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Author Topic: Variable track voltages  (Read 1885 times)
cpengineering

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« on: September 30, 2011, 12:57:33 PM »

Hey all, I'm working on the California Polytechnic State University Rose Float team, and part of our design this year required the use of some electric train parts, which we actually got donated from Bachmann.

We're using the Large Scale Thomas & Friends trains since they are the biggest and therefore most stable wheel base. We're trying to make the train speed up and slow down at specific parts of the track, and if possible we would love to not need a controller/sensor to accomplish this. We were thinking of having sections of track be different voltages than adjacent sections, slowing down or accelerating the train as it passed over each section, but we haven't tested this yet and I'm worried this could damage the motor, and how we will accomplish this. Are there some sort of rubber isolators that you install in the track that would let you isolate a piece of track from the rest of the circuit? Would the only way to accomplish this speed variation be to program a controller to vary the voltage across the whole track?

If you guys can shed any light on our predicament or direct me where to go for the next step it would be much appreciated!
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Nathan

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« Reply #1 on: September 30, 2011, 01:45:02 PM »

Creating insulated sections of track with Bachmann Track will be a problem.  Once that is done you can create different speeds in different sections with a simple power resistor between the power pack and the section of track where you want the train to slow down.  The proper value of the resistor will take some trial and error, but you will want ones rated between 10 and 25 watts to be safe.

My large scale Thomas typically draws less then 1/2 amp, so it would probably take a two ohm resistor for a one volt drop.  Get a volt meter and measure the voltage on the track at the highest speed you want to run, then check it for each other speed and calculate the resistor from there.  You can also get some variable resistors say at 20 ohms and try different settings on each.
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NarrowMinded


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« Reply #2 on: October 02, 2011, 12:23:47 AM »

You wont damage the motor using simple resistors as mentioned in the other reply, if you were using brass track there are insulators made to join the track, if your using bachmann track it should be simple enough to remove the metal blade style joiners and install some made from plastic.

Remember to keep the bachmann track dry, it will corrode, I use a light "Conductive" oil I buy from the local train shop on my layouts and they run and run and run without stopping. I would also add a capacitor to the locomotive, this will do a couple things, it will help slow the loco more realistically at the speed change sections, and it will help keep your loco running at dead/dirty parts of the track.

I would seek the advise of forum member Jim Banner he is a wealth of information both in Electrical issues and Model train Issues.

NM-JEff
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NarrowMinded


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« Reply #3 on: October 09, 2011, 02:22:31 AM »

I'm surprised there has not been more replies on this post.

NM-Jeff
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g-guage_trains

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« Reply #4 on: October 09, 2011, 12:23:32 PM »

Well the easy way is to use separate power suppliers for each section of track with plastic insulting between sections. Get cheap transformers, like Bachmann starter set, for each section. Be careful that you one section set at high speed and second a very slow speed, bad for the motor. 
alanrr
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