A few newbie questions

[lionelsoni]

Yes.  The TVS goes in parallel with the track.  For example, if you are using a lockon, the wires from the transformer go to the two lockon terminals as usual.  And each lead of the TVS also goes to one of the lockon terminals (if you want to mount the TVS at the lockon).

[johnandjulie13]

Hello Bob:

Excuse my ignorance, but when you say "across the wires", does that mean I can connect the TVS to the two terminals?

Regards,

John O

[lionelsoni]

That's right, across the wires.  The "CA" at the end of the part number (as opposed to just "A") denotes the bidirectional version, which is what you want for AC voltage.  It is completely symmetrical, so orientation doesn't matter.  Inside the locomotive is ideal, since it protects from any excess voltage that might arise somehow between the layout wiring and the wheels, although this is pretty unlikely.

[trestrainfan]

Thanks for the additional explanation. By coincidence, there is a thread on the OGR forum about circuit protection, and they are also discussing TVS protection. It sounds like you just solder it in between the power and common wires? Do the TVS units have a specific orientation? Does one end specifically attach to the power wire? In the other thread, some of the posters use a number of them even placing them into locomotives.

[lionelsoni]

A transient voltage suppressor (TVS) is a special zener diode designed to be placed across a supply line to absorb large amounts of power for very short times. The unidirectional ones are simple zeners and are meant for use with DC. For AC you need a bidirectional TVS, which is like two zener diodes in series, but pointed in opposite directions. The voltage rating has to be higher than the peak voltage of the sinusoidal AC waveform, which is 141 percent of the nominal (root-mean-square) voltage.

You can get them from electronics parts houses like Mouser and Digikey.  The part to look for is 1.5KExxCA, where "xx" is the voltage rating.  For example, if your transformer puts out 18 volts RMS, you need at least 1.5KE30CA.  Here is the manufacturer's data sheet:

http://www.st.com/stonline/books/pdf/docs/2913.pdf

The number to look at is the "minimum standoff voltage" or VRM, which should be at least 1.414 (square-root of 2) times your RMS voltage.

[trestrainfan]

Thanks for the welcome and the detailed replies, particularly with the switch radius explanation with diagrams.

Regarding the circuit protecton. I'm not familiar with a TVS. If I understand correctly, it is a surge protector that you use in comjunction with circuit breaker or fuse protections? Is it like this?

http://www.scottsodds-n-ends.com/products.htm

 Someone mentioned the company in a post. Thanks for your help.

[lionelsoni]

I have trouble with the idea that the best way to protect electronic locomotives is to have faster circuit breakers or fuses. This is not to say that circuit breakers and fuses shouldn't be used, just that they do not address the problem directly.

Unless it has already failed, an electronic locomotive can be counted on not to draw an excessive current suddenly. Sudden fault currents will almost certainly be drawn by something else, like a short circuit caused by a derailment. The effect on the locomotive will be that its voltage suddenly goes to zero, or close to it. This is not harmful. What might be harmful is that, when the short circuit is cleared, there may be a high-voltage pulse from the inductance of the transformer's secondary winding.

Since a typical short circuit comes and goes at first, a fast circuit breaker or fuse might well prevent the high-voltage pulse if it can open the circuit before the short circuit clears the first time. A more direct and more reliable approach would be to suppress the pulse, as with a TVS, leaving the circuit breaker to protect the transformer and wiring, which is what it is best at.

[Roger Bielen]

testrainfan - Welcome to the forum.

See the e-mail I sent you.  I'll be there 12 to 7 today.

[Birds]

Welcome to the forum! 

 

I'll chip in about the curves and switches.  I can't speak to TMCC as I don't use it.

Your main line and passing lines only need to be far enough apart so that the engines and cars don't hit each other as they pass.  One normally doesn't have to worry about it because in general the switches don't create a situation where the tracks are too close together.  So just buy your switches and hook them up.

The curves one decides to use depends on the space one has, the curve requirements of the engines and cars owned, as well as the look one wants.

I run traditional sized trains that require either O-27 or O-31 curves.  If some of my engines require a minimum of O-31 curves, then I know they won't work on O-27 curves.  Therefore my layout has to have at least one loop of O-31 curves for those O-31 sized trains to work.  All the O-27 capable engines and cars will negotiate the O-31 cuves without a problem.  So in a case like this someone may go with all O-31 and not use O-27 because they can run all their equipment everywhere on the layout.

I run a 6' x 14' layout.  I can fit a circle of O-54 in that 6' depth.  A circle of O-72 does not fit.  I shared earlier that all my trains will work with O-31 curves.  So the curves I can choose between are: O-31, O-42, O-54.

Even though my engines and cars can work with O-31 curves, O-42 and O-54 curves provide a more gentle curve so my shorter trains can be run at faster speeds through them without the trains flying off the track.  They also don't overhang the curves as much as say an O-31 curve because the curve is not as sharp a bend.  These two features appeal to me more than having a ton of track crammed in the area, and since I have the space I decided to take advantage of it.  So I made a layout with two loops: an outside loop using O-54, and an inside loop using O42. 

With switches you can use whatever you want as long as the locomotive and cars can traverse it.  A locomotive and cars with a minimum cuve of O-31 can use switches that are O-31, O-42, O-54, O-72.  A locomotive and car with a minimum curve of O-72 can only use O-72 switches.

The different switches will have a more exaggerated curve coming off of them.  An O-31 switch will have a sharper curve than an O-72 switch.  This changes the appearance of a layout. 

Below is an example of a layout using:

• O-54 curves on the outside loop
• O-42 curves on the inside loop
• O-31 turnouts (switches)

(Click on image to enlarge it) 

 

Below is the same track design but using a different brand of track whose curves are slightly larger (even though they say they are O-54 and O-42) and using O-42 turnouts instead of O-31 turnouts:

The differences are subtle, but they are there.

The O-42 turnouts pulls the sidings closer to the main line, and brings the two loops closer together.

The larger curves requires the two reversing loops inside the inner loop to have more of an "S" look in order to fit. 

Good luck!

Chris 

[trestrainfan]

Hi:
I recently purchased a Lionel Christmas starter set (and the freight and passenger expansion sets) after thinking about it for a few years (rekindles childhood memories  ), and have enjoyed running it. I'd like to expand and be able to run a few TMCC trains at the same time on a Christmas theme layout. I've picked up the Berkshire locomotive from the Chesapeake super freight set to pull the pasenger cars, and the SD90 locomotive from the Canadian Pacific freight set to pull the freight cars (plan on having a number of operating cars). I have the following on order: trainmaster command set, a tpc 400, and a 180 watt powerhouse. All the larger internet order firms seem to be out of these items right now. I'm planning a layout using fastrack, right now now I'm visualizing an elongated dogbone shape with a long passing siding for actuating the operating cars while the other train continues on the main loop.

I've enjoyed reading the forum for a few weeks and decided to join. I've learned a great deal from reading the posts, but still have a bunch of entry level questions.

Is the TMCC direct lockon (6-34120) a good product to use to protect all the electronics? A number of posts mention fast-acting fuses. How does the lockon compare to the fuses? If I end up going the fuse route, are there any tutorials on what to purchase and how to hook them up?

I plan to primarily run TMCC controlled locomotives, do I need to break up the layout into blocks? Is it a good idea to do it anyway so I can turn off power to the siding if I am not using it?

I plan on using fastrack remote switches. I see they come in 36, 48, 60 and 72 versions? How do you decide what size to use? What are the advantages and disadvantages of the different sizes? It seems like the various versions come with extender straight sections, so they all go about the same distance away from the main line. How far apart should the main line and the passing siding be?

Thanks for any help you can provide.