# Track Voltage Monitoring Car



## gunrunnerjohn (Nov 10, 2010)

Here's my latest project. I'm building a voltmeter car like the series that K-Line put out. Mine is updated to the 21th Century, it'll have digital meters. The K-Line only has one meter, mine will have them on each side so you can see the track voltage from any orientation.

I started with an old beat-up Baby Ruth car, I'm putting trucks with pickups on it to grab the voltage, and I obviously painted the car. I've hacked the holes for the two meters, so I have to build up my comparator circuit for the voltage trip. It appears I'll have to have a little power supply to have a reference voltage for the comparator. I might use a zener diode and a divider to give me a larger range, haven't addressed that circuit yet.

The other addition I'm going to add is a strobe on the top that blinks if the track voltage goes below a set voltage, that will be adjustable with a pot inside the car.  Since I have a convenient voltmeter right there, I won't even need anything but a screwdriver to set the trip point! 

As many (most?) of you know, TMCC uses a steady track voltage, so this is useful to cruise around the layout and see how much the voltage varies, helps you to find trouble spots. I'm sure it'll light up on the ceiling track until I get all the feeders right! 

One thing I need for this car is some spiffy decals for the blank panels to "dress it up". Looking for ideas and sources.


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## x_doug_x (Jun 21, 2010)

LoL, I'd say jack daniels stickers!!


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## gunrunnerjohn (Nov 10, 2010)

I think that's been done, need something like a lightning bolt.


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## Big Ed (Jun 16, 2009)

gunrunnerjohn said:


> I think that's been done, need something like a lightning bolt.




Nice I never even knew they made one.:thumbsup:

I can hear the gears in T mans head clinking now.
I got to make me one of those.

Get some PRR decals search e bay I have seen them.:thumbsup:
It will go with the rest of your PRR cars.


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## gunrunnerjohn (Nov 10, 2010)

Actually, it was a PRR Baby Ruth car that I savaged for this project.  It was pretty beat up. I must admit, those old cars were made of some serious plastic! It is at least twice the thickness of the shell on a modern boxcar! It's also a clear plastic under the paint, another thing I found interesting. I wonder if more are like that, I could strip the paint and have a transparent car! 

Maybe a PRR decal and a lightning bolt, that would be cool.


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## Big Ed (Jun 16, 2009)

gunrunnerjohn said:


> Actually, it was a PRR Baby Ruth car that I savaged for this project.  It was pretty beat up. I must admit, those old cars were made of some serious plastic! It is at least twice the thickness of the shell on a modern boxcar! It's also a clear plastic under the paint, another thing I found interesting. I wonder if more are like that, I could strip the paint and have a transparent car!
> 
> Maybe a PRR decal and a lightning bolt, that would be cool.



Two lightning bolts...one for each side.:thumbsup:

I just looked for decals and saw none. But I have seen them in O before, you got to keep searching day to day.


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## tjcruiser (Jan 10, 2010)

Cool custom project. I've never seen anything like that before. Very creative!

TJ


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## novice (Feb 2, 2011)

These companies/entities use lightning bolts for logos:

Gatorade
Jolt Cola
San Diego Chargers
ACDC - the band
Lightning Bolt surfboards
Foo Fighters
Opel - the car

Any help?

That's actually a good idea for a car


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## gunrunnerjohn (Nov 10, 2010)

Well, I'm working on getting the voltmeters to accurately read the AC, I need a schottky bridge, so that's coming from Digikey.


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## servoguy (Jul 10, 2010)

John, if you want the meters to read the true RMS of the AC signal, you will need a RMS to DC chip. Rectifying and averaging the AC voltage doesn't give the right answer unless the AC is a pure sine wave. 
BB


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## gunrunnerjohn (Nov 10, 2010)

I realize that Bruce, but since the meters are powered from the same source as the measurement, I can't find a converter that will do the job. However, in tinkering with the setup, I can get pretty close with a Schottky bridge rectifier and a voltage divider. It won't be instrument quality, but I can get to about 5% of the RMS voltage over the 10-20 volt range. Since my use is really to monitor the 18V TMCC track voltage, I'll be tuning it to be accurate in that range.

The A/C should be a pretty pure sine wave, looks good on my scope anyway. Remember, this is coming directly from an AC transformer.

I considered the converter with a darlington behind it to actually power the meter with the real RMS value, but that's getting complicated. I'd need a power supply to power the whole conversion part.


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## servoguy (Jul 10, 2010)

I was kinda teasing when I suggested you make a science project out of this. I think this is a neat idea but I think the contact problems on the center rail my not give you a good reading on the meter.


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## gunrunnerjohn (Nov 10, 2010)

Well, I'm putting two pickups on the car, and I am also going to have a filter cap on the rectified DC to smooth it. I think that will give me a pretty stable reading, and I can size the cap to smooth it out.

There's a balance between the response and cap size, so that will be one thing I play with when I get it working.

I did connect the meter with a bridge rectifier and a cap to a passenger car with two pickups, it got pretty stable readings rolling around a small loop of track.


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## T-Man (May 16, 2008)

I would got with MacDonalds with the "Burgers sold" next to the screen.

Neat project. A similiar one was done with HO and it measured scale miles traveled. It was an article in an old Model RRer.

Good Luck

You Engine is testing fine. I oiled it today. The wheels will be next.


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## gunrunnerjohn (Nov 10, 2010)

I'm not sure how I'd measure miles traveled, I'd have to add a magnetic pickup on one of the wheels! 

What's wrong with the wheels on the engine? Did you ever figure out exactly what makes it work?


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## T-Man (May 16, 2008)

The wheels need to go back on.

I changed the engine coil completely. WIres and metal contacts. It may have had a bad connection, It did ratlle when it did not shift. I also cleaned all the connections between the bars.

Here is the link to the odometer.


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## haphall (Feb 1, 2011)

I'm guessing this is O based on the 'third rail' reference. I can see I could use one of these in HO as I start laying track and wiring up an HO layout. Can you post a quick and dirty circuit diagram as this gets closer to completion? So far, the circuitry sounds manageable. It's been 25 years since I tinkered with chips and diodes and such but they haven't changed that much I'm thinking. That's why God invented Radio Shack isn't it?
Used to write machine and hex when the 8080 series were the 'fast' chips.


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## gunrunnerjohn (Nov 10, 2010)

Actually, chips have changed drastically in 25 years, diodes not so much. 

If I were building that car, I'd use a rechargable battery and power it from track power. I'd also probably go simple and use a magnet and reed switch, which is used on many O-scale steamers. Cute idea.


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## gunrunnerjohn (Nov 10, 2010)

T-Man said:


> The wheels need to go back on.


I can certainly agree with that!



> I changed the engine coil completely. WIres and metal contacts. It may have had a bad connection, It did ratlle when it did not shift. I also cleaned all the connections between the bars.


I didn't expect that, but now that you mention it, the light did come on bright when it stalled. Of course, that would happen if the E-unit contacts were not working as well. I assumed the rattling was just the fact that the armature was free to move, perhaps a bad assumption.

I'm impressed you made it go, I spent a few hours tinkering with it and could never get past first base. That's not normal, I can usually beat something like this into submission. 



> Here is the link to the odometer.


Cute, not sure how useful it would be. I'd probably wimp out and use a reed relay, a programmable divider, then the display.


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## Cape T/A (Aug 15, 2012)

Very interesting read here! Kind of over my head with the electronics talk, I'm use to dealing with AC voltage between 120 to 4160 volts, I think I'll just strap my true RMS fluke meter to a flat car with some pre wired leads and go from there, haha.

Any finished product pics?


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## gunrunnerjohn (Nov 10, 2010)

I actually bought some different meters for the car, they had independent power supplies and were native AC meters. I actually had to buy a small isolated DC supply to power them, they required a supply that was isolated from the voltage being measured. 

Here's the car and the power supply module build to power the displays. There is an identical display on the other side so you can read it from any angle. The remaining chore is to print some catchy decals to complete the picture. It was built from an old beat-up Baby Ruth car, of course I had to add the power pickups to the trucks.


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## AG216 (Sep 28, 2011)

this is not a criticism, but why you didn't install the dial from inside?
the idea is pretty good! i think is a good tool to find out weak point in your layout!
Andre.


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## gunrunnerjohn (Nov 10, 2010)

I couldn't find a voltmeter that had a neater mounting. The design was dictated by the availability of reasonably priced AC meters. 

Since I did that picture, I did straighten the alignment of the meter, it was slightly crooked in the picture.


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## Kwikster (Feb 22, 2012)

Pretty slick idea there GRJ. Much simpler to find problems now.

Carl


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## Carl (Feb 19, 2012)

For use non-dialectically gifted, could you please list the components you used?


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## gunrunnerjohn (Nov 10, 2010)

The tricky part of the circuit is that I needed an isolated DC-DC converter, I used this one.

CONVERTER DC/DC 12V OUT 1W

I bring in track voltage to a full wave rectifier, then through a 12V regulator. The large caps are to keep the display from flashing with momentary track power interruptions. They just filter the DC and provide more even power.

I can't find the schematic or I'd post it, I know I drew one...


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## plandis (Oct 5, 2011)

now what you need to do is include some R across the test car so that you can pull 3-5 amps while you are measuring. that way you can "load" the circuit -the meter by itself will not and force the voltage drop across the bad connection you are looking for!!


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## gunrunnerjohn (Nov 10, 2010)

Well, you have to remember that "meter" is being pulled by a locomotive that does require current.


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## plandis (Oct 5, 2011)

gunrunnerjohn said:


> Well, you have to remember that "meter" is being pulled by a locomotive that does require current.


true- but for slow-mo individual thack joint troubleshooting is what I was thinking.


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## gunrunnerjohn (Nov 10, 2010)

If I'm at that level, I just go around with my voltmeter across 150 watts of 4 ohm resistor, plop that on the track and you have your answer.


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## plandis (Oct 5, 2011)

gunrunnerjohn said:


> If I'm at that level, I just go around with my voltmeter across 150 watts of 4 ohm resistor, plop that on the track and you have your answer.


10-4 and follow that with a soldering iron!! then agin, you could skip all that and do it on track laying day!


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## gunrunnerjohn (Nov 10, 2010)

Well, with enough drops, you don't really need to solder the track. For stuff that's hard to reach and I really don't want to go back, I consider soldering it.


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## old464 (Oct 12, 2011)

John, you should strip a box car with walnut shell and clear coat it!!! it might work well. 

take a few of the flashing blue LED lights like there is a bunch of welding going on inside the box car. it would be really cool a clear car with a bunch of blue lights flickering around. hmmmm I might do it myself! 

what era boxcar is this from?? good luck

thanks 
Chris


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## gunrunnerjohn (Nov 10, 2010)

As it turns out, that particular car was a clear plastic car. The base was an old Baby Ruth car, probably pretty early from the thickness of the shell, probably about 3/16", a serious chunk of plastic! 

Here's a current picture, I had to swap out the original meters as I couldn't get accurate readings. I found some better meters, and they give me pretty accurate readings. The remaining task is to invent some snappy decals, I think part of it will have to be a lightning bolt...


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## Carl (Feb 19, 2012)

Well, if does not work, you could build a model outdoor theater and use it for the screen 

The car does look great.


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## gunrunnerjohn (Nov 10, 2010)

Well, I can read it from across the room, I can tell you that!  There is another meter on the other side so you can see if from most places.

It's actually quite instructive to run it slowly around a track and see how the voltage varies.


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## Carl (Feb 19, 2012)

With all the great elctronic stuff you did...is a great car.

From a technical viewpoint, I agree it would be interesting to see the voltage variations. If I knew of the voltage variations, then I would be running around putting more power drops and abusing myself because I did a poor wiring job up front.


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## gunrunnerjohn (Nov 10, 2010)

Sometimes the voltage variations are due to other problems, connectors, dirty track, etc. This car was inspired by the K-Line voltmeter car. That one was an analog meter on one side, I figured this would be a better display and easier to use.


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## eljefe (Jun 11, 2011)

gunrunnerjohn said:


> The remaining task is to invent some snappy decals, I think part of it will have to be a lightning bolt...


Here are a couple railroads with lightning bolts in their logos.


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## gunrunnerjohn (Nov 10, 2010)

The Pacific Electric looks interesting. I'm thinking of a large lightning bolt and then some legend like a MOW HV Monitoring Car or similar. Haven't decided exactly what, or I'd take a stab at printing the decals.


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## eljefe (Jun 11, 2011)

Sounds like a San Diego Chargers car.










With your electrical skills, you could make it play this jazzy tune as it tools around! 

http://www.youtube.com/watch?v=whNOfvyPpaM


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## gunrunnerjohn (Nov 10, 2010)

I don't want no stinkin' Charger's car!  Now, if it would play the Eagles song...


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## plandis (Oct 5, 2011)

gunrunnerjohn said:


> I don't want no stinkin' Charger's car!  Now, if it would play the Eagles song...


... you can check out any time you like, but can never leave!


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## plandis (Oct 5, 2011)

gunrunnerjohn said:


> The Pacific Electric looks interesting. I'm thinking of a large lightning bolt and then some legend like a MOW HV Monitoring Car or similar. Haven't decided exactly what, or I'd take a stab at printing the decals.


how about something Tesla!!


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## gunrunnerjohn (Nov 10, 2010)

I'm thinking about one of these for the decal.


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## Hellgate (Nov 9, 2011)

I like the Reddy Kilowatt! 
That has my vote :thumbsup:


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## gunrunnerjohn (Nov 10, 2010)

It conveys the idea I was trying to capture.  I may add some text alongside.


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## eljefe (Jun 11, 2011)

Cool character. Kinda like Smilin' Joe Fission.


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## gunrunnerjohn (Nov 10, 2010)

I think the running one is the best choice.


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## plandis (Oct 5, 2011)

I still think you should put a min Jacob's ladder out the top or something..


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## gunrunnerjohn (Nov 10, 2010)

Well, generating the 2000 or so volts minimum to actually make that work would be an issue. I'd also probably lose control of all the trains from all the EMI!


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## plandis (Oct 5, 2011)

good point on the EMI. an automotive ignition coil (12X7K) ought to do the trick though. I've seen some small ones- should fit inside the car shell. you shoud be able to over-drive them by 50% -(18 volts) to give you 12K out! 

hey- wait a minute. didn't someone make an electrostatic track cleaning car? that would be HV. I wonder if that causes interference with the trainmaster control.


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## gunrunnerjohn (Nov 10, 2010)

I've never seen an electrostatic track cleaning car, and I sure wouldn't let one anywhere near my stuff! Both TMCC and DCS would probably react very poorly to high voltage arcing on the tracks!


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## Hellgate (Nov 9, 2011)

John,
I was wondering if you ever found your schematic? I want to either buy a kline or build one myself, but I would need the idiot's guide on how to build one.... maybe I wouldn't be the only one interested?


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## gunrunnerjohn (Nov 10, 2010)

I don't think I ever saved a schematic, but it's dirt simple, only four components.

The only trick to the car is the voltmeters from eBay require a totally isolated power supply, so I picked up this little 12V-12V Isolated Converter. I feed this with a bridge rectifier, three terminal 12V regulator, and a capacitor across the input to the regulator.


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