I'm in the process of routing my track buss under the layout, however, before I get started I would like some input. I will be using Digitrax DB150 as my command station, also my layout is in the shape of a square, with access in the center. In saying that my ho track will consist of three large ovals each about 30 feet in length. My thoughts were to have the command station on the outter two ovals ( about 60 ft. of track) and the inner oval its own seperate booster (about 30 ft.) also there will be a small yard ajoining the inner oval. Obviously all crossover tracks will be gapped on both rails. Should I run the two seperate busses exactly the way I will run the track? An oval? Suggestions? Thank you. mmr
I would suggest that the shortest route of wire off which your feeders would rise to the various rails is the way to go. I would situate the DB150, and then run twin bus pairs left and right. Drill holes through the wood spacers and joists or end-frame members, just a 1/2" hole, and thread the two wires through those. You needn't close the two loops at the far side of the benchwork...just end them with some safety caps and tuck them out of reach and separated by a couple of inches for safety.
Then, break the insulation where you must and run feeders.
In my case, I would run a bus each way, not touching or closing at the far side, but I would also run subs off the bus and feed each of the three ovals with a tail light bulb in series in the sub. Off of the subs would come the feeders.
I don't understand why you feel the need to use a booster. If you are going to be running maybe 10 engines at once, most/all of them sound, then yeah, maybe one other booster. But if you are a lone wolf, you are unlikely to be running more than two trains at a time, unless you like watching three? Two three-engine trains are easily within the capacity of a DB150. So, if you wire it up so that shorts are managed and you can keep the system alive, I would use districts controlled by light bulbs or circuit breakers.
Crandell
I understand your suggestions for the most, what I'm confused on is " ... districts controlled by light bulbs or circuit breakers." I don't understand how this would be done, if you could explain this a little more in detail. As far as managing the shorts, I will be dedicating a DCS50 (zephyr) to power all my turnouts/switches. Is this what you are referring to?
A short occurs when a metal tire on a rolling item, engine or car, bridges two rails of opposite polarity. Same as crossing the two wires in an outlet. They are dangerous! And they happen to all of us, sometimes once an operating session, sometimes several times.
When your DB150 or booster detects a short, it shuts power to the rails immediately, in a few milliseconds. The idea is to protect everything from the heat produced by the power supply's maximum rated output in amperage. Decoders are expensive, and shorts that extend beyond a half-second or so greatly increase the probability of a fried decoder.
In some instances, a person might not wish to have the DB150 cut power to the entire rail system. This may be the case when one has friends over who are sharing the train-running. If the rail power is cut, everybody has to mark time until the fault is found, corrected, and power restored. Also, some decoders have to go through the power-up sequence in the sounds. If you have an interim device that absorbs the shock of the short, the DB150 won't be so alarmed, and it won't protect itself and your layout decoders by tripping its circuit breakers. It will think it has a power-hog decoder such as a QSI starting up, and it will keep supplying power to the rails.
If a real hard short happens, the 12 volt tail light rated at about 2 amps will absorb the inrush of amperage and it will glow brightly, just like in a car. That service section will effectively die, the decoders are protected, and the DB150 merrily continues to supply full voltage and power to the rails. Your friends will know of the commotion, but they won't have to stop meeting their timetables. Meanwhile, you, seeing the glowing bulb, will know precisely where the short it, and that your decoder is thereby protected from that dangerous amperage.
I hope all this is clearer now: I suggest that you have lots of available amperage in the DB150, but maybe not. You should know how much you are likely to need as a maximum, probably add another 20%, and that should be your target. Will you need a full 5 amps of continuous service? If the DB150 is on the iffy side, then, yes, get a booster or two. But they're expensive, so please do a calculation. If your main goal is to break up the layout into safe electrical management areas, but your DB150 should have enough power for the whole layout, then use the bus and sub bus construction, wire much cheaper 1159 bulbs in series into one of the two wires comprising the sub, and after that take your feeders off the sub(s). You have stated the ovals will be electrically isolated, so each sub and bulb will manage the shorts when they occur on any one of those 'districts'. In DCC, we also speak of "power districts", but those would be with their own dedicated boosters and power....which I'm not convinced you need.
Yes thank you it makes almost perfect sense now that i know the details. It sounds like an excelent idea aswell. Now that you say i probably woln't need and additional booster, as i was only planning on running four to six locos at a time (two or three with sound) maximum. Hopefully this will be fine. Back to the sub power buss, the 2 amp lights would be wired directly in line with one, or both buss wires connecting the sub to the main?
Just making sure, because I had a major short a while back with my n scale layout (same booster, DB150) one of my steam locos, a Bachmann that i wired for dcc and sound had a meltdown on the track for no apparent reason. It made some noise, heated up and warped the plastic on the tender as it released all its smoke with no smoke unit. Yeah it sucked, oh well. I just hope the DB150 is not damaged, due to the fact it never shut down?? I'm guessing the decoder failed.
Yes, the decoder certainly failed, but I wouldn't blame it just yet. We don't really know the origin of the short, but we know it happened because the decoder took the worst of it. Hence the need for shorts protection in DCC, and tail light bulbs with a rating of about 2 amps or a bit more are super for absorbing all the dangerous power when the short happens. The preferred resistor is the lamp filament. Preferred by the electricity and preferred by you...and the decoder trembling nearby.
First, you mentioned in your first post that you intend to separate the three sections with gaps. With them separated, you were thinking about two boosters. I think I have convinced you that you probably don't need them. However, now that you have three isolated areas of your layout's track system, the DB150 can look after one of them, and the other two can be served by a single bulb....each.
Picture, a bus of two wires. Off it, in at least two places, will come two wires. Those are the subs. Place them where the feeders can be taken up to the rails in short runs to keep voltage losses to a minimum.
Soon after you run the two sub wires (and no reason not to continue to use the heavier bus wire), say within 6-12", and certainly before your first feeder wire, you will break one of those two wires, and solder a bulb into it...in series. You can get an automotive socket, or solder it as I did. You solder the end closest to the main bus to the base of the bulb, the nipple, and solder the other end to the side housing of the bulb. Good luck if it is chromed...it's a tough job getting solder to work, but I managed. Maybe wrapping the wire and trying only for friction contact is the better choice...you'll figure something out. Anyway, after that break and bulb placement, only then can you begin to run feeders up to the rails.
Now, if you have a short anywhere in any of those sections, the inrush of amperage will go preferentially through the bulb filament and light it up like a beacon. The DB150 won't mind because the amperage is being controlled, so it won't trip its protection circuits. Your other decoders won't shut down. You can go over to the troubled section, reach and fix the fault, at which the bulb will go out and your troubled engine should commence to operate. Works as niftily as that. And for about 1/10th of the cost.
Ok i see, the booster will control the outer oval with no light, the other two ovals will have thier own buss protected by the bulbs where they tie in to the main (booster) buss before the first feeder. Now lets say there is a short, when one of the two bulbs light will that oval shut down operation (power) for that oval only? I'm assuming yes, if i understand correctly. Sorry i'm being a pain. Thanks.
i believe all three districts need to be protected. If you don't protect the outer oval and you have a short on the outer loop the whole system will shut down, with no power to the any of the loops.
Got ya. Thank you.