# novice knows nothing of polarity

Discussion in 'Getting Started' started by kazi, Mar 20, 2007.

1. ### kaziNew Member

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We have an o gauge track at my work, we tried to run two trains simultaneously and no matter which direction they faced the second engine always ran toward the first. It was quite interesting does anyone know why this happens and can it be fixed. the trains are a different make, and theres a shop next store that also has a track and when we ran the second train on theirs it ran the same direction as the first. i'm interested to fix it and also the scientific principle behind this phenomenon, polarity i assume. thanks, a rank novice
2. ### Russ BellinisActive Member

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Are you using 2 rail dc o gauge or 3 rail Lionel/MTH/K-line ac o gauge?
3. ### kaziNew Member

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novice

2 rail o gauge
4. ### TriplexActive Member

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Sounds like one engine had the motor wired backward (or the pickups - amounts to the same thing).
That is strange.
5. ### Russ BellinisActive Member

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It sounds like your layout at work is divided into blocks and one block is wired backwards, or has a direction switch set backwards.
6. ### Jim KrauseActive Member

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The normal sequence of events would be for both locomotives to run in the same direction on a single track. If one locomotive was wired opposite of the other, they would run toward each other. Without knowing how your track is wired from the power supply, its hard to figure out what's going on. If you have what are called "blocks", divided sections of track, you should have two or more power supplies since each locomotive requires it's own power with a block system. Is your track just a simple loop or do you have sidings or double tracks?
7. ### TorpedoMember

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Does this mean you only ran the second train on the shop next door's track, but not the first, and it ran a different direction on that track compared to your company's track? If so, it strongly suggests that your two locos have their wiring reversed, either at the motors of the pickups, as suggested, and the track next door is wired with its polarity reversed compared to your company track.

If that is the case, there is nothing really strange going on. Just reverse the wiring in one of your two locos, and all should be well.

As to the scientific principals involved, A DC motor's direction of rotation is determined by the polarity of the voltage applied to it. Reverse the wires, and it turns in the other direction. Reversing the wires changes the polarity, and the electric current flows through the motor in the opposite direction causing it to rotate in the opposite direction, thus changing the direction of travel of the loco
8. ### kf4jqdActive Member

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I should really know this question. It's a basic electronic and physic's question. I am going to give it stabe at it. A motor just like a light bulb has no polarity to make it work. Polarity is used in DC circuits. You have a positive and negative. Ac has no true polarity. If you connect AC to a scope (oscilloscope) you will see a sin wave. You do the same thing to DC. You will get a flat wave. By the way, if you turn on and off DC to a scope. You have created a square wave. This is basic function off ALL computers!:thumb:

Now back to the motor. A motor has no polarity. It doesn't matter which way it's on the tracks. If the DC hasn't change. Nor will the direction of the locomotive. No matter which way it is placed on the track.

NOW! If you change the polarity of the track. It will change the direction of the locomotive. The winding of wire inside the motor makes this work. When you change the polarity of the track. You also change the electromagnetic field of the motor.

In Electronic Theory States: The Protron (positive) will flow to the Eletron (Negative)
In Eletron Theory State: The Electron will flow to the Protron.

Please not only crazy engineers will use the Eletron Theory when it comes to electronics. Almost everyone uses the Electronic Theory.

I hope I didn't confuse anyone with this.

Andy
9. ### TorpedoMember

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Current flows from negative to positive in solid, as opposed to liquid, metallic conductors (wires). The electrons move, not the 'protons.' The term conventional current flow is used when discussing positive charge movement, or hole flow as it is sometimes called, in non-metallic and liquid metallic conductors. People who understand this are not crazy.

Please take a look at this Wikipedia entry, especially the paragraph titled "Current in a metal wire."
10. ### cidchaseActive Member

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Speak for yourself, Torp. (insert smilie here)

The DC mtr runs CW or CCW depending on polarity. When you pick up a loco running fwd, and turn it 180,
the polarity is reversed, the mtr runs in the opposite direction, so the loco goes backwards.

I understand this, and I'm crazy. (just ask my ex)
11. ### Gary S.Senior Member

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Here's the deal on current flow... back when the old guys discovered electricity, they had no idea about electrons and protons. They had no idea what electricity consisted of. They could only note its effects and make theories from that. They arbitrarily chose "positive" and "negative". Then they said that things in nature tend to go from a higher energy state to a lower one, such as a ball rolling downhill. So, they decided that current flows from positive to negative. Unfortunately, they got it wrong. The electrons which are on the outer portion of the atom flow from the negative side of the source to the positive. The protons in the nucleus are essentially staying pretty much in the same place. As with all things technical, there is a possibility that I have no idea of what I am asserting.

And for the loco in question, some further experimentation is in order. The exact same experiment needs to be performed on the the two different tracks, and I am willing to bet that the results of the experiments will be the same.

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