Sir James> I hear ya. Gonna stay with one transformer handle for now. Till I build the second level.
Bob> Thank you so much. My small layout is outfitted with the proper size track wire, TV's and fuses for each block. And it still works. LOL. Really, I feel a lot better knowing I took my time with the track work and did the best I could.
It's one of those things like putting a safety valve on a boiler or circuit breakers on your house or doing a high-wire act without a safety net. The boiler may never blow up, the house burn down, nor you fall off the wire. In this case, if you get the voltages set close (and with the same phase and waveform) or the transition is brief (the train doesn't stall) or you don't have any delicate modern electronic locomotives, you can get away with running between transformers (or, even riskier, multiple outputs from the same transformer). But I don't recommend it, especially when there are easy alternatives.
Bob Nelson
Bob is the forum expert so you should follow his advice. But I'd like to say that I have never had a problem moving trains from one transformer circuit to another, using common ground wiring.
"IT's GOOD TO BE THE KING",by Mel Brooks
Charter Member- Tardis Train Crew (TTC) - Detroit3railers- Detroit Historical society Glancy Modular trains- Charter member BTTS
The single-diode trick is a good way to get a substantial 30-percent voltage reduction without making much heat. Unfortunately, it always gives you a 30-percent reduction--not adjustable--and, as you discovered, the result includes a lot of DC. But it is a very handy way to drop the voltage for something like an incandescent lamp (as in a turnout) that doesn't care about waveform but only RMS voltage.
The bridge rectifier trick allows much finer adjustment of the drop and doesn't introduce any DC to fool the whistle-bell circuits. You can of course do the same thing with individual diodes wired in a series-parallel manner; but you would need a fistfull of them.
You asked whether it will get hot. Yes, but not very if you use the big rectifier module I suggested. Radio Shack also sells a 25-ampere unit meant to be mounted on a heat sink; but I don't think you will find that necessary.
You can use the same string of modules for several different blocks if they're all powered by the same transformer output. If necessary, different blocks can be connected to different points on the string of modules to customize the different speed reductions.
No. Connect the + and - terminals of the bridge rectifier to each other but not necessarily to anything else. Then you will have converted the 4-terminal bridge rectifier module into a 3-terminal voltage-dropping module. Disconnect the transformer wire from the center rail of the block where you want the trains to slow down. Connect that transformer wire to one of the ~ terminals and connect the center rail to the other ~ terminal, so that the voltage-dropping module is in series between the transformer and the center rail. That will give you about a volt of reduction in that block.
If you want less reduction (more voltage), connect the center rail to the +- terminals of the module instead. If you want more reduction (less voltage), make a second module and wire it in series with the first module, transformer to first module's first ~, first module's other ~ to second module's first ~. Connect the center rail to any terminal of the string of modules. The farther down the string you put it from the transformer, the lower the track voltage.
Does that make sense?
lionelsoni> Thanks for the lesson.
Just to clarify if you don't mind...
I can hook up the + and - of the bridge rectifier to the + and - of the wires leading to the track in the particular block that I want to slow down. Do they get hot? Cause I would like to mount under layout.
Thanks guys.
Using a second transformer guarantees that there will be a fault current and voltage spikes when the train crosses the block boundaries. Only if you set both transformers exactly to the same voltage will you prevent this from happening; but then there won't be any change in speed either. which defeats your purpose. A passive voltage-dropping element--like a lamp (poor), resistor (okay), or diode array (best)--will slow the train down without causing electrical problems.
You could also use another small transformer and adjust the voltage to fit your needs. You would also need to remember to turn them both off.
Putting lamps in series with the train was one of the early methods used to control speed. The lamps were between the track and the 110- or 220-volt power line--no transformer! Even with a transformer, as you propose, lamps are not so good, since they tend to create more a constant-current source rather than the constant-voltage source that you need. Resistors are better; and an old Lionel rheostat is a reasonable choice and easy to find.
However, the best voltage-dropping element that I know is a string of silicon diode pairs. They will give you a constant voltage. The simplest way to do this is with one or a few bridge-rectifier modules: http://www.radioshack.com/product/index.jsp?productId=2062583 Connect the + and - terminals together. Then use the ~ terminals to wire the module in series with your transformer. You can use the +- junction as an intermediate tap. If you need lower voltage, just add another module in series.
Would like to slow my trains down on a couple of straight a ways. What would be a good method for slowing them down just a little bit while they are in those blocks?
Will adding bulbs or resistors slow the train down in the block, if adjacent blocks do not have bulbs or resistors?
Why? The small layout has a few 180 degree curves on one side which slows the train quite a bit. Sort of like a "W" where the bottom middle of the "W" is an aisle in the middle of the layout. Then on the large straight and passing siding on the opposite side of layout the train flys by.
It is not all that bad as is but thought I would ask. Thanks.
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