because it didn't make sense to me and although I'm not an EE, I thought I understood enough about electricity to know that! LOL!
Oh, Jeff, here's a link to the thread for my layout progress pics:
http://www.trains.com/trccs/forums/946203/ShowPost.aspx
Surfstud31 wrote:jbinkley, what you said about the mechanical problems resulting from larger wire is what another EE was trying to tell me. Basically, from what I could tell he was saying, you can actually cause damage to an engine (motor) by using wire that is too big. I am not an EE and I have no idea why that is but I was concerned about it. I don't mind using 14 gauge wire as long as I know it will not cause the mechanical problems you and this other EE alluded to.
I wasn't referring to that type of mechanical problem. I don't see the point he is making. What I was referring to was having wire that is too big to work with effectively. At some point you need bigger terminal strips, the wire is harder to bend, bigger holes, etc.etc. The other point I was making was that if you break your layout up into blocks then your busses get shorter and thus the wire size requirements may be different. I even put blocks on my main line. Right now I use two boosters to power it but I could use as many boosters as I have blocks. This allows me to easily scale it as the current requirements increase. So, as an example, I could use 4 - 5A boosters and spread 20 amps over the 4 blocks. The wire size requirements for a 5A block would be much less than a single 20A block that stretched over the entire layout.
I hope this helps explain my point.
In general terms I (also an EE) disagree that using too large a wire can be as bad as too small (in this case), unless you go absurd. Also, it is important to know what the purpose of that table was, since the voltage drop through the wire is what is important, and the table doesn't tell you what the criteria were for determining the max length. Anyway, here is a little calculation: 12V, 5A, 18 gauge wire 1.3 Ohms per 100 feet, 16 gauge .818 Ohms/100ft, 14 gauge .516 Ohms/100ft. A 25 foot bus has 50 feet of wire (it also comes back, and the voltage drop is the same). We are ignoring the help the track MAY give here, but gaps or bad connections reduce that, so we'll be safe. So for 18 gauge wire you lose 5A x 1.3Ohms / 2 = 3.25 Volts in the wire, leaving less than 9 at the loco. 16 gauge: loses about 2 Volts, 14 guage loses about 1.25. These are worst case, five Amps draw at the extreme end, etc., so it probably is never that bad. But it shows that 18 is almost certainly a bad idea, 16 might be ok, 14 is a good idea, and if you are going longer you might want even more. There is no question that this is overkill, to an expent, and I'm not looking to argue that, but the extra expense and difficulty in going to 14 gauge isn't much to ensure you don't have a problem later, when there are more sound locos, etc., and things we haven't even though of yet hanging on decoders in the tracks.
In general terms I (also an EE) disagree that using too large a wire can be as bad as too small (in this case), unless you go absurd. Also, it is important to know what the purpose of that table was, since the voltage drop through the wire is what is important, and the table doesn't tell you what the criteria were for determining the max length.
Anyway, here is a little calculation:
12V, 5A, 18 gauge wire 1.3 Ohms per 100 feet, 16 gauge .818 Ohms/100ft, 14 gauge .516 Ohms/100ft.
A 25 foot bus has 50 feet of wire (it also comes back, and the voltage drop is the same). We are ignoring the help the track MAY give here, but gaps or bad connections reduce that, so we'll be safe.
So for 18 gauge wire you lose 5A x 1.3Ohms / 2 = 3.25 Volts in the wire, leaving less than 9 at the loco. 16 gauge: loses about 2 Volts, 14 guage loses about 1.25.
These are worst case, five Amps draw at the extreme end, etc., so it probably is never that bad. But it shows that 18 is almost certainly a bad idea, 16 might be ok, 14 is a good idea, and if you are going longer you might want even more.
There is no question that this is overkill, to an expent, and I'm not looking to argue that, but the extra expense and difficulty in going to 14 gauge isn't much to ensure you don't have a problem later, when there are more sound locos, etc., and things we haven't even though of yet hanging on decoders in the tracks.
Ok, so one EE to another, just to confuse folks here, let's talk about the concept of losing voltage in a real world situation. While I will agree with your calculations, when we are dealing with DCC the actual differential component of the bipolar pulses don't dictate the actual voltage driven to the motor at any given time. That is determined by the throttle setting. What a voltage loss would do is limit the maximum voltage being able to be delivered under load, which would ultimately impact the top speed of the locomotive, not a speed less than maximum. I don't know about you but I don't run mine at top speed. So as a locomotive moves further away from the DCC source (as measured in the feet of wire) you won't see a sudden slowdown because the wire resistance goes from .05 ohms to say .1 ohms. Also since a given locomotive won't draw 5A, the actual draw will be spread along the bus and determined by the amperage draw of the various locomotives based upon their distance from the source. Lastly, since we are dealing with differential voltage pulses, the DC component of this is not a constant as with standard DC and so the actual voltage drop as a function of the DC component and not a straight linear function. Sound locomotives have capacitors in them and smooth some of this out.
So what am I trying to say here ? I agree that a larger wire won't cause electrical issues but can cause mechanical issues. I agree that in general bigger is better but I don't believe it is as critical as some indicate. Also there are ways to use smaller wire by using multiple buses. I will often put a barrier strip in the middle of an area and run 3' 18 ga. feeders back to it. This is actually as effective as a 14 ga bus run along the track with smaller gauge feeders. So while I feel that proper wiring is important, it isn't catastrophic and things that are more important are blocks, which provide fault isolation and an easy way to add additional boosters in the future without cutting rail. Let's don't get too hung up on wire sizes and miss out on other important wiring items.
This is almost akin to the power routing vs not for switches. To me that is another of the less filling / tastes great debates...
Another argument for the larger wire. I have read of the quarter test, if the booster doesn't shut down when you put a quarter across the track you need a larger bus wire or another feeder.
I think the star would be fine, a four foot 'sub-bus' shouldn't cause trouble as long as it is 18 gauge or so, I'd think.
I agree, the other part of this is that a one way run of 10, 25 or 50’ is actually doubled in regards to voltage drop. If using DC one side will be greater due to the block switches.
Jim
I'd use 14, there's no compelling reason not to.
You can use the 18 for anything else, as long as it isn't you bus wire.
OK guys - you've convinced me. I will be running alot of sound locos (in fact so far ALL my DCC locos are sound), looking forward to DCC uncoupling someday, and those new MTH locos which just eat the power. These future power needs and your much heeded advice have convinced me to upgrade to 16 or 14 gauge for the main DCC bus. Now, is 14 or 16 gauge better for the main DCC bus with a max length of 25' (one way)?
Also, I assume I can use all that 18 gauge wire I have for AC accessories like internal building lights?
Soo Line fan wrote: I meant a total run of 25' (12.5 out and back) so both of our calculations are correct. Sorry for any confusion. Jim
I meant a total run of 25' (12.5 out and back) so both of our calculations are correct. Sorry for any confusion.
It's ok, I just wanted to make sure I hadn't messed up, I think there is enough misinformation floating around that it is good to be accurate when we can, and I wanted to fix it if I'd goofed. The best part is that your number pointed out that 18 gauge isn't even really enough at 12.5 feet! I'm sure there are lots or cases where it works, because of all of the things that are usually not worst case, and all of the helpful unknowns, but that's luck, not engineering.
Surfstud31 wrote: My understanding is that most DCC systems use 12V 0-5 amps - is this correct?
My understanding is that most DCC systems use 12V 0-5 amps - is this correct?
Here is what I'd say. IF you use the 18 gauge it will probably work, probably fine, probably forever. BUT. When it doesn't three years from now when you add a nice noisy sound consist, or extend the layout, or a gap develops in the rail that isn't there now, and things get squirrely, but just now and then, and you really can't figure it out, are you going to remember that you 'cheated' and used potentially inadequate wire? I'm guessing not. You can do it if you want, and you'll probably be ok, but.....I wouldn't. It is up to you, of course.
Soo Line Fan, did you remember that you have 25 feet out and another 25 feet back? I think it is actually twice what you said (unless I slipped up in my head, which is possible), and still your point is valid. Why cheat in the basics? Just like you said.
The voltage drop for a 2-wire, 25’ run using 18ga will be 1.646 volts. Now if your power supply is for example, a 12 volts you would only have 10.354v available to the trains. A loss of over 13%! Take into consideration other factors such as rail joiners and connections and it is conceivable that you will loose or “drop” 2 volts. If that is acceptable to you then that is fine. To me I would want all the power I paid for.
Lets use the same example, this time with 14ga wire. The drop will still be .648 volts. What I am saying is that even thought the circuit has the ability to provide enough current, your power supply will not have the ability to overcome the loss using small wire. Wire is so inexpensive in the scheme of building a model railroad it is the last place you want to economize.
Here is a link with voltage drop calculator. http://www.powerstream.com Select “Technical Resources” then select “Wire and Current Capability Chart.