Maintaining Constant Voltage Around a Large Track

[toxicbananna]

Hi guys,

understand that the bigger the tacks for 9v trains, the voltage will drop at the far end of the track.

how to over come this problem? please advice!!

[peterab]

Most clubs run extra power connectors to opposite sides of the track, or to avoid very long wire runs just connect up a second controller at the other side. If you use two (or more for really big loops) controllers it's best to try and keep them set at the same speed. When hooking them up make sure you connect them up with the same polarity or they wont work, and they'll short each other out. If this happens just reverse the connector on one of them.

Hi guys,

understand that the bigger the tacks for 9v trains, the voltage will drop at the far end of the track.

how to over come this problem? please advice!!

[patje]

Hi guys,

understand that the bigger the tacks for 9v trains, the voltage will drop at the far end of the track.

how to over come this problem? please advice!!

hi

because I have a large layout

with 3 different tracks

I have 4 transformers installed.

not as an ordinary railroad (lego)

but in pieces

see colors on plan

the pieces are close to the transo's

and each piece can be arranged at the same speed

with a standard railroad

trains go slow an the end

and just beyond the transformer

then the speed go's better

here is that not the case ..

even more trains on the layout

and on the three tracks.

since they are usually ride on a different transformer

on the same layout and on the same time

insulate the tracks between the various transformers

with paper (polarity)

Edited August 19, 2012 by patje

[toxicbananna]

understand by using another power connectors at the opposite will maintain the voltage, the reason of not doing that is due to have to run up and down. i would like to just control it with one power source.

does modifying the controller helps? did anyone did that?

what is the factor to cause the voltage to flow thru around the tracks? more amps?

Most clubs run extra power connectors to opposite sides of the track, or to avoid very long wire runs just connect up a second controller at the other side. If you use two (or more for really big loops) controllers it's best to try and keep them set at the same speed. When hooking them up make sure you connect them up with the same polarity or they wont work, and they'll short each other out. If this happens just reverse the connector on one of them.

[tbroyd]

The power drop is mostly caused by tiny loses in each track joint, when you have a lot of track and joints the loses add up

Therefore the answer is to supply power using wires to several parts of the layout so that power at the furthest part of the layout does not rely on the track and joints. You only need one controller to supply a large run but need 3 or 4 feeds from the controller output to each corner of the layout.

[legoboy3998]

The power drop is mostly caused by tiny loses in each track joint, when you have a lot of track and joints the loses add up

Therefore the answer is to supply power using wires to several parts of the layout so that power at the furthest part of the layout does not rely on the track and joints. You only need one controller to supply a large run but need 3 or 4 feeds from the controller output to each corner of the layout.

It is not only the joints in the rails, but the rails themselves that cause voltage drop. When I was studing to be an electrician, we learned for long cable runs, you need to factor in the voltage drop caused by the wire. Even if you have a wire say 100 feet long with no joints, the voltage will be slightly lower at the far end, with normal electrical outlets, this is not noticable except on extremely long runs such as warehouses or other large buildings. The traditional model railroaders use a similar method as described above (running multiple track connectors from one transformer. However, they run a thinker bus wire from the transformer around the layout, than attach short sections of thinner feeder wires from the thicker bus wire to the track. this isn't really possible with LEGO unless you modify things.

IF your layout is really big, on solution may be to go from a LEGO 9V transformer to a model railroading 12V transformer. This would allow higher voltage to over come voltage drop over a long, long run.

Sal

WFB, WI

[1974]

A 12V transformer is definitely not recommended!

This will expose the 9V motors to 12V at the points where the transformers are connected, not good and they'll go too fast as well (until they burn out). If it was my setup, I'd measure the voltage along the track and insert more transformers where needed (any maybe add some diodes)

The LEGO tracks are indeed not good conductors and quite a bit of resistance wil build up. And as Ohm's law is V/R*A, the longer the track are, the resistance will go up (more R) and the voltage will drop (V) as the current draw (A) from the motor is constant

If one has a big setup like this, I suggest to learn some basic electronic knowledge (plenty of that stuff online) and buy a multimeter

[toxicbananna]

i do learn a lot from you guys, after thinking i guess i will need to pull a wire out to place in another sector.

also would like to know how the voltage split on a the cross section track?

my big track will consist of a big figure 8, could advice which point should i place the 2 connector? near the cross section track?

[1974]

How big is that figure eight setup? One transformer - with clean tracks AND clean motors - would be enough for quite a big setup

[peterab]

understand by using another power connectors at the opposite will maintain the voltage, the reason of not doing that is due to have to run up and down. i would like to just control it with one power source.

does modifying the controller helps? did anyone did that?

what is the factor to cause the voltage to flow thru around the tracks? more amps?

You don't have to use more than one controller, but you will need more wire if you don't. You can just connect up extra wires to multiple places around your loop all from one controller.

Some Lego train clubs do use modified controllers.

Mine uses a 3A 9V supply. This allows us to power more motors at a time. Some of the original LEGO transformers can struggle with more than two motors at a time (this varies from region to region too). We still connect to multiple places to overcome voltage drop.

There are also clubs in Europe who use up to 30V supplies. They do this to set speed records, and I suspect there is a higher risk of burning motors out doing this, or perhaps they modify the motors also.

[LEGO Guy Bri]

Does anyone have a diagram on running these extra wires from the controller and any preferred wires/gauge?

[toxicbananna]

understood with ur arrangement, would like to check how did u use a 3A 9V supply? change the transformer will do? or modification needed to be done on the controller?

also, the motor in our 9v is replaceable? as some of my motor are more then 10years old!!

You don't have to use more than one controller, but you will need more wire if you don't. You can just connect up extra wires to multiple places around your loop all from one controller.

Some Lego train clubs do use modified controllers.

Mine uses a 3A 9V supply. This allows us to power more motors at a time. Some of the original LEGO transformers can struggle with more than two motors at a time (this varies from region to region too). We still connect to multiple places to overcome voltage drop.

There are also clubs in Europe who use up to 30V supplies. They do this to set speed records, and I suspect there is a higher risk of burning motors out doing this, or perhaps they modify the motors also.

[peterab]

understood with ur arrangement, would like to check how did u use a 3A 9V supply? change the transformer will do? or modification needed to be done on the controller?

also, the motor in our 9v is replaceable? as some of my motor are more then 10years old!!

We've just changed the transformer. We had to find a plug to fit the controller (I think we cut it off from the old transformer) but otherwise it is really easy.

I was told the other day that the motors were easily serviced, but I've never done it since I'm mostly a 4.5V collector and Power Functions MOCer. 9V was my dark ages.

Unless the motors have obvious problems I wouldn't do anything. Some of the other forum members have had good success by opening the motors, cleaning and lubricating them.

Does anyone have a diagram on running these extra wires from the controller and any preferred wires/gauge?

Imagine a circle of 9V track with the standard power connector to the track. If you have a second power connector you can easily make an extra track connection and at the controller end the 9V plugs just stack. Too simple.

For larger layouts you just buy a bunch of 9V extension cables to get more distance.

[LEGO Guy Bri]

For larger layouts you just buy a bunch of 9V extension cables to get more distance.

Simple enough indeed. I was under the impression you guys were attaching non-Lego wires to the other parts of the track with all the talk about resistance building through the weaker connection points. I know that was in regards to track pieces, but I assume it goes similar for multiple cable connectors

[hoeij]

For the outer 9V loop on

I used 1 power supply, connected to 4 spots on the track. The lego 9V cables are much

too short, I use regular wiring from a hobby store.

I used a low speed setting on that track because I wanted the cargo train to run

really slow. As you can see in the video, at that setting, the train has problems

at one spot on the track (at the next speed setting, it runs fine, but then it goes faster

than what I wanted (perhaps this train should have been PF instead of 9V)).

In general, maintaining a near-constant speed, this is much easier for fast trains

(high speed settings) than it is at low speed settings.

The outermost loop is 12V track, it has less electrical resistance than 9V track,

so I used only two connections for that track even though it is quite long.

Edited August 20, 2012 by hoeij

[toxicbananna]

ok last question, will like to check how the voltage run in a cross section track, does the voltage and current go straight thru?(without splitting towards the left and right) or split to the left or right and straight?

[hoeij]

ok last question, will like to check how the voltage run in a cross section track, does the voltage and current go straight thru?(without splitting towards the left and right) or split to the left or right and straight?

There are wires in there.

[legoboy3998]

A 12V transformer is definitely not recommended!

This will expose the 9V motors to 12V at the points where the transformers are connected, not good and they'll go too fast as well (until they burn out). If it was my setup, I'd measure the voltage along the track and insert more transformers where needed (any maybe add some diodes)

The LEGO tracks are indeed not good conductors and quite a bit of resistance wil build up. And as Ohm's law is V/R*A, the longer the track are, the resistance will go up (more R) and the voltage will drop (V) as the current draw (A) from the motor is constant

If one has a big setup like this, I suggest to learn some basic electronic knowledge (plenty of that stuff online) and buy a multimeter

True. Hoever iT depends on the actuall rating of the motors themselves (just because LEGO uses 9V the motors themselves may be 12V (or some other volatge) motors) meaning they MAY be able to handle the increased voltage. Someone would have to check the specs. Either way, you could run the transformer at less than 9V, and only increase it above that , when the train slows at the far end of the layout. You could also replace the motors inside the 9V train motor case with a 12V one allowing all sorts of benefits.

Sal

WFB, WI

[JamesP]

V over R/I

Lego track has a resistance of about .02 ohm/section/way. (or .04 ohm/piece total).

That was when new values- I'd suspect them to be higher than that due to the connectors oxidizing over time. That means each 25 pieces equals 1 ohm of resistance.

9V mmotors draw around 650 mA stalled, so a 2 engine loco can draw about 1.2 Amps

So, 25 pieces of track away from the power plug in, 2 motors, 1.2*1= 1.2V loss in the track, or 7.8V maximum at the loco...

Best solution, is to add feeders. If you add one every 50 pieces or so, the maximum resistance the train will see is 1 ohm, but only 1/2 of the current, so 1/2 the voltage drop (or about .6v loss, leaving 8.4V at the loco).

A lot of this becomes vitally important when running DCC, because I have up to 60w on the track (12v/5A). And with 4 motors, the draw can be up to 2.4 A on any single area, or 1.2A/direction, and 25 pieces of track is about the practical limit for it.

I use a lot of different methods for connecting track, some of it uses fixed wires, some uses wire/lego plate, and occasionally I use the offical lego connectors. I have straight, curved and turnouts with electric feeds- my home layout is quite a convoluted arrangement for just using the lego feeds, and with ~930 pieces of straight track, if I just used the lego feeders, I would need 40+ connectors.

James

[JopieK]

With DCC it is very common to have boosters, even with smaller gauge, so especially with L-Gauge!

Check this: http://www.opendcc.de/index_e.html

[hoeij]

V over R/I

Lego track has a resistance of about .02 ohm/section/way. (or .04 ohm/piece total).

That was when new values- I'd suspect them to be higher than that due to the connectors oxidizing over time. That means each 25 pieces equals 1 ohm of resistance.

9V mmotors draw around 650 mA stalled, so a 2 engine loco can draw about 1.2 Amps

650 mA will kill the motor quite quickly!

A more typical load is 200 - 250 mA. My Maersk train (

) is about 10 feet long,

has two 9V motors. The two motors combined draw 420 mA (in the video, it is at speed setting #2 which means 4.2 volt,

but there is one corner where it slows down; one more wire needs to be added there) (the current 420 mA stays almost

the same regardless of speed setting).

At speed setting #3 (5.4 volt) it runs faster than I want (I want my cargo trains to go slow) so I have to

go with #2 (4.2 volt). But at about 3.2 volt it runs slower than I want. So the voltage drop must be less than 1 volt,

which, at 0.420 amp, corresponds to only a few ohms, meaning that quite a few wires are needed for this loop (I'm using 4

wires, and get practically a constant speed on the loop except in 1 corner; one more wire is needed).

Edited August 27, 2012 by hoeij

[JamesP]

Max from the motor site is 950mA, and I have burned out enough 1A decoders to believe that at 12V, I can draw more than 1A (RMS numbers) with the motors. I tend towards very heavy trains, so...

Again, from where I am sitting, 600mA is about the most I would want to run them at, and those give some good values for voltage drop. I don't generally worry about measuring the current, I just do it based on # of cars that I am pulling. 600mA*9=5.4W, and that means about 2w each motor for tractive effort(based on the motor web site). 4w isn't that much when you have 3-5 kg trains.

I use 4x motors on my Super Chief, in order to get enough power to climb hills-total of 8w mechanical available, and that would imply a rate of climb around:

746/8=.01hp,

33600*.01hp=

360 ft/lb/min

/7.7 (lbs)

=46 vertical feet/min.

Trust me, the Super Chief doesn't climb 46 ft/minute ! It might make 5 vertical feet in a minute though...which is probably a reasonable assessment of what actually happens.

A lot of the numbers I did are on LUGNET, around 1999. (why yes, I did the research a while ago...).

James Powell

[hoeij]

Again, from where I am sitting, 600mA is about the most I would want to run them at, and those give some good values for voltage drop.

I think that the 600mA (on one motor) is about a factor 2 higher than the actual value, and the

resistance of the track you mentioned is about a factor 2 lower than the actual value;

this cancels out, meaning that the voltage drop you calculated is correct.

The stalled current listed on the motors website occurs only if you hold the wheels completely still,

and put a full 9V on it (to do this experiment you need a different power supply, the standard 9V

controller can't produce the amps needed to get to 9V in this experiment).