Testing voltage and amperage drop at points on layout

Yes, you need a load to test the voltage drop. I have used a brake light bulb from an automobile to make a load. You want to use something that draws around 4 amps or more for a load. One time I used an automobile headlight, but that may have been too much of a load.

To eliminate voltage drops you can:

-use heavier wire. What are you using now?

-make more power feed connections. This is especially true if you are using Lionel fastrack, as it develops poor connections at track joints

The reading on the Z-4000 are the reading at the meters on the transformer. There is no way the transformer can measure the voltage on a remote track section.

The amperage shown on the Z400 should be the load on the transformer correct? Connect a pocket voltmeter near the locomotive or caboose to read the voltage there momentarily. If you have an MTH loco you can read the voltage the engine is seeing with the DCS handheld.

The easiest way to screen for this problem is simply to connect your voltmeter to the track in the area where you think you have a problem, and run the  normal train all around the layout and over the problem area while watching the meter. In normal circumstances the voltage will drop as the train goes past the voltmeter. I personally like to see a drop of not more than about half a volt for PW stuff. You can tolerate more with command/cruise control stuff.

The secret to all this is to pick ONE meter and use it to measure all the voltages at all the locations. Using the meter or display on a transformer and comparing it to the reading on a handheld meter or meters will only cause frustration - guaranteed.

In the type of circuit we are discussing, there really is no such thing as "amperage drop."

I use an auto headlight (or whatever) to place a steady electrical load (2+ amps) on the track at the point furthest from the track feeds, then push this car around to check for excessive voltage drop across rail joints. The car can be rigged to test across center rail joints or running rail joints, with voltmeter leads to center rail pickups or wheels on each truck. The trucks are insulated from each other.

You can do the same testing manually, but this test car made it easy to check a lot of track expediently. Sometimes you can just feel for heat in the rail joints (with steady electrical load applied furthest from the track feed) - don't get burned!

If you have more than one power feed to the track, I would think that you need to move the load about with the volt meter.  I would use something like ACE's car above with a tail light bulb or two to provide a load on the car so that the load is at the point of reading.  

JGL

Tow this around and for a load, drag a car with a 50 ohm power resistor behind it.

Thanks, I am getting a better idea of how to do this.

So, the "benchmark" voltage and amps would be a point closest to the transformer (shortest run of wire); and once measured, then proceed to move the lamp or other load to other points further away - take a measurement - and move on? Does that sound right?

Right now the wiring  is all 16 gauge - and I very well may need to increase that to  14 gauge as I expand into the utility room area (50+ foot runs of wire) - but I want to see how the existing wiring is performing.

You want the load to be with the voltage reading, that way you can see where the voltage drops are.  If you're measuring voltage on the opposite side of the layout, you want the load to be right at the measurement point.  That gives you the real picture of voltage drops.

There really isn't an amperage drop, per se. If you have a voltage drop, the amperage will go up. Just throttle down the transformer and watch the ammeter go up (in command control).

The amps just make the voltage go away.

Guys, I used a command control engine - caboose, and lighted passenger car to create a load ~ with smoke unit on about 2 amps at transformer ~ and ran engine and cars around and stopped and tested at various points ~ at most there was just one volt drop - if that. Unless I am not doing this test correctly it appears the 16 gauge wire hook ups (even ones at 50+ft. lengths) doing a good job - or do I need to increase the load to get an accurate test?

What do you guys mean that the amps will go up if there's a voltage drop? How do you determine that from the meter? Or, do you mean in general electricity terms when voltage drops amps have to go up in order to power the load?

BTW: on my meter there's a note that says "add 14 db" - when volt range is set at 50: what does add 14 db mean?

Also, if I test using a PS2.0 engine set to DCS signal will that test tell me how voltage is dropping or only DCS signal strength?

When you have a greater current draw, for the same amount of wiring resistance, the voltage drop will be greater in the wire.  That's what was meant by the comment about amps and voltage.

Forget about the dB comment, it's not significant when reading AC voltage.  I take the DCS track voltage readings with a grain of salt, a real meter is the way to test them.

Thanks John.

Now, I have to figure whether to continue to use the 16 gauge wire for the remaining hookups ~ only 3 more pairs of wire to go to finish this project - but they will be close to 60 ft in total length. Do I use it or bite the bullet and go buy some 14 gauge. Since I am soldering the feeders in about every 15 feet on this layout I think 16 gauge is fine, but am I taking a gamble?

Paul, with just 2 amps or so for a load, you won't see much drop at all, less than 1 volt at 50 feet.  Unfortunately that doesn't tell the whole story, as that voltage will drop much further with a higher load.  If you're designing for the 'typical' 10 Amp circuit that folks seem to like for their layouts, you can expect about a 4 volt drop at max load.  with 14 gauge wire this will be about a 2.5 volt drop with the same 10 amp load.  

You can plug all the numbers in HERE (Voltage-drop calculator) and get reasonably useful results.  The numbers may not be exactly perfect, but they are close enough for this.  

Something I would consider doing, if you already own a substantial amount of 16 gauge wire is to run 2 or 3 parallel sets of the 16 gauge over the long run, all connected together.  Then at the remote end of the wire use a set of relays to switch on and off each track which could be powered from pretty much any gauge wire you like.  a pair of 16 gauge wires will out perform a single 14 gauge.  

As an example, over 50 feet, 18 VAC, and 10 amps, you would need 10 gauge wire to limit to a 1 volt drop.  The same thing can be done with four 16 gauge conductors in parallel.  As a note, I do not believe that a DCS signal would be effected by parallel runs of wire going to the same place, but I do not know this for certain.  

In the end, it would be worth while to figure out what the highest current draw you will have in normal operation will be, then wire for minimal voltage drop at that current.  If your trains typically draw 2 amps, a single 16 gauge feed will be fine for less than 1 volt drop.  If they run 5 amps, you'd need 12 gauge wire for the same amount of voltage drop.  

JGL

Opinions are like ___________ , everyone has one.

Agree to a lightbulb as a load. I use a caboose with an incandescent light bulb. In my opinion, you have more flexibility with your meter in your hand over on a piece of rolling stock. I was able to find bad ground (outer rail) connections that way. Found a massive voltage drop in the center rail of K-Line Shadow Rail O72 switches with this method.

In my opinion, if you are going to go thru all the agony of dragging more wires thru your layout, i would use 14 or 12 gauge THHN, common house wire. Why? Because you can use the same wire for working on your house. Up to you on whether to use solid or stranded. I prefer solid, but it is more susceptible to 'work-hardening', the more you wiggle it back and forth, it gets harder and more brittle until it breaks.

Thanks for the additional information...obtaining a higher amp load is challenging, although I guess I could string together a bunch of lighted passenger cars.

Update, I was able to create a 4 amp load for testing - and voltage drops ranged about 2 volts. This was for areas wired with 16 gauge wire ranging from 30 to 50 feet in length. For my last layout section that will require 55 to 60 feet of wire I may buy some 14 gauge wire, gotta see what's available.

Paul Kallus posted:

Update, I was able to create a 4 amp load for testing - and voltage drops ranged about 2 volts. This was for areas wired with 16 gauge wire ranging from 30 to 50 feet in length. For my last layout section that will require 55 to 60 feet of wire I may buy some 14 gauge wire, gotta see what's available.

If you have access to old extension cords, you'll have an inexpensive source of hook up wire.   

A convenient way to place a steady load on the track is with an old automotive headlight. The high-beam connector prongs can be bent to contact the rails as shown, without clip leads. Turn the voltage up to no more than 14.4 volts. A larger load makes it easier to find excessive voltage drops across rail joints. Any more than about 0.05 volts drop across a single rail joint should be corrected, if there is a lot of track with few feeders. Remember, place the load furthest from the track feeders and measure voltage across all the rail joints in between. For testing purposes it will be better to only have one track feed point.

A voltage increase of 5 times is equivalent to a power increase of 14 dB.  20 x log(5) = 14  The note must be related to the difference between a 0-10 scale and a 0-50 scale.

As Ace mentioned, keep the voltage at 12-14V when using automobile light bulbs.

Thanks again, everyone.

My track circuits have multiple feed wires ~ about every 10 or so feet or 5-6 track sectional joints, and while I am testing in-between feeder wires, I wonder if my voltage test is accurate?

I picked up some 14 gauge wire at Lowes yesterday...it seems like overkill but I needed additional wire anyway and will use it for the remaining long distance hookups. I still find it incredible that 16 gauge is not adequate for the relatively low voltages and currents in electric trains. I look at the tiny wires in the trains, buildings, and transformers themselves - they can't be more than 22 gauge.

Paul,

I tried measuring current (at a fixed point) on my layout while a train was running around it and the meter reading constantly went up and down as the train went around.  Made it impossible to get an accurate reading.

I moved the meter probes from the location I was trying to use and inserted them in between my PH 180 and TIU and got stable results.

When I converted to battery power and removed the middle rail I found a couple of joints where I had "forgotten" to insert a track pin.  I don't know if this had any impact on meter readings but it did explain why I was having power issues in a certain area.

But I was testing the current draw of my can motors more than consistency of track power.

I used the OGR 16 gauge wire for my feeders and found that to be satisfactory.

My experience is that you don't need a lot of extra track feeds if the rail joints are low resistance. I have a 90-foot circuit of tubular 3-rail around my room with only one feed point because it is not convenient to run extra wires across the room. The rails themselves are good conductors if high-resistance rail joints are identified and corrected with the method I described previously.

Ace, that's interesting that you only had to use one feed for 90 ft. of track circle...do you run command - DCS and Legacy or conventional, and what gauge wire did you use? Also, had did you correct poor track connections (the high resistance ones) - just by tightening the adjoining track sections?

unless you keep your layout close to absolute zero, ANY wire in ANY gauge is going to have some intrinsic resistance and thus will drop a fixed amount of voltage for a specific current load over a consistent  length.  since i don't run any trains anywhere close to the full voltage output of a transformer (if you pump > 12 volts into a Marx engine, it won't hold the first curve it hits), it makes no difference if wire i use drops one or two volts (though at the current Marx motors use, it's more like ¼ -  ½V) as long as the drop is consistent around the entire layout.

the only voltage drop that would, and has ever, concerned me is where a specific spot on the layout drops more voltage than the rest of the track.  then you have a problem.  why anyone concerns themselves when a meter reading at the transformer output is a bit higher than the track voltage is beyond me.

but then i promised to shut up about this topic.
think i'll go wind up some clockworks and calm down.

smiles...gary

Paul Kallus posted:

Ace, that's interesting that you only had to use one feed for 90 ft. of track circle...do you run command - DCS and Legacy or conventional, and what gauge wire did you use? Also, had did you correct poor track connections (the high resistance ones) - just by tightening the adjoining track sections?

I run conventional. I have about 6 feet of 12-gauge wire from transformer to track. Where I had high-resistance rail joints that couldn't be readily fixed by dis-assembly and cleaning and tightening, I soldered a short piece of solid copper wire across the base web of the rails. It wasn't convenient to run additional track feeds because it's a room-perimeter floor layout and additional feeders would have had to go under or across the floor. There is a second 90-foot circuit that has one additional feed partway across the room for balloon and wye tracks.

I soldered maybe 40+ rail joints on 200+ feet of track, mostly on old rusty O72 curves that needed a lot of clean-up. Cleaner newer tubular rail generally makes zero-resistance joints if the pins are tight.

Sorry to thread ressurrect - but I'm wondering something.

Has anyone tried using conductive foil tape to bridge the weak connections on Fastrack? 

https://www.stewmac.com/Pickup...ive_Copper_Tape.html

I work on Guitars as another side hobby, and was just thinking how that might work...  I'll give it a shot this evening as I have a couple of slowdown spots on my layout.

Escher posted:

Sorry to thread ressurrect - but I'm wondering something.

Has anyone tried using conductive foil tape to bridge the weak connections on Fastrack? 

https://www.stewmac.com/Pickup...ive_Copper_Tape.html

 

I work on Guitars as another side hobby, and was just thinking how that might work...  I'll give it a shot this evening as I have a couple of slowdown spots on my layout.

Sometime back there was a thread with this issue in it. IIRC the concern was the amperage load on the foil and if it would "burst into flames" or something like that.

Hmmm....some quick google-fu shows the 3M datasheet but it has no data on properties other than sheilding and the adhesive resistance... Guess I'll be the guinea pig..

Here's the data-sheet:

http://multimedia.3m.com/mws/m...ductive-adhesive.pdf

A bit more reading and math...  The foil is 1/4" (6.35mm) X .032mm thick. - CSA = .2032 mm^2.

From the AGW tables:

https://www.powerstream.com/Wire_Size.htm

That is approx 24AWG - and in free air for chassis wiring can handle 3.5amps.

To be safe, I'll stack two foil layers as I read the transformers can put out 4-6 amps.