Realizing that there is considerable discussion previous on this subject but I guess I am visual person and there were no pix. So can anyone give me a site to show how to wire the DPDT toggles to control a turnaround wye. I am getting confused not knowing which wire to attach where on the switches and which wire goes to which rail. thanks in advance for any and all your responses.
John
Detroit, Woodbridge and Birmingham
IIRC, the center leads go to the track and either the top or bottom pair of leads goes to the power pack. There is also an X between the top right/bottom left (and vice versa).
jj:
I am showing a balloon loop. For a wye, just pick one leg and consider that the reversing section.
Centre terminals get input power from the DCC controller or bus.
One of the other two pairs, flip a coin, gets wired to the loop or reversing section of the wye.
The other pair of terminals also services that same section of track, but with the wires going to the opposite side of the switch. That way, whatever way the toggle is thrown will provide you the track power you need for that reversing section since the outer two terminals are going to that track, but depending on which side the toggle is flipped to, the “polarity” (of sorts) changes.
Sorry, I should have saved a diagram I drew some months ago and posted. If you wish, I will draw a new one and scan it.
This raises a question I have regarding wiring a tortoise with a dpdt toggle, which is performing the same function as it’s use in a reversing loop. The instruction that come with the tortoise show the power coming into the upper terminals then a X to the lower terminals, and the center terminals go to the tortiose. What am I missing?
The actual position of the terminals on a DPDT can differ. You really want to have an Ohmeter or even just a continuity tester (light bulb and battery) to see which terminals are which. The difference in terminal positions can make two drawings of the same functionality look different.
EDIT:
I just looked at the posted pic more carefully, and I see why you are confused. It is a bit different way of wiring it, but if you chase it through, you’ll see that the end result is the same, it’s just a matter of whether the cross in the power is before or after the switch.
Here is a electronic diagram of a DPDT switch. Whether you use the center as an input or output is up to you. As you can see by the diagram that when the toggle is set left positive is to positive and negative it to negative giving normal polarity. When switched to the right positive is to negative and negative is to positive giving you a reverse polarity. Now the reason for the X on the switch is to save you running 2 sets of wires to or from what you are controlling. So instead of 3 pairs of wires you are only dealing with 2.
Thanks for the input. In the initial diagram wouldn’t the blue wires go to the “most of the tracks” and the black wires go to the reversing section? It looks like the way it is diagramed the toggle will change the polarity on the larger part of the layout and the polarity of the reversing section will remain the same.
This may be the way he does it. But I would agree and do it the same as you. The loop would be the part I would want to actually switch the polarity on for the reverse loop or wye in your case.
ff:
Yes, exactly. This is the key to wiring a reversing section with DC power (or 2-rail analog AC, for that matter). When the East-West switch is in the “inbound into the loop” position, the loop and the main should have the same polarity. The main is switched while the train is in the loop. If you were to switch the loop itself, you’d have to stop, switch the loop, then throw the power pack’s reversing switch before proceeding.
Switching the main also works with DCC systems. However, so does switching the loop, as Selector mentions. Since power is picked up as AC and rectified onboard of the locomotive, the polarity to its DC circuits never changes.
The key here is that when you switch the main loop you are switching the main loop for just that cab. So you never have to change the loco direction. As has been pointed out, with DCC it doesn’t matter so much which you switch, you just want to set things up so that you won’t be entering and exiting at the same time.
The NMRA has a nice article describing how to wire a wye at “nmra.org.”
Just access their section called: “Introduction to Model Railroading” and your questions should be answered. They also have nice visual diagrams that will be helpful to you.
Good Luck,
Wayne
I just want to thank you all for your help. It just goes to show you that Model Railroading attracts only the bestest folks. Thanks again for all your help. As soon as I can get back down to the railroad (my daughter is getting maried in two weeks) I can start to wire it up.
jj:
The bestest and the vestest. Congrats on your daughter’s upcoming marriage. The year I got married was the same year in which Frau Autobus’ two sisters got married. That was quite $ome year for my in-laws, but a good time was had by all.
N.B. Be sure to invite all the neighbors to the reception, if you plan to have a friend’s band in the backyard.