# power pickup from ball-bearing wheels



## mymodeltrain (May 14, 2013)

I just opened up a USA trains' passenger car to examine how power pickup is wired from the ball-bearing wheels to the bulbs. It turned out that the system has an electric board with more sophisticated connections than just a capacitor and a rectifier as I learned from the website. I hope to hear explanation from someone who has experience in this matter.


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## Greg Elmassian (Jan 3, 2008)

The wheels on USA trains streamliners are not ball bearings stock. 

Are you sure yours are ball bearings? 

My board is not sophisticated either. 

I suspect that your car has been modified... 

Is this indeed a streamliner? 

Greg


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## mymodeltrain (May 14, 2013)

Greg, 
It's a Virginia & Truckee Observation by USA trains. I am pretty sure, it has ball-bearing wheels. My question is why they need that electric board instead of using a capacitor and rectifier?


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## Greg Elmassian (Jan 3, 2008)

I went to the USAT site... the overton cars have metal wheels, and carbon brushes for power pickup on 2 of the 4 axles. 

Don't know about the circuit, maybe a regulator unit, or smoke unit. 

No ball bearings, list price is about 150, and ball bearing wheelsets are about 30 bucks for TWO axles... no way they came stock. 

Look carefully, do you think the ball bearings are in journals, because they certainly are not between the wheel and axle. 

Why not post a picture of the circuit board? 

Greg


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## mymodeltrain (May 14, 2013)

Greg,
You are right, I examined the wheels, it seems they are not ball-bearing wheels


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## mymodeltrain (May 14, 2013)

magnified wheel area


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## mymodeltrain (May 14, 2013)

car ceiling with lamps


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## mymodeltrain (May 14, 2013)

circuit board on the other side of the ceiling


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## Amber (Jul 29, 2011)

Well, the diodes are set up to what looks like a full wave rectifier and I'd bet the device with 3 legs is a voltage regulator so that the car will have constant brightness lighting.


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## Amber (Jul 29, 2011)

I just noticed the number 7812 on the circuit board. That means that the 3 legged device is a 12 volt regulator, because the 7812 is a common type of regulator.


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## Greg Elmassian (Jan 3, 2008)

Exactly... full wave bridge ensures proper polarity to the regulator. 

No filter or noise caps though... cheap... 

Greg


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## mymodeltrain (May 14, 2013)

Amber, 
Thanks for providing some clues on the design. And why the rectifier rests on piece of 6-leg metal?


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## Tenwheeler (Mar 5, 2010)

Voltage regulators are heat generators. The regulator is mounted to a heat sink to dissipate the heat of the regulator. Without the heat sink, the regulator would overheat and fail.


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## mymodeltrain (May 14, 2013)

Thanks all for the knowledge. I don't know much about electricity but I like to learn the mechanism how things work. It is clear that everything in the design has some purposes.


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## Greg Elmassian (Jan 3, 2008)

The 4 small black things are diodes (sometimes called rectifiers), this converts the track voltage to a known plus and minus. 

The three terminal thingy is actually an integrated circuit which is a 12 volt regulator that takes the track voltage and regulates it to 12 volts. 

When you do this, you create heat, and you need to spread the heat out over a large surface to get rid of it. 

Greg


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## mymodeltrain (May 14, 2013)

Thanks Greg, very helpful. Do you know where I can buy those diode rectifiers?


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## Amber (Jul 29, 2011)

Radio Shack usually has a fairly good selection of diodes available. They should also have those voltage regulators and other parts like that.


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