What is the disadvantage of running a single large booster with enough reserve capability and separate breakers for each power district vs running a number of smaller boosters and the same number of breakers (one for each power district)? Example; 10 amp total requirement, 10 power districts with a CB for each district. One 20 amp booster (assuming there is such a thing) vs five, two amp boosters. 10 amps capacity either way, same number of districts, each with a breaker. Is there a issue for block occupancy detection?
It would depend on scale, though your comparison between a 20 and 5 amp booster would lead me to think you are using something between Z and HO. More amps means more power that's going to be turned into heat if a short occurs - even a 10 amp booster is overkill for N scale and could do some permanent damage to plastic trucks if a train derails.
It was only an example. Use any number you wish. I wanted to know if it matters either way regarding block occupancy detection, or any other 'feature' issue?
A single large booster, even if suitably protected ("centralized power"), would require longer bus runs just to get to the various power districts. With multiple lower powered boosters (i.e., "distributed power)", you are closer to the action and the amount of copper involved in distribution and the associated signal degradation is minimized. The accomodationd for occupancy detection (e.g., zone sub-busses) would be the same in either case.
there are not many 20amp dcc booster available as far as i know. they're all designed for largescale. therefore operating voltage is 18-24volts. way to much for any smaller scale. i'd go for a couple of smaller boosters.
Guys, again, the 20 amp was only an example for conveinance! Ok, how about the 'loss' from the throttle or command station (whatever you want to call it) to the booster? The length to the track attachment is the same either way (more or less). Right??
No, the length to the track is the primary difference between the two approaches. The basic lineup of DCC components is as follows: Throttle --> Command Station --> Booster(s) --> Track --> Locomotive(s) With centralized power, the distance from booster to track can be longer than distributed power, where the boosters are located near to the districts they power, and thus have lower distribution losses. The distance from throttle to command station (the "cab bus") is inmaterial, as it carries no power. The distance from the command station to the booster can range from 0.0" (i.e., it's in the same box), to hundreds of feet (convention sized layouts). In the distributed power case, you would have multiple boosters, each powering a section of track, and all slaved to the command station. With Digitrax, this is done via LocoNet RailSync, which also carries no power, that being added at the booster(s). Here's a good overview: http://www.mrdccu.com/graphics/pdf/WhatIsDCC.pdf
A booster " Boosts" a low current signal sent by the command system. That's how all boosters work no matter the manufacturer or even home built. As long as that low voltage signal reaches the booster, the output will be full power at the track connections. For a layout the size you describe, a single 5 amp command station/booster place approximately in the center would result in a bus run of about 30 feet. Use a decent sized bus wire to reduce voltage drop at the far end. A 5 amp booster should have more than enough power to handle N scale for a long time. If power becomes a problem add a second booster so that each one is powering 1/2 of the layout. Want to break the layout into power sub districts? Simply isolate sections and add a DCC circuit breakers for each section. I'm not going to recommend a bus wire size because doing so usually starts a flame war. Doug, you can take that one If you really want to get fancy or your detection system requires, that extra booster could be opto-isolated. Digitrax can furnish them on order. Lenz and CVP boosters have opto-coupled units. Others may have them as well. Martin Myers
My concern is data loss/corruption. As I understand it it shouldn't matter unless someone thinks different. The 'run length' between the command station and the track feeder is the same if I use one booster or five, correct? So, it then should not matter how many I use or don't use since the distance is the same for each district. If the 'booster' is positioned in the middle of the layout and feeds the circuit breakers for say, 10 districts, vs 10 boosters feeding 10 breakers, data wise no difference? Right? The only advantage of multiple boosters is redundancy, if one goes you have the others. With one, the whole layout goes down.
I think I understand the confusion. There are two types of data in play with DCC: the data from the throttle/cab to the command station, and the data which is encoded on the rails. The former is pure digital data, similar to the ethernet packets for your computer. They are extremely low power and very very fast pulses, able to travel over fairly long lengths with little loss. Typical cat5e cable is 24 or 26 AWG, and 500 foot lengths are common. This is the communication that is used to tell the command station (and any boosters) what to put out on the rails. The data on the rails is an approx 10KHz alternating current waveform, superimposed on a "full voltage" circuit. It is neither true DC or AC in its pure state, but is means to send information through an electric circuit. The waveforms and how to read them are the DCC standards and specifications, and not being an EE, I would hesitate to try to explain them further. This signal is very susceptible to distance loss and interference and is where the quasi-religious debates of wire gauge for buss and feeders start. Gartner's website does a great job of explaining. The distance that one worries about, although with 10x20 there is no real need to worry, is the distance from booster to farthest rail point -- never worry about data from throttle to command station, or command station to booster (at least not practically). Good rule of thumb is 40-50 feet, but that is easily extended/stretched and my even stating this could generate posts of "I have 60-80' with no issues". This all depends on buss wire size and rail composition (and even the solder joints), along with scale (all goes back to Ohm's Law: V=iR) and what constitutes R for the specific instance.
In theory possibly yes, in practice probably no. But also in practice you'd probably not notice a difference in operation. Well, no. If one goes you've lost a chunk of layout and unless you indulge in some sort of switchable cross-linking it will seriously impair operations until fixed. And having ten instead of one gives 10x the likelihood of one going pop. Sooo...?! Going back to your original question: There are two advantages to multiple boosters. One is that you can supply more power than may be available from any one single booster - but arguably moot unless you are building a massive layout. The only real advantage, and again you need a largish layout for it to hold, is that you can reduce the problems (mainly volt drop) of sending low voltage, high current power long distances. Each booster can be located near the middle of it's power district, but can have it's own mains-fed (110V in the US) power supply nearby, so the low volt runs are kept short. (If you just have one big PSU which sends 20V or so out to each booster you may as well have just one big booster as the losses will be similar.)
Sounds as a wise compromise is one for engines and the other for turnouts, lighting, signals etc. The books I have read state as short as every three feet for track feeders. That seems excessive. The other issue is maintaining circuit breaker protection and the famous "quarter" (or maybe nickel with N scale) test.
Don't confuse run length with feeder frequency. For DCC, you do need frequent feeders, and don't go any less the 6 feet (three feet is actually better). Run length is strict measurement from the booster to the farthest point, through buss wire, feed wire and rail.
What has not yet been really discussed is the power consumption calculation. This would include the locomotives, the sound decoders, the car lighting, but it would also cover any DCC devices used in the layout like occupancy detectors and stationary detectors or signals. These all consume power as well was the network access points, like the UP-5 or the UR-90/91/92 in the Digitrax world. It is only after all of these sources or power consumption are dealt with will you know how many boosters you will need to cover the need. For example, if you are going to use a BDL168, it needs 300ma of power to operate, plus it needs a track power connection and will consume another 60ma or so. Now the 300ma is not part of a booster load, but it is another power load on the layout. I used this to demonstrate the idea of the consumption of power and not as a reason for power districts using multiple boosters. In fact, it has been recommended by several folks, if you have a substantial amount of stationary decoders, signal boards etc, then you may want to have a dedicated booster to power all of the devices and not use the track power. This keeps the track power steady even if you are throwing several turnouts. If the turnout motors are getting their power from the track, depending on the number of switch machines and the type of switch machine, it may draw a substantial amount of power off the tracks and that would affect the locomotive performance. The key word is substantial. There are many factors that can affect this. It all boils down to how stable you want you operations to be. Another example, I have an Ntrak module set that is 32 feet long. It is a switching/mainline combines set that has a total of 12 DS64's controlling 62 turnouts. One route would affect up to 12 turnouts, that being that a few of the stationary addresses are crossovers. If this was track powered, that would be the load of 10 Peco switch machines and that would use a pretty good power spike. Most cases things are not this bad, but even in a small yard, the power demand spike can be substantial. In this case, I do have a dedicated booster for all of the DS64's and the BDL168's and the Team Digital SIC24AD's. In this manner, with allof the signals and switches running, track power is never affected. This set is also it's own power district, and has been as far as 150 feet away from the main controller and had no issues with packet loss or corruption. In the final analysis, the DCC footprint is different for every layout based on the needs of the layout and the way the owner plans to operate. There are ways to save money using just a controller, but that increases costs elsewhere in the form of the wire needed to minimized resistance losses in the track and the wire. Any area of the layout that is prone to derailments, like in a switching yard, may want to be on a separate booster so that the layout does not go down if there is a derail in the yard. The same would go in a staging area. SO it is more about what you want to be stable in running your layout than anything else. This will help you decide the number of boosters etc to plan for.
I haven't even decided even if I will switch to DCC, let alone which system I would go with. I looked over Digitrax, but probably ruled them out due to those controllers with all the buttons which I don't like at all and no conventional throttle except in their basic system. I'm just in the process of building the room the layout will hopefully go in.
The Digitrax model was only used as an example on where power gets used that you may not think about. Similar products do the same things for all of the vendors. It was only to show a thought process when implementing DCC. There are many things to consider. Personally I no longer use Digitrax either, but for completely different reasons. Perhaps you should focus more now on the layout and then come back to this once you are ready to seriously consider DCC. Maybe a lot of the answers will make a lot more sense then. I am not trying to push you away, it is just that you do not seem to have made up your mind yet. There are ways you can build DC now for effortless DCC conversion later, but you have not ever gone in that direction. It does not have to be an All-In situation. We all want to help you out, but you have to know what you want to do before any of this is meaningful. Better answers to your questions would be available if you posted a track plan or some photos of the trackwork in question. Then the answers could be dialed in instead of the hand waving going on now.
From another thread, attached are jpg's of the proposed layout. There are 'issues' as it stands now (namely excessive curves & the universal x-overs are drawn way too short, which I now have corrected). I will widen each 'end' to 3 1/2 ' to increase the radius of those curves since they are the sharpest on the layout. I have no 86' racks or TTX cars, the longest are 70' (or so) passenger. Regarding wiring for DC and later graduation into DCC, that is additional work for a control panel with all the SPDT toggles etc. I would be doing double duty, only to remove them and build another panel w/o all those extra 'holes'
I'm not sure what you mean by a "conventional" throttle, or what you consider a "basic" system, but the NCE Power Cab has 34 buttons and 1 knob compared to the Digitrax DT402 with 32 buttons and 2 knobs and Zephyr Xtra with 24 buttons and 1 knob. The utility throttles have a similar comparison (17 buttons, 1 knob for the Cab 04 and 8 buttons and 1 knob for the UT4). I think if you compare the actual features and capabilities you will find pluses and minuses for both systems. ...and don't get hung up on buttons. You don't use them all anyway, and a couple of extras are always handy <G>.
It all depends on what you are going to operate on your layout also.I am using Ho and 3 digitrax 5 amp boosters [1 dcs 100 and 2 db 150s]the reason, My main lines are about 350 ft each and I run double headers one with sound and if i need a pusher or 2 to help and a couple switchers doing local work, that will use up about half of the 5 amps.The mains are double gaped in case I want to crossover to another district or siding. My yard uses 400 feet of track, so I use a separate booster for it, I don't run any switch machines or any other extras from the track power. All my track joiners are soldered except for expansion gaps and power feeds every 6 feet.The boosters are dead center for each main for equal power distribution. This is my choice and it works very well for me, some say over kill but that's the way I wanted it,It's been working for almost 4 years with out any problems and if there was a short it would take just a few minutes to find it.It will depend the size of your layout and what you want to plan operate and what and how many you operate and the size of your power wire.It's yours to build and operate just have fun and experiment it won't take long to figure it out ,Jim.
