What happens with too much power on track?

[Blue Flamer]

selector

I am happy you asked!

If you wire a 2.4 amp 12 volt tail-light bulb in series, it will become the limiting device for current flow/usage in the event of a short.

In my case, I have four benches arranged in a square with a central operating pit.  Each bench is fed via a sub-bus, off of which come the feeders...not directly off my main bus.  So, off the bus must come two robust wires that T into a sub pair of wires that serve the module or bench component.  The rails are gapped so that this works....each bench gets one sub feeding it via feeder wires coming off the sub and up to the rails.

The twin wire bridge from the main to the sub gets a tail-light bulb soldered into one of the two wires...matters not which one.  I simply cut one of them halfway up, and soldered one end to the nub at the base of the bulb and the other to the scored and roughened chromed sidewall of the bulb body (solder wouldn't stick to the shiny chrome otherwise...believe me, I tried).

Now, when a metal tire on the engine bridges two rails, say during a derailment at a turnout, instead of the short detection circuitry noticing and then shutting down track power, the light immediately begins to draw the current and quickly gets to glowing brightly.  This prevents the circuitry back at my base station from tripping, thus shutting down all those sound decoders around the layout, but it also pinpoints the short for me.  Look to where the bulb is glowing, and there is where the short lies.

Where the metal tire is shorting, there is the path of least resistance around the layout, and to that place is where all the electrons quickly and preferentially flow.  Except, they run through the light filament, and the rest is obvious.

It is a cheap and highly effective shorts management set-up.  Not my idea, incidentally...has been around for donkey's years.

-Crandell

 

  to the Forums.

What Crandell has said above is FACT. To see just how it works, use your friend "GOOGLE" and type in "Joe Fugate". When you get to his website you will find a number of Video's and one of them shows how it works. He also has a wiring diagram for it, I believe.

I would definitely go with DCC. You do not need the biggest and most powerful for a small layout running 2 or 3 engines. After much humming and hawing and reading, I just went with the NCE Pro Cab for my 3' X 6' N scale layout. (I'm still wiring it in) Nearly everything that I read about it was positive. It is reasonably priced at $189.00 retail, but can be found at much cheaper prices and it can be upgraded down the road. It will happily run 6 of the newer loco's like Kato and Atlas with no problems even if a couple of them have sound.

Do as has been suggested and run feeders every 3' or 4'. These should be as short as possible. I used 22 Gauge telephone wire for these and soldered them to 18 Gauge thermostat wire that runs to the front of the layout where my 14 Gauge main buss runs the length of the layout. It may be a bit of overkill, but I had the wire from when I was an HVAC Serviceman before I retired. The main buss can be extended when I expand sometime in the future.

Good Luck and enjoy yourself.

Blue Flamer.

[selector]

I am happy you asked!

If you wire a 2.4 amp 12 volt tail-light bulb in series, it will become the limiting device for current flow/usage in the event of a short.

In my case, I have four benches arranged in a square with a central operating pit.  Each bench is fed via a sub-bus, off of which come the feeders...not directly off my main bus.  So, off the bus must come two robust wires that T into a sub pair of wires that serve the module or bench component.  The rails are gapped so that this works....each bench gets one sub feeding it via feeder wires coming off the sub and up to the rails.

The twin wire bridge from the main to the sub gets a tail-light bulb soldered into one of the two wires...matters not which one.  I simply cut one of them halfway up, and soldered one end to the nub at the base of the bulb and the other to the scored and roughened chromed sidewall of the bulb body (solder wouldn't stick to the shiny chrome otherwise...believe me, I tried).

Now, when a metal tire on the engine bridges two rails, say during a derailment at a turnout, instead of the short detection circuitry noticing and then shutting down track power, the light immediately begins to draw the current and quickly gets to glowing brightly.  This prevents the circuitry back at my base station from tripping, thus shutting down all those sound decoders around the layout, but it also pinpoints the short for me.  Look to where the bulb is glowing, and there is where the short lies.

Where the metal tire is shorting, there is the path of least resistance around the layout, and to that place is where all the electrons quickly and preferentially flow.  Except, they run through the light filament, and the rest is obvious.

It is a cheap and highly effective shorts management set-up.  Not my idea, incidentally...has been around for donkey's years.

-Crandell

[Centurion]

selector

But them cheap ol' tail light bulb's will glow every time.

-Crandell

 

Thanks everyone for the great advice. So Crandell, what did you mean by your quote above?

[Hamltnblue]

 Yup, I used 14-16 volts because of the DCC standard.  Also the heat is much higher than a light bulb. More like a 30-60 watt soldering iron. Heat is isolated to one small area.

[rrinker]

 Just a note, if you are doing the 'quarter test' properly it does more closely simulate a short where a metal wheelset might bridge the rails. You are supposed to just sit the quarter on the rails, NOT press down on it. Pressing down will give a nice solid short. ith the quarter just pressing down with its own weight, it more closely approximates a metal wheel or metal truck sideframe on a car that tips over and just lays on top of the rails. A typical locomotive would press down on the track harder than a quarter, as they typically weigh more (at least in N scale and up...). So, flip a quarter on the track and see if the booster/breaker trips. No cheating by pressing down. If it trips 100% with the quarter in various locations along the track, you're good to go. If it trips is some places and not others, you likely need more feeders or possibly a heavier bus wire. It's those shorts that draw 4.5 amps and don't trip the 5 amp breaker that are the problem - 4.5 amps at 12 volts is 54 watts. Ever touch a 50 watt light bulb? HOT!

                                   --Randy

[simon1966]

Sure you could get away with less amps now, but if the Chief gives you other features that you want, ie, the duplex wireless, dual knob throttle, etc, don't worry about it.  Use good wiring practice and the power management and you will be in fine shape, even if you only ran 1 loco at a time.

[MisterBeasley]

Centurion

Like I said, I will probably be running 3 or 4 locos, with structure lighting, switches, etc.

You should use your DCC system only to power your trains.  Structure lighting and turnouts should be run from a separate power supply.  Once you've got a bunch of buildings, yard lights, street lights and so on, you will be using more power for that than to run the trains.  Don't use that precious DCC power for anything that doesn't run on the track.

Excess power will not hurt.  It won't burn up locomotives, and will cause no damage if you've got proper circuit-breaker protection.  Sound locomotives use more power than non-sound locomotives, in general.  If you have passenger cars with incandescent lights, they will draw power from the tracks and must be accounted for in your DCC power budget.

I bought a 5-amp Lenz System 100 about 5 years ago.  I have a relatively small layout, and I typically run no more than 4 engines at a time.  I know I don't need all that power, but now that I'm building an extension, I'll be able to run more trains and I don't have to worry about it.

[selector]

But them cheap ol' tail light bulb's will glow every time.

-Crandell

[Hamltnblue]

This type of short is pretty common.  When you do a quarter test you are forcing a direct short which trips the breaker. If a wheel flange shorts it could only be a partial where there isn't enough pressure to cause a 0 ohm reading but maybe something close. The result is that you might draw 4.5 of the 5 amps and build up some good heat. 4.5 amps times 14-16 volts on the track equals about 60 to 75 watts of heat which is significant.

[retsignalmtr]

When I started to build my layout I planned to go with DCC and wired it accordingly with 14 AWG for the buss and 20 AWG track feeders. I went with Digitrax's Super Empire Builder 5 amp system. I did the quarter test sucsessfully on the entire layout. One day while running a train I received a phone call and left the train running untended for about 15 min. When I returned I paid no attention to why the train was no longer running until I smelled the pungent odor of melting plastic. The loco had derailed on a switch frog and a wheel was bridging rails of opposite polarity. A small section of the rail was glowing red and the ties and plastic truck on the loco were melting all while the red track power light was still lit. The switch was heavily damaged along with the locos truck frame. When everything cooled down I redid the quarter test at that spot and the power went off every time. My layout is N scale. I haven't had that problem again as I don't get too many derailments. I may put in a PM42 as the default setting is 3 amps per segment. On one hand you want to get the most power to the rails that you can, on the other hand you have to protect the wiring from drawing too much current than needed. The loco will draw only what it needs to run, but the circuit protection will only trip when the current level gets to the setting of the circuit breaker.

[cudaken]

 Burt, IMHO only time there is to much power is when the track is wired wrong. If wired wrong, any power is to much! I am the poster child for that mistake.

 I run a SEB that all so has 5 amps and some times I only run one engine with no ill effects.

 Couple of tips.

 Run no lighter than 18 gauge bus wire.

 22 gauge feeders no longer than 18 inches, 12 is better.

 Color code your wire for later when you want to change things.

 As you add wiring, do the quarter test to make sure the over load protector is working.

 What caused my problems was when I added a new section that was free standing to my layout. I wanted to test the new section and ran a 22 gauge wire 7 foot long to my power blocks. Never got around to changing to a heaver wire and started to eat decoders. Finally did the quarter test, protector was not kicking and and was letting the smoke out of the decoders.

 Now, every time I add a feeder wire, I lay a quarter (or a screw driver) across the new rails to cause a dead short, over load protector kicks in and I am good to go.

 Cuda Ken

[Centurion]

Hi All,

I keep seeing a variety of question and answers to how much power one needs to support their layout, but with all the varied opinions it starts to get a little confusing. Because I am just starting out, but know that I will be building onto the layout over time, I want to err on the side of more amps to start with. From what I have read at http://www.dccwiki.com it says that too many amps can cause damage to the loco, where other sources have stated that the loco will only consume what it needs.

With all that being said, I would like to purchase the following items knowing that I'm NOT going to smoke the couple locos I have on the small track that I start out with.

1. Digitrax 5amp Super Chief Duplex
2. Digitrax PS515 Power Supply
3. Digitrax PM42 Power Manager 

Like I said, I will probably be running 3 or 4 locos, with structure lighting, switches, etc. But it might be on a small 4x8 area or even a 2x8 module to start off with. As long as my wiring is good, and everything is tried and tested do you think I will be ok with the 5 amps? Again, I like to plan for the future and hope this will work. Any advice is greatly appreciated.

Thanks,
Burt