# transformers ?



## daddog (Jan 15, 2013)

Hello railroaders. I am relying heavily on the "there are NO dumb questions" line in the beginners forum introduction for these questions. < I have LGB starter sets and extra track. A friend has Lionel equipment and offered me a large transformer to use with my LGB stuff. What transformer are interchangeable? Are the All different? > In the case of an actual (real) steam locomotive, the black smoke from the smoke stack is from the burning of the coal or wood, and the steam from the smoke stack or near it is evidence of the excess pressure in the boiler being vented off by the pressure relief valve and the steam horn or whistle when activated by the operator? Is this correct? Thanks guys, I appreciate being able to learn through you! john dd


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## Randy Stone (Jan 2, 2008)

So long as the transformer is DC output, it should run the LGB train. DC output should be 12-20 volts. If the terminals say AC output, it will not work.


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## Totalwrecker (Feb 26, 2009)

Your asessment of the prototype is generally accurate. 
The smokestack exhausts both smoke and steam. The steam is routed from the cylinder exhaust to a nozzle under the stack, pointing up and facilitates combustion by creating a draft. 
Steam also emits from the check valve on the steam dome (where dry steam inside is collected for power, water from wet steam creates problems). Also seen venting from whistle and generator. 

Smoke should be light, dark smoke indicates; a poorly fired, just starting loco or added strain on pull. Sometimes you'll see a puff of black smoke and that's usually when the fireman tosses a shovel full of sand into the fire, the draft carries it through the tubes and it cleans out soot. Clean pipes steam better. These are generalizations, some one will always have an exception. 

John


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## chuck n (Jan 2, 2008)

Unless the transformer came with or was made for Lionel's short lived venture into large scale, it will not work. As was stated earlier LGB and all other large scale runs on DC. Lionel 3-rail is AC. With AC your engine will just sit there trying to make up its mind whether to go forward or backward (60 times a second). This could burn up the motor. Chuck


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## ntpntpntp (Jan 14, 2008)

Be careful about terminology: a transformer is the bit of kit that reduces the mains voltage to something safe to use with our model trains. It usually outputs AC but may include a rectifier in the same box in order to output DC. A controller or throttle is the bit of kit with a knob, lever, slider or whatever which is used to control the movement of the model train. A controller requires a low voltage power feed, this could be AC or DC. 

It is quite common to have the transformer and controller combined in a single physical box that plugs into the mains and outputs to the track. As has been stated, for LGB you need a controller which outputs DC at up to 24 volts.


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## Dan Pierce (Jan 2, 2008)

Lionel uses AC and that is provided by a transformer. 
A power pack is the term for DC control as there is a transformer, but more parts (rectifier, capacator, etc.) involved to get DC to the rails, thus the name power pack. 
And newer higher power supplies have DC to DC converters inside to provide constant power output, and are still called power packs. 

So, there are units with low current/power output for train sets with a transformer, diode bridge, capacitor and speed control built in and are usually .5 amp to 1 amp in most starter sets. 

When more power is needed for bigger trains, you need a robust power source, and a speed/direction control which can be a single unit or separate units, and even radio control. Of course the more power and features you get, the higher the cost.


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## daddog (Jan 15, 2013)

ok guys you were good with the explanations, on both questions. Regarding the transformer question, my longest total track length will be about 100 feet. With no more than 2.5 percent grade, pulling 10 cars, what amps will be slightly MORE than I will need. Any ideal transformer that I should be looking for? My set is in the basement, maybe one of you garden layout people have a transformer that you out grew and would sell to me? Thank railroaders for all the help. john daddog


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## chuck n (Jan 2, 2008)

How many engines are you planning to run at the same time, will they have smoke, will they pull lighted cars? Before we can really answer your question we need to know what you want to run. As a rule of thumb, figure 1 amp per motor. If the engine has 2 motors that's is 2 amps. Smoke and lights take more. Most of us recommend a 10 or 15 amp "power supply". I use Bridgewerks, but there are also others on the market. Chuck


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## JPCaputo (Jul 26, 2009)

One of my old standbys is variable power supply using a transformer and some circuitry, home built. Pretty much it is a converted heavy old car battery charger that I've pushed 10 amps or more through it. It is diy, but costs about $15 in parts plus the car battery charger, so for possibly under $30 you can build a linear power supply.


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## daddog (Jan 15, 2013)

thanks guys for the information. sounds like more is better. with your helpful advice, I now know what to look for. john daddog


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## chuck n (Jan 2, 2008)

Power requirements grow as as trains grow. It is better, in my opinion to buy one power supply now that will support future requirements, than a minimal one now and 
new one with more amps later. Chuck


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## daddog (Jan 15, 2013)

Hi JP. Thanks for the input regarding the transformer. Any chance of some details on the "circuitry" involved? I have basic electrical background and can solder ok. Thanks, even if you don't want to go into detail. You have helped with the idea already. john.


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## BigRedOne (Dec 13, 2012)

If you spend some time now thinking through where you wish to take your railway in the future, it can save you some wasted time and money due to going down dead-ends. Like Chuck said. 

So, I suggest looking into the merits of DCC and battery powered options (or boiling water!) before taking a plunge. I've found my assessment of the relative merits of these options is evolving. 

The basics of variable-voltage track power are thus: 

1. Transformer to reduce house voltage to something appropriate for the model railway (with sufficient capacity to support the current draw of the railway.) In large scale, this is typically close to 24 volts, though a bit less may be adequate. 
2. Rectifier to convert AC to DC. 
3. Some method of varying the output voltage. 
4. A method of reversing the polarity of the output voltage. 
5. A fuse or other protection from excessive current draw - which can be a serious risk, depending on what you've cobbled together. 

Some of the above can be omitted if the train only need operate at a constant speed and direction. 

I like constant illumination, so my loyalty is more toward DCC, or battery, especially since I plan to run live steam too. If there's still a lot of track acquisition in your future, battery can run less expensive aluminum track.


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## JPCaputo (Jul 26, 2009)

For the circuitry, most of the variable supplies I build use either an lm317 or lm723 as the main element. They are variable regulators. I don't know how to put links on here, but a search of their data sheets will give manufacturer reference designs to use. 

A pass transistor setup on the output can increase the current to any amount desired.


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## Dan Pierce (Jan 2, 2008)

The lm317 is good for 1.5 amps. LM350 is good for 3 amps. LM338 is good for 5 amps. 
So, no pass transistor is needed for 5 amps, just use the LM338. 

And add step 2a above for a filter capacitor to smooth out the DC pulses. 
I use 1000 microfarad per amp, so a 10 amp supply will have 10,000 microfarad capacitor with 35 WVDC rating.


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## JPCaputo (Jul 26, 2009)

One note that i have found out over the years. Calculate the maximum power dissipation ( Current x DC voltage of the power supply) and get a heat sink rated for 1.5 to 2x more power to allow for other than ideal conditions. These are "linear regulators" that have to dissipate the voltage drop as heat. This will keep fingers from getting burnt by touching the transistor or heat sink. Main thing is to keep the regulator relatively cool ( under 55C-60C ~ 150F )


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## Dan Pierce (Jan 2, 2008)

Current times voltage of the power supply is not what the LM series dissapates as heat. 
The real heat is the voltage difference between the regulator and power supply. 
So, a 5 volt regulator on a 12 volt supply has 7 volts times the (LM350) 3 amps for 21 watts maximum. 
The power supply could be 12 volts at 20 amps which is 140 watts. This is not what the regulator sees.


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## JPCaputo (Jul 26, 2009)

I agree completely for fixed regulators, being difference in voltage x and current the regulator can handle. I was wrong about using the full power supply current. 

I use the full power supply voltage because a variable regulator such as the lm317, lm350, lm338 can put out ~1volt minimum. 

With an lm350 running a 1 volt output with 12 volts input, the dissipation would be 33 watts. Just shy of the full voltage x rated current of the regulator.


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## Dan Pierce (Jan 2, 2008)

The heat factor is 0 watts if no current is drawn, 33 watts only if the current drawn is 3 amps in the above example and the max voltage rating has nothing to do with the heat generated. 
What matters is the power supply voltage and if the power supply is 30 volts with a 5 volt LM350 output and 3 amps drawn, the wattage will be 25 times 3 which is 75 watts, and this is half of what the LM350 case can handle if heat sunk properly.


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