Polarity is relative so common rail circuits work with two or more sources. One doesn't care what the other's polarity is. However, if you have two speed controllers off one transformer/rectifier, then you have to have both rails insulated and feed both rails in each block. Common rail is more convenient and less expensive. If the adapter for each of those Medvend controllers plugs into an AC outlet, you should be able to use common rail. Doug
So are you saying each throttle needs its own power supply? That makes sense, as the schematic I used (attached) indicates both cabs plug in separately. I just figured I could condense the wiring a bit. I guess what I don't understand is why I can't splice the input. However, the diagram also shows the the two cabs sharing a common rail wire. You're saying while each of my throttles need a separate power supply, I can splice the wires together on the output and be just fine? Each diagram in my book also shows only one common rail connection, instead of the two I laid out. Was this overkill on my part? I'm sorry for my confusion. Just want to make sure I get this right. Thanks again! -Josh
If you use separate power supplies, a common rail can pass one leg of each with no major problems, regardless of polarity. But if you use one power supply, and two cabs that can reverse the polarity, then you either run both trains the same direction at all times, or you don't have a common rail at all, or you short your power supply out.
Makes PERFECT sense. I will use two power supplies. That sounds more manageable than wiring each block separately and running them all through a selector. Everything I just read about two track wiring seems overly complicated for my lack of know-how. This schematic looks ok now? I'm thinking 18 gauge wire for the bus a 20 for the feeders. Does that sounds right? Last question, I promise: How come the output common wires can connect, but not the input? Or is this overly complicated to explain on this forum? If so, don't worry about it. Attached also is what my layout came to look like in case you were interested. My original plan wasn't feasible when I brought it to life, but I kinda like this better! I'll start a new thread once things really get going in case anyone else is interested in my progress. Then I can get off this embarrassingly long wiring thread. It's starting to take shape!
Don't worry about the number of questions. That's what we're here for. Are the power supplies for those controllers wall-wart types (the ones that plug right into a wall outlet and hang there?) Regardless, we would have to see a schematic of everything to determine if you could just use one power supply (AC adapter) and still use common rail. Two supplies is better anyway so you have greater current handling for each speed controller. Your wire gauges are fine. 18 and 20. Doug
Your wiring looks to be a copy of Atlas wiring, using their products. for modern Z I do not like the idea of a single common rail. I prefer to have both rails to be switched and it makes it better for reversing locos, and today's throttles or cabs for Z scale are not designed for common rail , this was possible with older transformer based controllers where they were tied to the household AC, and had a ground terminal, that tied them to the same ground potential. today's wall wart controllers designed for Z, are isolated from household AC so the common rail approach is not a good idea, Ground loops and back feeding will kill modern Z controllers. As for switches you can use any 1 amp or half amp DPDT switch (DPDT = double pole double throw) and I prefer one with a a center off position). this type of switch allows you to have one switch per block with center off and cab A to left and cab B to right. I would then turn the turnout lead near your number 2 on your drawing into my lead to the yard parallel to the inside loop main so you can do switching without tying up the main, and that would be block no 3 outside main would be block 1 and inside main as block 2 the double cross over, I am not inclined to go with your block 4. In my plan To traverse the cross over blocks 1 and 2 have to be switched to the same cab and then you can proceed across the cross over, once through the cross over you can return to one cab per loop, or one to a loop and one to the yard . crossing into the yard turn blocks 2 and 3, should be switched to the same cab, to go from inside loop to the yard, If you create block 4 then to traverse the cross over then blocks 1,2,&4 have to be selected to the same cab. Connecting or wiring your switch the center contacts go to your track and the outside poles go to your cabs, on this type of switch you need to solder the wires to the terminals on the mini 1 amp type the larger 5 amp type some have screw terminals, this type of wring is suitable for DCC or DC track power.
Have you thought of DCC (Digital Command Control) were you control each of the engines not the track. My layout is L shaped approximately 8' x 8' N-scale. I don't have my bus wiring install yet, just the wires hanging down underneath from the track, about every 3 feet.. I have my MRC Prodigy Advance Squared system connected to two wires with alligator clips. I can run the whole layout, duel tracks. I had 6 trains going at the same time, just to see if the system would handle it. Had no problem until I let one train run into another train going in the same direction. Just an idea. I know its more expensive but a lot more fun.
Yes, I plan on buying something like this to power the tracks. I then plan on connecting it to this: http://zscaletrack.com/AN-1-C. The adapters aren't expensive, so I can easily buy two if you think that's the best route. There's a comment a few up from Garth-H saying I shouldn't do standard DC for Z scale. Your thoughts?
Hi Garth, Thank you for the input. I'm afraid I don't quite understand your second paragraph, as I'm still just trying to figure out how to power the rails. At the moment, I'm going to keep my turnouts manual. I'm using MTL track, so I can add the remote switches later. With regard to your comments about common rail wiring, though, are you saying even when scaled down the same concept cannot work? I'm only using no more than 10V and 20 gauge wire to connect things. Are you saying I should insulate both rails for each block and run feeder wires from each throttle to each track in every block? This is the type of throttle I am using: http://zscaletrack.com/AN-1-C. Does the below image lay out what you're talking about?
What i said was you are using wiring diagrams from early days of Atlas and it is old technology for your wiring from a time when all power packs or controllers were transformer based and tied to household AC with three wire cord and plug. today's controllers for Z are not from this group in general, But they are for HO from Atlas. Modern Z scale controllers use electronics to produce DC and are isolated from household AC. The wall wart converts high voltage AC to low voltage DC that is fed to you controller, so you have no common ground across two controllers, so common rail ground is not recommended.
Great and I was a Ham years ago in the seventies, too. My call was WB0WXZ. My first Treble-O-Lectric was a set from Montgomery Ward. Doug
So are you saying the new diagram I drew above won't work either? I didn't draw the track, but basically each block is fully insulated (both + and - rails), with only the negative running though a selector. If I shouldn't use the old Atlas selector, what do you recommend to use in order to control my blocks? Is my track design too complicated to wire? Getting very confused now. Starting to get concerned I bit off more than I can handle with this project.
I don't think he likes those old Atlas selectors. I know I never used the things. Most of us are nervous about answering your questions because few of us run more than one circuit at a time through one wire, or one rail. We generally insulate both rails between blocks, and eliminate possible problems. This requires the use of DPDT switches with an off position. That stands for double pole double throw. The Atlas selectors are single pole double throw (SPDT) center off, meaning they allow you to connect one rail to one side of either of two power packs, or disconnect from both. A DPDT with center off switch completes two circuits to two rails at the same time. They don't add a lot of difficulty. With what you have, you connect one power pack lead to one rail, the other to the switches, and the switches to the other rail. With DPDT switches, you run both wires from the power pack to each switch, and both wires from each switch to each block of track.
Now THIS makes sense. However, the AN-1-C throttle I plan on using already has a DPDT on it for direction. Would this, then, turn it into merely an on/off switch? Would I just use the other DPDT's for each block to control direction? I guess my main question is why can't the DC common rail wiring work with Z scale if the voltage is scaled down properly?
No. The DPDT on the throttle has power in to, on most toggles or sliders, the center lugs on the back. Selecting one position on the switch sends + to the left output wire and - to the right wire. Selecting the other position sends - to the left wire and + to the right wire. With block controls, you don't wire the source of power to the middle lugs. You wire those to the track. You wire the two power packs to the other lugs, so moving the switch to one position connects the track to one power source, and moving the switch to the other position connects to the other power pack. Which way the train goes still depends on the direction switch on the power pack. Your block control switches just determines which power pack is connected to the track. You do have to take care that all the block switches are wired with the same polarity, or when the locomotive tries to run from one block to the other everything will short out. Be methodical--at first be very methodical. Test each section before you solder connections. If you wire it so a train goes clockwise when the power pack A direction switch is slid to the left, and when the power pack B direction switch is slid to the right, you'll find operating the thing to be counter-intuitive and difficult.
Does this schematic layout what you are explaining? I feel like something just clicked inside my head and all is clear as day. No cross-wiring needed on the DPDT, right? I kept finding YouTube videos where they did that and it didn't add up. This seems very straight forward and easily managed by a novice like me.
It shows how to do it wrong, for some reason. It shows the polarity reversed on half of the power pack connections. Perfect!
