Okay - for starters, I apologize for the newbie question (although I've been playing with trains for a few years now). I've done a few searches on this forum and seem to be going in circles, but have learned a tremendous amount -- THANK YOU!
I am rebuilding a smallish layout (5x10' with a 4'x5' extension and two levels) for me and my kids. Our last one just sort of "grew" after my son received a starter set 5 years ago and now we want to do it "right." It will have three loops and be run by three transformers.
Loop A run by a CW-80 (I think I know the problems with this transformer and I have replaced a few of these already).
Loop B will also be run by a 2nd CW-80 and will be connected to Loop A. They will be isolated (break in center rail), but I understand there are still some concerns with this set-up. I wasn't able to figure it out though.
Loop C will be its own loop and run by an MTH Z1000. We have a train with PS2 and I know it doesn't play nice with the CW-80s.
Question #1: How do I connect loop A and loop B safely and still run with separate transformers?
Question #2: I lost the sound board in one of the Lionel tenders to what I'm guessing was a voltage spike so I am now going to add TVS's to the track. What size will be sufficient for these transformers? All of the posts I've read deal with larger transformers, but will a 1.5KE36CA be sufficient?
Question #3: I use terminal strips to direct the power (i.e., power and ground to a terminal block and out to the track from there. Can I just put the TVS on each of the terminal strips- one side to the power hook up and one side to the ground hookup?
Question #4: I'm using primarily 16awg wiring with some 18awg. What size (amp?) and kind (magnetic? thermal?) breaker do I need? Is a fuse better? if so what kind and size?
I know these topics have been beaten to death, so a re-direct to previous posts would be fine.
Thanks in advancePhilip
Answer #1: There is some reason to hope that, because of the particular output circuit of the CW80, that you might be okay with nothing more than a plastic pin in the center rail between loops. I would not give you any guarantee, however, since the complete design is proprietary.
A conventional block control setup will work and is not that complicated. Isolate the center rails of the two blocks as you would in any case. Connect one block's center rail to the common terminal of an SPDT switch. Connect the other block's center rail to the common terminal of a second SPDT switch. Connect one of the other terminals of each switch to the A terminal of one CW80. Connect the other terminal of each switch to the A terminal of the other CW80.
(Connect the U terminals of the CW80s to the outside rails. This assumes that you have the revised version of the CW80.)
Now each of the SPDT switches determines which CW80 powers one of the blocks. When you plan to run between blocks, connect both of the blocks to the same CW80. After you have crossed the gap, you can reassign the two blocks as you wish.
Notice that you are not limited to two blocks with this scheme, even though you have only two transformers. You can subdivide your blocks at the expense of only one additional switch for each new block. This can help with maneuvering two or more trains between the blocks. Center-off SPDT switches give you the additional flexibility of shutting off blocks completely.
Answer #2: That is a pretty good choice for most transformers. The voltage selection is made as follows: Determine the peak voltage that your transformer can put out. For a sinusoidal output, this is 1.414 times the RMS voltage, which is how the output voltage is usually described. For the CW80, the waveform is based on a sinusoidal voltage of 20 volts RMS; so use 28.3 volts for the peak. Look up the TVS that you need on the Vishay data sheet. It is one with at least that "stand-off" voltage:
http://www.vishay.com/docs/88301/15ke.pdf
Be sure that the part that you get has a "C" after the voltage, indicating that it is bidirectional.
Answer #3: Yes.
Answer #4: Sixteen AWG is safe for about 10 amperes. Eighteen AWG is safe for about 7 amperes. So that is where your overcurrent protection should be. However, if your transformers already include protection at no higher current than that on each individual output, you shouldn't need anything else. Adding external circuit breakers or fuses is usually necessary for safety when using multiple output conventional transformers, like most of those made by Lionel in the postwar period.
Bob Nelson
to bob nelson: can you please tell me where to purchase a vishey 1.5ke36ca. i find only distributors that want to sell in 1000 or more lots. i only want 2-3. thank you, rj conklin.
I have always found Mouser willing to sell components in small quantities. Their part number is 625-1.5KE36CA-E3 and the their price for one is 68 cents.
http://www.mouser.com/
thank you bob!
Bob,
Thanks for the info. I now understand the concept of crossing into two blocks using two transformers. I do have two revised CW-80's so the hook up you described should be fine. We had it connected without the switch and I was always a bit worried when a loco or car straddled the break in the center rail -even when in phase and at the same output.
Will the 1.5KE36CA provide the necessary protection? I'm guessing the spike I am trying to protect against is greater than 36 volts but will a 30 volt do damage to the electronics?
Thanks again for your help.
Philip
I doubt it. There's probably little chance of damage below about 50 peak volts, which corresponds to about 35 volts RMS.
Thanks again Bob. With regard to the SPDT switches - what should the current rating be? I've taken a look at mouser.com but still trying to get the hang of the site.
Thanks
I would say at least 5 amperes, but 10 would be better. With switches, the current rating usually goes up when the voltage goes down; so many switches are rated for 125 volts and 250 volts, with a considerably higher current rating at the lower voltage. At toy-train voltages, it is reasonable to expect that a switch can handle a little more current yet.
Switches meant for automobiles are usually rated at 12 volts. But DC is so much harder on contacts than AC that whatever DC current rating the switch has is certainly okay at twice that AC voltage.
By the way, when you arrange block switches on your control panel or whatever, consider mounting them sideways, with the handles moving left-right. If your transformers are side-by-side, that can make it very easy to know which switch position does what.
Bob - once again, thanks. And I like the idea of mounting the switches sideways.
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