This is a technical problem and it is hard to accept this matter and if anyone is interested; i will post a photo of the area and a circuit diagram. Two different problems are involved and so is AC current on MTS.
I am doing some block wiring and isolating various sections of my railway prior to connecting up an LGB detection module. This involves putting in two isolated sections 3 m long on the blue rail trailing sides of switch S10l. The direct trail goes on around the circuit in area 2 and the divert side goes via about 8 m track to a reversing loop module in area 1. I am using a supplementary switch on S10 to do the switching of power and the isolating.
On direct i have 21V AC on facing, same on direct trailing and 1.6 V on the divert side.
On divert i have 0V on direct trailing, 14 V on divert and 14 V on facing!
Why the big voltage drop and why the 1.6 V on divert, it should have been zero?
By sheer luck i found a high resistance soldered joint about 10 m away on the facing side blue rail and when i fixed that i fixed the voltage drop, i suspect i have always had this problem and didn't know it and the isolating and the 1.5 V problem made it stand out and detectable.
I am still concerned about the 1.5 V as i believe it will affect the detection modules performance; in that it will think it has a loco in it all the time.
I have two Hillman insulating clamps on the blue side one at the switch and also at the other 3 m mark. I measured the resistance of each one in situ and i got about 2.4 k ohms each so, this is ok. I removed all clamps and so i now have a piece of track completely isolated at one end and only connected to the other part of the track on the red rail side. I get 1.6 V across the far section and 2 V across the near section. The far section is connected to the reversing loop which should have no power to it at all.
If anyone told me about something like this i wouldnt have believed them You just can't have a piece of isolated track with 2 V on it, yet i have!
So i came up with the idea that if it could not be electrical, it might be electro magnetic.
This piece of track has been down for about 4 months and if i did not do this exercise, i might never have known. How is it different to the rest of my layout well my wife came up with the idea that the only thing we have done that is different, is we have used some granite chips we had left over, as ballast under the fines. I see granite does have ferrite pyrites in it.
I also have a 20 V AC wire running right along side this track to run switches and signals, so i thought it might be forming a giant transformer and i am getting an induced voltage, so I disconnected the AC at the transformer and it had a significant drop say down to 1.1 V but it was still there. So some induction is occuring and the only thought that i have is that DCC signal from the central station was somehow inducing itself from one leg to the other a bit like a radio transmitter and reciever. When i disconnect the MTS att the central station it foes.
Any ideas?
Hopefully Ian
Rgds ian
Ian:
What you might be seeing is 'float voltage'. In a given environment, especially the way you describe yours, it certainly isn't impossible to have 'induced EMF'. In plain words, 'stray electric current (or Voltage)'. Try hooking a milliammeter (that's one that reads in .001 amps and up, and see if there's any current flow. You might get a spike, then nothing. That tells you you've got induced EMF. You can think of your entire line of track as a big conductor just sucking up everything from the local radio station's emissions to a powerline's magnetic field somewhere. The earth's magnetic field is a (vanishingly) faint consideration, too, unless you happen to be sitting over a mass-con of iron ore in the ground. Most likely, you've got a combination of 'gremlins'. I'm speaking from some years as an avionics field service engineer.
If, on the other hand, your ammeter reads a steady current flow, then yeah, you've got a problem with 'leakage' somewhere, and you've got to track it down (pun!<g>) and fix it.
Hope this helps.
Les Whitaker
KS:
Once you determine (or decide) the problem is 'float voltage' all you have to do is ground the offending rail. Drive a spike in the ground and connect a wire.
Les W.
Well gentlemen, thank you and i am pleased, very pleased and impressed with what you have said.
Les, it is the MTS system and/ or the transformer running it, as when i disconnect them it stops. I have tried to read the current already and i only have a 10 A digital meter and it isn't enough to register on that, in either section.
Incidentally the 2V bit has risen to 6V.
I have done further tests and ruled out interference from the reversing loop.
Kevin, i have always admired you (an Aussie joke) and now i know why, because what you have said is exactly what i have come to conclude myself.
A few things along this track to do with ballast, some Aussie quarry fines are magnetic i have a magnetic spirit level and granules stick to it all the time. But if this was the culprit i would have this problem all over and i do not htink that i do!
I consulted my step son who has done geology as a subject, at the Uni of NSW and he reckons granite here in Australia is not magnetic. But the internet tells me otherwise of granite in general especially from China. Evidentally some people want it and others do not, there is even a company that will advise you on how to handle ferrouse pirites in granite. I also have the idea that the grayer the granite the more pirites it has and this stuff is very grey and shows some pink when wet. Iam going to find out if where the granite comes from; if they will tell the truth, it could well be cheap Chinese granite.
Action at this time; I am convinced it is what you said Kev, its a combination of ballasts, the magnetic fines with the ferrous pirites in the granite that is doing it. If the LGB detection module works as it is, i will forget about it. if it doesn't i will pull the whole thing up do some experiments and re lay the track about 8 m of it.
Well done fellas.
Gentleman? Gee, I'm at last gettin' some respeck.
If you unhook one of those fancy items at a time, it might tell you which one's 'leaking' voltage. If you can't do that, consider that your MTS (whatever that is) requires a small 'tickler' voltage to tell the unit 'I'm the controller, I'm here, be ready for my commands." In other words, the receiver unit needs to be 'online' all the time and needs a very small voltage to keep it up. I dunno, just guessing.
Yeah mate you did better first time; ive done all that; and i don't think anything like that is causing it, because i have isolated everything, its got to be what Kevin said, i think.
In any case i'll keep you informed as i progress, i am retired with time to really look into it. But its so hot here i can only start work at 4pm each day.
Rgds Ian
Ian,
Do you mean to say that this particular section of track, even though it is not connected to any external power source, has 2 volts present? Is the voltage rail-to-rail or rail to ground?
Walt
Walt i am glad you have waded into this, i know a bit about your technical backgrownd and it will help i think.
Consider a piece of track, it has 4 ends, three of which are islolated, so in fact i have two pieces of track. the blue wire is connected to the first section and also bewteen the two pieces of track. The near section had 2 V between the rails and the far section had 1.5 between the rails. today the 2V has gone up to 6V.
I can supply a circuit diagram and a photo if it will help.
If i disconnect the AC from a wire that is running alongside, it reduces by about 0.5 V. If i disconnect the MTS it goes away all together.
I think Kevin hit the nail on the head, i think it is the ballast which is providing a core if you like and the whole thing has become a weird big transformer. I sold transformers for a living for 18 years.
What do you think Walt, i will be glad to see it. Have a good read about what Kevin and I have said.
I know very little indeed about MTS in particular and DCC in general so a circuit diagram would help me out a lot. Please e-mail me at ussamaru@yahoo.com.
The only problem I have right now with the transformer analogy is that you're reading the low impedence primary of the transformer which is being sourced from a zero voltage device.
Thanks
Yes Walt, you a quite right and that what makes it all the more confusing. Possibly the idea of RF being involved may be a way to view things.
Say the blue track, which is connected to MTS is acting some how like a transmitter and the ballast is enhancing the transfer of energy to the red track. This would generate a potential difference between the two and the closer one to the source has a much higher voltage. The fact that we can't really get a current reading, would indicate how tenuous this matter is.
I realise i am clutching at straws but it is possible, unlikely but wildly possible.
Keven said it has happened before but very rarely and it is to do with the combination of ballast and that is all that i can think of that is differen in this situation from the rest of my layout..
Circuit diagram and photo coming up soon.
Our techie would for starters connect a large enough resistor (55 Ohm, 5 watt to try it out) across the output of the MTS unit.
That should absorb whatever stray voltage there is by creating a load which doesn't allow "floating voltages".
Worked on many similar situations in the past.
ER
Walt, I'm sorry, its been a while since i have had a precise technical conversation with anyone.
I did not mean RF, i meant a radio like emission.
Elisabeth i think your man is quite wrong but i will try it out. If it is to do with the MTS unit why aren't the other 190 m affected; why only these 8 metres?
I have a freind who is a retired Television Engineer and he is bringing over a meter to measure any emissions that may be around and his advice is at this stage is to ground the two offending sections.
I still reckon that Kevin is correct, if that is the case what would your solution do?
Gentllemen;
Inputs from younger people will be greatly appreciated, however we have 2 grandfathers working on this in the background, and we will keep you informed as to any progress.
Ray
I don't think what you have said is emtirely correct but i also don't think it is entirely incorrect either.
I am pretty sure one way or the other the ballast is to blame and i don't think it is an electronic problem, more elctro magnetic.
Anyway mate thanks for your offering and hopefully it will keep us off the streets for a while,.
I am more bemused by this matter than worried.
I share this to confirm the conductivity of ballast:
I operate loops of track containing electrically separated (one rail) blocks that are controlled using Dallee Track Detectors (relays activated by current flowing through a sensing coil). A locomotive or a track-powered lighted car shifts the relay feeding the following block so that a lowered voltage goes to the isolated rail. The system has proven rugged and reliable, enabling me to automatically run two trains on each 100 foot loop.
Recently the one block, after being in place for eight years, ceased to operate. I checked wiring, the insulated rail joiners, the detectors involved -- and found nothing amiss. I then lifted the track from its bed (it was very well settled) and found that mulch from an adjacent bed had worked its way into the ballast stones and had actually matted itself across the underside of the track so that I had to knock it free with a screwdriver. I enriched the ballast, put down the cleaned track, and found that normal operation was restored.
I have never checked to determine what sort of voltage draw is required to activate the Dallee detector, but my filthy ballast was conductive enough, even when dry, to imitate a light bulb.
Arthur
Arthur mate; that was terrific that you have tolfd me this, i gives me hope tp carry on, thanks.
I would like to contact Dallee electroniocs, as i am into detection systems and automation do you have an email contact for them or better still a decent website.
Thanks again; Ian
This matter has taken a turn for the better, i had a friend come over with a sensitive analogue meter and we could only get about 3 ma out of it and my device neeeds 15 ma to cause it to operate. So i should be running on the detection module tomorrow or the next day and we will see how it pans out.
The detection module situation is not going well, i think i need abigger or better brain.
However the spurious voltages do not seem to tbe worrying the detection module. it seems to be working ok, so i guess this posting is closed. Thanks for all the help.
Regards ian
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