Resistance Testing and Remediation Approaches - Fastrack Layiout

My multimeter - picture

Actually, a much more conclusive test is by passing current through the track and checking for any voltage drop at each track joint.

Find yourself a nice hefty 12-18 volt bulb and connect two alligator clips to it with a foot of wire.  You want a bulb that will draw several amps to be effective.  Pick a spot on the layout and clip the bulb to the track and power it up.  Now, go to each track joint between the power feed and the bulb and check the voltage across the joint.  You should get very little voltage reading there, if you're getting anything from a tenth of a volt or more, you probably need to address that joint.

Exactly what gunrunnerjohn said. Checking resistance of power circuits with an ohmmeter is futile. Put a load on the circuit and check voltage drop.

I can add here that a quicky test under load is simply touch each joint. A joint with any amount of warmth is seeing excessive voltage drop. Follow this up with a meter test as desribed above.

Rod

@Rod Stewart posted:

I can add here that a quicky test under load is simply touch each joint. A joint with any amount of warmth is seeing excessive voltage drop. Follow this up with a meter test as desribed above.

Rod

My FLIR add-on infrared camera module has more than paid for itself finding easily problems like this.

Throw a good load on the track, apply power, not even 10 seconds later, you know, beyond a shadow of doubt anything not up to spec. It's that visible. Look at the table from the top, look at you wiring under- it will blow your mind problems you didn't know about.

Fundamental game changer tool.

Hi Gentleman (GRJ, geysergazer, Rod Stewart, Vern Barry),

Thanks so much for redirecting me to focus on the real possible problem of finding if I have any noteworthy voltage drops, rather than identify one of perhaps multiple possible resistance causes which can be dealt with as needed to address a found voltage drop.

As a novice one clarification request in relation to GRJ's method ...

My track wiring has feeders from bus below up to track connections every three (3) feet across the whole layout. So when I place a bulb load it will be between two feeder points 3 feet apart wherever I am on the layout.

As such when you say "Now, go to each track joint between the power feed and the bulb and check the voltage across the joint" do you mean:

a. between the bulb and to either side of it to the two feeders the bulb sits between, OR

b. between the bulb and the power source transformer ... in my case ZW(L).

Thanks so much!

Ken

If you have track feeders every 3 feet of track, you don't need to worry at all about joint losses IMO.

Where it becomes a problem is for larger loops with perhaps only 2 or 3 power feeds and 6 or more track joints between them. You should be just fine.

For the light bulb method, the bulb would be attached across the track at the farthest point from the feed, or between 2 feeds. Then you would have several joints between the supply and the load, if that makes sense.

And by the way, a surplus automotive headlight bulb makes a great dummy load, with track voltage set to about 12-14VAC. Hope that helps.

Rod

Thanks Rod! Even with the 3 ft apart feeders I plan on testing methodically over the whole layout.

I figure if I find voltage drop areas I will either upgrade the current feeder from 18 AWG wire to 16 AWG or just add a new feeder to the center point of low voltage.

I am so glad I joined OGR before I started building … I have learned so much from you guys- thanks!

- Ken

With power feed wires every three feet there is no need to test for any voltage drops. There won’t be any.

That is considerably closer than you really needed to do. Power feeds every 6 feet would have been fine.

Ken

Save your time and effort on doing all that ohm testing and run some trains.  If you have your trains running with no issues you are good to go.  If poor conduction does not show up, with noticeable slowing down of trains, you do not have problems.  Do not make a problem you do not have.

18 vac will give you more electromotive force or voltage to overcome a few ohms of resistance than the 6-10 vac I have on my conventional control.

Charlie

Yeah, this sounds like a solution looking for a problem.

@Richie C. posted:

Yeah, this sounds like a solution looking for a problem.

Back from York.   Yep, if there are power drops every three feet, I think fooling around testing anything is a fool's errand, I agree, just run trains!

Thanks GRJ. I appreciate the confidence builder … helps me contend with my newbie nerves, even thought it’s just toys!

-Ken