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I am not sure if I have a problem with my theory, my execution or my TIU. I am running a FasTrack loop with a crossing track in the middle. A SuperStreets trolley crosses the crossing track with a FasTrac/SuperStreets crossing. I have one of the outside rails isolated so that when a train is on the crossing track, the isolated rail picks up the ground and operates a relay.

 

When I test it with a multimeter, the isolated track does not have continuity with the other outside track, unless a train is on the crossing track. When a train is on the crossing track a combination of the center rail and the isolated rail produces @18 v AC. When no train is on the crossing track, the same leads show no voltage.

 

I reduce the 18v AC to 5 v DC to operate a 5v relay. The relay switches properly, switching between NC and NO properly when activates with 18+ AC from a small transformer.

 

Then I hook up my TIU and the relay starts chattering, and both the NC and NO posts of the relay seem to be activated. (I imagine they are seeing AC voltage and switching faster then I can measure.)

 

So I put my multitester on the track between the center track and any outside track and get a short reading from my mulitester, with a reading that varies some but levels out at about 8 ohms. This occurs any place on the layout. I found that removing the TIU eliminated the short. When I check voltage on between the isolated rail and the center track, I get s small AC voltage, even though the isolated track in not connected to ground.

 

Does the presence to the TIU make it impossible to use a relay in this fashion? Are these strange reading expected when the TIU is hooked up or do I have a problem with my TIU?

 

Thanks for any suggestions.

 

DIck

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Dick,

 

A wiring diagram would be most helpful. There must be something else that you're doing that's causing your problem.

 

Frankly, I don't understand how simply inserting a TIU between the track and a transformer can cause what you're describing. There's nothing magic about what a TIU does with electricity - it just passes it straight through.

I think I asked too many questions at one time. Has anyone used an isolated ground and a relay with DCS?

 

Barry - I am not good at diagrams. I will try to put something together. Is there any thing in particular I should focus on?

 

PCRR/Dave -- I am running the DCS with a Z-1000. The smaller transformer was used only to test the relay operation. It was not hooked up to the track or DCS.

 

 

I clearly have to do more trouble shooting. Dale -- I am using your diagram. I am using a Radio Shack 5v relay, with a regulating circuit stepping the AC 18v down to DC 5v. Since both you and Barry and Dave all tell me that the TIU should not be causing the problem, I will do more isolating and see what I can come up with.

 

If I put a resistance meter across the A & U terminals of a transformer, should the meter read Open, or should is show some resistance?

Last edited by Dick Richard

Found the problem -- the ground on a Fastrack Remote switch had come loose and was touching the metal on the bottom of the switch. When I properly connected that ground wire, everything worked properly.

 

Barry -- with all respect, the TIU and AC electric in general is magic to me. Lacking the technical expertise of the experts on this board, to me it works because it works. Kind of like an airplane. How the heck does is stay up. But it does, and I fly with only a little trepidation.

 

Thanks for helping me get my focus off the TIU. Once I quit barking up the wrong tree I was able to solve the problem -- and learn a couple of things in the process.

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