# voltage help



## gobucks1a (Mar 5, 2011)

I have two lane tomy track with a tri power pack for each lane. As recommended, I am testing the volts thru out the track. I used a rubber band to hold the controllers at full throttle.

At the beginning level the power pack says 8v. My questions for the ones who know.... When I went around the track I had readings of 12 for both lanes. the power pack says 12 v is the middle level, yet I had the power packs on beginning level?. 

Also, when I went around the track. One lane was reading at 12.00 and just below it. The other lane had readings of 12 and often readings of 12.02. Will that difference, 12.02 to 12.00 and a little lower, result in significant differennce in the speed? or is it to small of a difference to even notice.

thanks in advance for any help you may have.


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## Rolls (Jan 1, 2010)

You've given a very clear and concise description of what's going on with your track, so it's easy to offer help.

Going around the track with a voltmeter to get readings is a good idea. The one thing to do differently is to try to get some current running across the rails where you're taking the measurement. You can do that by touching the leads of a resistor across the rails and then taking your voltage measurement. When a little current is flowing, say .25 to .5 amps, you'll see the tri-power pack put out something closer to the 8V you'd expect. Also, if there are weak connections around your track, like at track joints, the voltage you read will be lower as you test points farther from the power pack.

What size resistor? V=IR, so R=V/I, so if you want to draw .5A with the tri-power pack at the 8V setting, 8/0.5 is 16 ohms. At the 22V setting, 22/0.5 is 44 ohms. You could double those resistor sizes and draw only .25A and still get very good information about voltage around your track. 

Resistors are commonly sold in 1/4 watt sizes. Those will get hot fast or even catch fire if you run too much current through them. It's better to get a 5 or 10 watt resistor for your testing purposes. This is because resistors turn electrical power into heat when current is running through them. Power is just V x I. So by putting 8V across the 16 ohm resistor above to draw .5 amps, the resistor will need to dissipate 4 watts. It'll get hot to the touch after only a few seconds, but that's all you need. You could do all your testing with a single 50 ohm, 5 watt resistor. Some folks use light bulbs with jumper wires to provide the resistance. And the easiest shortcut is to just put a car on the track with the back wheels lifted when you measure voltage, though some folks frown on revving motors like that with no load.

Bottom line is that once you get a little current flowing through the rails, your voltage measurement will be more realistic and help you verify that your track power distribution is honky-dory. 

Last, the .02V difference you asked about is not significant. Don't worry about it. If you see only .02V difference between lanes when measuring on the far side of the track once a half or a quarter of an amp is flowing, you're doing great!

Hope it helps,

Rolls


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## gobucks1a (Mar 5, 2011)

Rolls you have this down pat don't you. After reading your post several times, I hope I can communicate correctly my questions.

So, just by holding the controller down this will not get the juices flowing in the best way to measure my voltage. I am not against holding the back tires up in the air and revving the car. 

My track is on a 4 x 8. I built a design from greg braun's hoslocarracing site. the track desing is River Hills 50. The track does a lot of back and forth. As a result I could reach most of my track from my terminal track.

When using a car as a resister, do I need to rev it in the same area as my reading? Also, how far apart should I do my readings? i.e. every foot etc

Thanks again for your help.


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## Rolls (Jan 1, 2010)

Good questions...

First, no change in how you did your controller setup - still want to have the rubber band on 'em to let the power flow. (But until there's something across the rails that lets current flow, like a car or a resistor, no power will flow. Think of the rails as just two long, weird-shaped terminals of a battery - nothing happens 'til there's something held across those terminals to complete a circuit for current to flow through.)

Second - yes, you're right. You want to hold the car in the same place you take your reading. That'll tell you what voltage the car sees in that lane when it's at that point on the track. Try it at 3 or 4 places around the track... if the voltage readouts (with current flowing) are the same, you're probably in pretty good shape. If you get a significantly lower reading at some points, or if many of your cars seem to slow down at specific points, then you'd want to zoom in on that point and the track pieces around it to see where the cruddy connections are.

Do you have just the one power terminal from Tomy, or have you added (wired in) any additional power taps?

The River Hills 50 is a nice layout, btw!


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## gobucks1a (Mar 5, 2011)

Rolls, thank you again for you help. My lads and I are simple racers. We set up the track with the 4 prong track terminal that allows you to have one tri power pack for each lane. All of the track and power packs are Tomy.

I purchased the parma econo controllers, but, have not use them. Right now my young ones can full throttle the super g cars around the track without worries of a crash. I inturn, race them with my vintage afx cars. I will up the power pack in my lane to middle or top speed so I really have to watch what I am doing.


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## Rolls (Jan 1, 2010)

That sounds like a great set-up, gotbucks. My lads and I are simple racers, too. 

I was surprised that I was able to get away with only the normal power terminal and no taps for a long while on my 119' Tomy 4-lane with lots of elevation changes. 

When I finally got to the point of the build where I could spend time wiring in 2-3 more taps, of course it was more reliable and could better withstand expansion from severe temperature swings and frequent bumps into the table by fast-growing pre-teens, but overall I have been extremely impressed with the electrical connections in Tomy AFX track. With very little maintenance we had very little trouble for many months before power taps, in a rather harsh track environment. No complaints!

Have fun!

Rolls


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## gobucks1a (Mar 5, 2011)

Rolls, another question. Do you use any timing hardware? As you say you are but a simple racer like my clan. I think it would be great to able to record lap times so when you fix up or tune up a car you can have tangible evidence it worked.


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## Rolls (Jan 1, 2010)

BTW, since you have only the double power terminal and no additional tracks, it's easy to use another trick to check your connections. Just pull back on the section of your track that comes to the back of your power terminal to disconnect it, then run a car from the power terminal around the full circuit to see where and if it slows down or stops. If it does, the track connection before the slow-down or stop is suspect and could use a cleanup or minor bend of the z-rail to restore good contact.


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## Rolls (Jan 1, 2010)

gobucks1a said:


> Rolls, another question. Do you use any timing hardware? As you say you are but a simple racer like my clan. I think it would be great to able to record lap times so when you fix up or tune up a car you can have tangible evidence it worked.


Lap counting and timing is great fun. I don't mind tinkering, so I built a light bridge and used IR photosensors and Greg Braun's free LapTimer 2000 software to do it. It really adds to the fun, I think.


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## Rolls (Jan 1, 2010)

gobucks1a said:


> Rolls, another question. Do you use any timing hardware? As you say you are but a simple racer like my clan. I think it would be great to able to record lap times so when you fix up or tune up a car you can have tangible evidence it worked.


For more detail on my lap counting adventures, see this post.

Take a minute to read the reply posts following it, too, for more good info, specifically *rbrunne1*'s experience and *AfxToo*'s excellent post on the inherent tradeoffs in lap timing approaches, too. Good stuff! 

Might be helpful if you're at the stage of thinking about lap counters.


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