Power source for G Gauge layout


goscrewyourselves

I'm the one
Hey guys,

Question on power sources for a G Gauge layout of about 135' in length. Can any DC power source, such as an MRC, be used on a G Gauge layout or do I have to be a G Gauge specific one?

The only thing that I have read about power sources for G Gauge is that they should be capable of 5 amp for absolute reliability. Other than that, I can't seem to find a definitive answer to my question.

Personally, power is power so long as it is getting to track, so (in my opinion) I can't see what "type" or power source is used, so long as it is large enough, but that is just my uninformed, no knowledge, electrically brain dead opinion - which I am sure is 99% wrong for a lot of reasons :)
 
My G scale set, came with the same power pack/power supply as my N scale set ( the wallwart, controller setup).........So I guess that means "any power source" would work, but 135' is a long run in any scale, so I'd say your idea of 5 amps would be a safe bet. You'd probably be OK with half that if you're running a single loco and put in a lot of feeders. G scale locos are often run off battery packs similar to RC cars , so they aren't neccesarily hi-draw power wise.
 
Tony I have an MRC power pack that has a switch that goes from N to HO to G scale.
Can't say about the length of track but I'd think a power bus similar to an HO would be in order?
 
Thanks guys,

Dave, I will be running 1 engine with 4 or 5 cars behind it so from what you guys, as well as another, have said it sounds like any DC power source of at least 3 amp and 18 volts will do the job.

I can't recall who it was but someone said they ran a G Gauge with about 100' of track with only one connection to the track. Despite that, I will be having at least 2 feeders to the track, central to the longest runs and am thinking about putting in provision for an additional 2 feeders, one at either end. Basically running a power bus similar to a HO scale, as Rico said.
 
Can't say about the length of track but I'd think a power bus similar to an HO would be in order?
Remember this is brass track. It conducts electricity almost as well as a copper wire. The concept of a bus to get around the high resistance of HO and N scale nickel-silver track does not apply. I would guess a g-gauge brass rail is approximately equal to an 8 gauge bus. The issue and need for more feeders isn't the length of the rails but rather the number of track joints and potentially loose joiners.
 
My G scale set, came with the same power pack/power supply as my N scale set ( the wallwart, controller setup).........So I guess that means "any power source" would work, but 135' is a long run in any scale, so I'd say your idea of 5 amps would be a safe bet...

The length of track has no bearing on how much amperage you power source needs to be.
 
"...The issue and need for more feeders isn't the length of the rails but rather the number of track joints and potentially loose joiners...."

This layout will (as it is pictured in the Layout Forum) contain 58 sections of brand new LGB Brass track with joiners already in place. I haven't taken a close look at the track or joiners but, and I think Iron Horseman can confirm this, the joiners slide over the rails and each joiner has a "lip" that "locks beneath the track tie" holding it in place and, presumably, the two sections of track together. I will get the two sections I have out and have a close look tomorrow though.

So, assuming that all track sections are firmly connected and that the track is brass, having 2 power connections to the track should be sufficient then, in theory. However, that is going to depend on how well the track sections lock together and how well I do them. Sounds as though the best way to do this is the same as for any layout ... lay a length of track, attach power, test the connections and continuity of power to the track - if all is good, add more sections of track, test and repeat until the engine stops running then add a feeder to the section just before the engine stops.

How does that sound to you guys?

So another related question...the difference and job of an AMP compared to a VOLT? If that makes sense.

I understand that a particular engine needs X amount of power to run so does that engine get its "power" from the Amperage or the Voltage? I am guessing it is the voltage but have no idea why. If it is the voltage that provides the power for the engine to run, what is the function of the amps and why are they so important? Or am I way off base?
 
The power any electrical device uses is figured in Watts, which is a product of the amperage and the voltage (volts X amps = watts) So you can have a circuit that is 120 volts and one amp and another that's 12 volts at 10 amps and both would give you 120 watts of power. Working backwards a 40 watt household lightbulb at 120v uses 1/3 of an amp. You can think of the voltage as "pressure", which is why you can't just use any voltage you want...........if you put 500psi of air in your car tire that's designed for 35psi, you'll get a very load bang and a ruined tire.......if you put 120 volts to a circuit designed for 12, you get magic smoke and a ruined device. Amps is the actual flow of electrons.....Ohms law says I = V/R where R is the resistance. So in our case, R would be the resistance of the track and motor, which is constant. So when you turn up the dial on your power supply, the voltage goes up ,your resistance stays constant , and your amperage goes up . For example if your track and motor have 5 ohms of resistance , at 2 volts you would be using .4 amps (2/5=.4), but if the voltage goes to 10 volts you'd be using 2 amps. That answers at least part of your question.
 
So another related question...the difference and job of an AMP compared to a VOLT? If that makes sense.

I understand that a particular engine needs X amount of power to run so does that engine get its "power" from the Amperage or the Voltage? I am guessing it is the voltage but have no idea why. If it is the voltage that provides the power for the engine to run, what is the function of the amps and why are they so important?
Well, for our purposes, there cannot be one without the other. As Dave says, thinking of water in a garden hose is a good analogy. The Amperage is the actual water, while the voltage is the pressure behind it. So if the hose is like a wire one can imagine that the higher the pressure the more water will be pushed through (ie. more power). If too much pressure is applied the hose ruptures and no water flows. On the other hand if there only a few cups of water available in a system that needs gallons, all the pressure in the world is not going to push more than that few cups through. That is the amps. If there is only 1/2 amp of power available and if a loco needs 2 amps it is going to be current starved and have no power.

This analogy also works for the size of a wire. Anyone can hook a 1/2" hose and a 3/4" hose to a "Y" connector. Turn on the spigot so one knows the pressure (voltage) is the same, but a whole lot more water is going to come out of the 3/4" hose. Applying that to feeder size, a tiny 1/8" hose (a 24 gauge wire) cannot deliver enough water (amps) to the load without exceeding the max pressure (voltage) of the system.
 
I just remembered something else. A while back I remember someone buying brass track at a swap meet. Chatting with them for a while I found out that they were mounting it on the underside of their layout to use for their DCC bus. It was much cheaper than buying 14 gauge copper wire.
 
Gents,

Thanks for that - I now understand it a bit better, or at least can now relate to it and appreciate the relationship between the two. Now to see if I do have it a little understood ...

Because brass track has better conductivity and; therefore less resistance, it does not require as much voltage to achieve a higher amperage than, for example, nickel silver track and it is the amperage that is being supplied to the engine for that engine to run. So, the amount of amps required will depend on the amount of amps that an engine needs for it to run and that is controlled by the voltage.

So, if an engine needs 2 amps to run, and I am using brass track then I may (for example) only need 12 volts to generate that amperage, where as if it were using nickel silver track, I may need 15 volts to achieve the same amperage.

That being the case (hopefully) I really need a power supply/transformer that has an adjustable voltage so as not to generate too much amperage.
 
...So in our case, R would be the resistance of the track and motor, which is constant...

The resistance of the track is not constant, it will vary depending on how much track is between the engine and the power source.

...So, if an engine needs 2 amps to run, and I am using brass track then I may (for example) only need 12 volts to generate that amperage, where as if it were using nickel silver track, I may need 15 volts to achieve the same amperage...

While you can increase your supply voltage to compensate for voltage drop in the track, that's not a good solution. The voltage drop is going to vary depending on how far the engine is from the voltage source. If you have a lot of voltage drop at the farthest point and you just increase the supply voltage, as the engine gets closer to the voltage source it will speed up. Likewise, if you have it running at an acceptable speed close to the voltage source, it will slow down an possibly even stall as it gets farther away. That's one reason why you want to minimize your voltage drop. You cannot completely eliminate voltage drop, so there will be some variation in the engines speed at different points on the track, but you want to minimize this as much as possible and not just rely on increasing the supply voltage.

...That being the case (hopefully) I really need a power supply/transformer that has an adjustable voltage so as not to generate too much amperage.

Well, your going to need that anyway to be able to control the engine's speed.
 
That being the case (hopefully) I really need a power supply/transformer that has an adjustable voltage so as not to generate too much amperage.
That is exactly what a model train DC power pack does. It supplies a variable voltage to the track. But you are over thinking the amperage part. One can supply all the amperage in the world and the load (the motor in this case) will consume only what it needs.
 



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