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Prepared by G.Spencer-Salt 2009
Can you wire a light globe to a battery? If the answer is “yes,” read on, wiring a layout for command control is that simple, once you have two wires connected to a piece of track there are no operational restrictions on a locomotives on the track, a model railroad is a more complex than that and to achieve our dreams we have a few connections to hook up but unlike DC this is no need for complex panels and switch logic to achieve the operational outcome we are seeking. Start here. If you have a multi meter with a buzzer, use it as long as it is loud, if not, build a short detecting buzzer before you start any wiring, this is the first in piece of equipment you need do not wait until till the end and find out you have shorts, you are in for a lot of hard work. Attach the buzzer to the track while doing all wiring, any wiring error that you make that results in a short, will cause an immediate beep, if you have a team wiring several districts at once, temporarily jumper the main booster feeders together so only one beeper is needed, clip to the track with test clips ensuring the booster [s] are not connected at this time.
Buzzer
parts list and instructions. The battery pack listed takes 4 x AA battery's and is equipped with an on off switch, cut the 1 meter wire in half and solder one length to each of the test clips, connect one wire of the buzzer to one of the battery pack wires finally connect one of the lead to the remaining buzzer lead and the other to there remaining battery lead. Identify you track in some way. DCC track power is a amplified signal but looks like AC and electrically need the same gaps and wiring procedures that you used for a DC installation. You still have two wires and you need to know which is which, this is especially important topside with your track winding every which way, it's easy to loose track. Refer to the tracks as "Red", "Black", "A", "B", whatever you like but avoid "inside" and "outside" rail because unless you have a simple oval, chances are your inside rail will become your outside rail at some point. Used a colour code for all your wiring, this is of great importance when the wiring become more complex and you are integrating a large number of DCC components into the model railroads electrical system, develop a colour code and just stick to it! Layout noise. Electrical noise on any DCC equipped can come from any or all these sources principal sources listed: Track, Power and Bus. Cab Bus Noise on the cab bus is created simply by the action of multiple throttle just begin plugged and unplugged and there is little that we can do to alter this but the noise begin radiated from all other sources can swamp the weak signal on the command bus, this can be minimized by a few simple things. The flat multi core cables used to build a command bus between the command station and the plug points can be twisted to improve it ability to reject radiated noise, we recommend about 3 to 6 turns per meter, larger or club layouts consider the use of CAT 5 cable, it’s designed to prevent noise being radiated and or received, were long runs exist to plug points or other command bus related hardware like radio receivers on larger layouts this should be considered seriously. Installing the cab bus to the front and the power bus to the rear of the layout were possible this will help prevent the two interfering with each other, never bundle the power bus and command bus, even if it looks neat, as a rule of thumb try to keep them at least a 100 to 150 mm away from each other as a minimum if they have to pass over each other try to do it a 90 degrees. On larger layouts the use of a snubber on the Cab bus can help, there is no formal rule but were the cab bus exceeds 10 meters consider installing a snubber and again look at CAT 5 for the bus cables. A snubber circuit is shown below. Power Bus Noise on the power bus is generated by chatter that is the model railroad itself, it is created by motors, wheels, pickups, points operating and shorts. This noise will damage the signals [packets] but the systems are designed to cope with this, but at its worst will swamp the packets generated by the booster. Its presence is manifested by erratic operation of the DCC hardware, the possibility of this occurring is slight and unpredictable but when it doses it becomes the only explanation why one railroad is impossible to operate and a similar one is flawless. The worst of the example are low resistance shorts across points these are invisible because they do not exceed the capacity of the booster and thus never trigger an overload to alert the operator but results in short that is cutting in and out due to the operation of the track work and will create havoc. Track. Nickel silver rail, which is regarded as good conductor is nickel bearing brass and defiantly has no silver in it, rails only task in a well-wired layout using DCC is to locally deliver signal and power to you locomotive but should not be used as the primary means of delivery power around the model railroad. Good wiring will not fix bad track and there are many and articles and books on this subject, it you have not laid track before ask or read up there are a few tricks. Some people don't like to solder too many pieces of track together due to expansion considerations, you definitely need to consider the temperature swing in your layout room if your layout in a garage or shed that is unlined, thre is more about this in the wiring section. Alan Gartner's DCC site has a excellent explanation, so use the web at : http://www.wiringfordcc.com. If you do not want to wade thru all the data the best way to look at the issue is to realize copper has 1/100 [0.01] the loses that nickel silver rail dose for an equivalent cross section, use the copper wire of the power bus to deliver power around the layout and track to deliver power locally to each locomotive. Wiring. There is no fixed rules but we recommend the following general rules as follows. Classic 4 x 8 – 1.0 mm square bus with 0.4 mm square feeders or just with all 0.5 mm wire to a terminal strip Shed layout - 1.5 mm square bus with 0.4/0.5 mm square for feeders.Large layout – 1.5/2.0 mm square bus with 0.5 mm square feeders, were the terminal strips are installed to break up the power bus consider 2.0 mm sq from booster to master terminals, 1.5 / 1.0 mm between distribution terminals and 0.5 / 0.4 mm for feeders. Of course you can go lighter but consider telephone wire and hook up wire useless for model railroad use and if in doubt use heaver wire but remember that no layout has operated worse when by over sized wire the same cannot be same for the alternative. Many of the US publication talk in wire gauge the table below will help convert to the more common square millimetres used in Australia and New Zealand
Wiring. Rule 1 and the only rule All wiring must connect together mechanically, put simply this means solder, terminal strip, clips but in the end you must achieve an airtight point of mechanical connection. There are no short cuts and if take one you will regret it later, its that simple. Basic power bus The power bus is the cable that connects the model railroad to the command stations booster. A simple power bus will meet the needs of modellers building a classic 4 x 8 is two separate lengths of bare copper wire were they simply solder feeders to the track and then to the appropriate bus. Soldering is the quickest and cheapest options and can definitely be used for the classic 4 x 8 and small garage layouts use a buzzer, check that trains run after every work secessions. If you want to have signals, block occupancy detection you will have to be super careful and well organized and the use of terminal strip should be given consideration Divide and Conquer the Bus. For those you wish to take the simple’s route of a power bus and are considering a larger layout should consider dividing the layout into zones that can be switched on/off , this allows you to quickly isolate a section of layout that has an electrical problem. The bus can be cut and linked via switch located just under the fascia out of site, to run the layout just turn on all the switches to a trouble check, turn them all off and then turn them on one by one, its that simple. Running multiple bus to remote switches on a central panel will create what we were seeking to remove in the first place so remember what generally works best is the KISS principle. Wiring alert. Beware of connection of the bus circuits to any other voltage sources, if a DCC booster has either DC or AC power applied to its power bus booster failure is the most likely outcome and all the manufacturers can tell, it’s not covered by warranty, don't contact anything that is grounded to your home wiring if there is a short or a overload the DCC system may become a casualty. While on this issue but a little of the subject consider a cheap surge protector is the home dose not have one at the switchboard, there are a number of suicide models available that do a good job. I want all the bells and whistles. While a plain power bus is suitable for anyone wishing to run a layout under DCC once you decide you need block occupancy, signals, circuit breakers, PC interface then the use of terminal strips to develop a series of power bus’s is almost mandatory, because as modellers' we tend to develop the wiring as we go. Terminal strips allow quick debugging of problems because you are able to disconnect the feeders to isolate problems into smaller units, this also allows transfer of inputs from one zone to another to quickly to change logic, fix errors. The principle outline here is that the power bus which is supplied from a booster never is connected to the track it all ways is run thru a DCC circuit breaker. In practice this means that the circuit breakers protect each zone and the circuit breaker in the booster is now protect the wiring of the layout. A soldered circuit here will mean cutting your carefully soldered wires; soldered connections will work against your troubleshooting and logic development efforts, if you use terminals consider tinning [solder] all the wires together before inserting them into a screw terminal corrosion is you enemy over time, finally the terminal strips make diagnosis and corrections less difficult and should be considered for a larger layout. A problem with larger layouts in inductance developing in the power bus were long runs are required, there is no test for it existence and when it will occur. The general rule of thumb is were bus are getting over 30 feet the power bus wires should be twisted around one another in the order of 8- 10 turns a meter, this should be done for all the power bus in the system, feeders can be twisted but generally keeping then short and running at 90 degrees to the power bus as far as practical, avoid parallel runs and if they have to occur try to keep them 100 - 150 mm from the power bus. Feeders. Nickel silver rail is a poor conductor that is already established and speaking to modellers' who have successfully used DCC for 20+ years they have a simple rule to avoid all the confusion, just connect every piece of track mechanically to the power bus regardless of its length, its that simple. We recommend a maximum of two [2] full lengths of flex track or 2 meters [6 feet] to reduce the number of feeders but solder the two pieces together at the fishplates. Every piece of track must be wired to something and that can be another piece of track or the power bus but never count on a metal joiner to carry power to the next rail, its job is to keep track in align and will let you down, fact. Soldering ALL the joints may cause grief with thermal / humidity expansion and contraction problems if the layout is in a unlined shed, if you believe that your layout room is subject to large temperature fluctuations a better plan is to solder track together in 2 meters [2 ft] segments, attach a feeder wire to every piece of track. The goal is to not rely on a friction-slip-joint metal clip to carry any significant rail current and to not require rail current to flow more than 3 ft (1m) through the higher resistance of the rails, a 6ft soldered rail length limit is not critical. You may want to solder more rail joiners on curves to prevent kinking if there is provision for some rail/track movement, but here as well at track switches, so plan on dropping down multiple rail feeders to ensure good electrical continuity.Common return between boosters. When running a large layout all the power used by the boosters will have to be returned via a single wire. A couple of 5-amp booster can create 80 watts of power and with light wiring and or a dry joint there is a fire risk, in general were common returns are created keep them small and localized and they can aid in good wiring development especially when used in wiring zone, we would not recommend a layout wide common for the reason outline above but more importantly a wiring error could be spread layout wide and be very difficult to locate. How do I handle a reverse loop or wye? A simple reverse loop or wye can be operated with a DPDT switch just as you did for DC or automatically in DCC by installing an auto reverse module, this will allow locomotives to smoothly travel through the reverse loop without operator input and that why we went to DCC, right. The only problem with this arrangement is that only one locomotive can be cleared at a time, so if you wire this feature to more than one reverse loop and two locomotives or lighted carriage arrive at the same time a short will result and the system will shut down and to solve this each point will need a dedicated module. Insulate both rails between reverse sections and ensure that the joints are installed to the manufacturers recommendations ensure a feeder is within 300 mm [12 inches] as the short circuit trips the auto-reverse unit that are on offer. Insulate you point frogs as the manufacturers recommends, if in doubt ask. Remember that all locomotives in the reverse loop remain direction and speed independent and this allows you to use the reverse loop as a functioning parts of the model railroad - no lost real loss of real estate. Don’t power route any sidings Some of you want to power route stub sidings - don't! You need power to talk to a locomotive and if you do this you effectively isolate the locomotive from the command station, run two feeder wires to that stub siding just like you are going to do everywhere else - no exceptions. DCC Friendly Turnout or Points? We will not examine in any specific conversion but the concept in general. For those requiring more detail refer to Alan Gartners site http://www.wirringfordcc.com for specific manufacturer conversion details.
To convert any point the first task is to isolate the frog from the rest of the track. This is done simply by cutting thru the closure rail and by install in insulated rail joiners at the exit of the frog. I would recommend that the point of the cuts beat at least 20 mm [3/4”] back from the intersection point of the frog to provide a good gap between the A and B. Connect the remainder of the closure rail to it respective A or B rail placing these rails at the same potential and means that you can drag a screw driver thru a closed point with no short. Next we power route the appropriate A or B to the isolated frog as the task of as point is to change direction of the locomotive not act a electrical switch so the need to be employ a device designed to do the job, a switch the electrical kind. The switched power routing the frog can be implemented in any one of a number of ways. 1. Built into the switch machine like a Tortoise .. 2. Built into a ground throw like some made by Caboose Hobbies. 3. A micro switch 4. Contacts a manufacturer supplies for their switch machine like Peco, etc Warning: You will need two switches as these will changeover [one for each side] can occur before the point has made contact with the opposite rail - instant short. Power Route ONLY the Frog. DCC Friendly Rail Switch Solves the Problem of Shorting When Using Auxiliary Contacts! If you are using ground throws, you can use a switch built into some of them, or you can add a micro switch. Burying a micro switch is more work, but the switch will last practically forever. If the modellers counts on the manufacturer supplied point wipers (look at a Shinohara or Peco points) to power route the frog eventually these will fail as most of us want to ballast and paint the track work the loss to reduction in effectiveness of the wipers can be guaranteed by doing this and power routing via contacts or micro switch will be necessary. If adding micro switches a short may occur if the micro switch or contacts switch when one of the point rails is still contact with wrong rail. So the model is forced to disable the wipers on the rail switch to eliminate the potential of a short, with DCC friendly rail switches, the point and the stock rail are at the same potential so there is no potential of a short. Point wipers or not, there is simply nothing to worry about! Jumper the Point & Closure rail. The weakness of all manufactured points supplied is there dependence on the hinge or pressure between the blade and stock rail to power to the blade itself in HO these are as long as some power bogies and in N scale the locomotive itself. I have found that spot soldering a piece of 0.010" phosphor bronze wire [CMA] about 40 mm [1 3/4"] long at each end between both has enough flexure to not effect point operation but ensure reliable contact. This is best done at the time of installation and you can jumper using a small piece of 30 gauge wire across the hinge but these tend to break or inhibit the operation of the point rail. If you are using sound locomotives this is almost mandatory. Were do I put my Command Station? The basic rule is this. The closer two devices are to each other that talk to each other, the less chance of noise being a factor in the reliability of the communication. It like two people trying to talk to each other in a crowd of noise. The further apart you are form each other, the harder it is to hear each other. From a electrical point of view there are several advantages of putting the command station in the middle of the linear terminated bus for large layouts. 1) From a voltage drop standpoint, each leg handle less Cab supply current that simply means less voltage drops. 2) From a command station signal transmission standpoint, noise is reduced since noise on one leg will not crossover easily to the other leg. This essentially means the bus is split into two separate legs in this phase of communication. Since the command station is fixed in position relative to the bus. This benefit remains constant 3) From a command station signal reception standpoint, there is some improvement in that the distance between the active cab to the command station has been cut in half or less helping to reduce noise. But some noise from the remaining portion of the leg past the command station is still seen by the command station. The noise issue varies from cab jack to cab jack since there is always some variable distance from the active cab to the command station, it still much better than a command station being at the end of the line opposite of the cab! Snubbers for the Bus. All DCC bus's are generally unterminated, this means that they do not join up to make a circle and this will give good results for any small to medium size layout but as the layout size grows so dose the two bus's and this can result in unreliable operation. In general this is seen as erratic operation on various parts or the whole layout in the worst case, this results from noise created by reflected signals on the bus's, this results from a signal reaching the end of a unterminated bus and bouncing back, if problems occurs we need to install a snubber to give the signals reaching the end of a bus some were to go. In is generally accepted that after a bus reaches 10 meters snubbers should be considered, a snubber is simply a capacitor and resistor in series reducing the current drawn by the snubber. For the NCE systems the following values should give satisfactory results. Cab Bus - 0.01 mF 50V ceramic capacitor in series with a 100 - 150 ohm 1/2 watt resistor. Power Bus - 0.1 mF 50V ceramic capacitor in series with a 100 - 150 ohm 1.2 watt resistor Installing a programming track If you are installing a dedicated programming track and that is switched as per the NCE manual remember to run feeder from the programming track in a different colour code to the normal track code. If you feed the power from the track bus into the programming input on the command station you will damage the unit. Mixing DC and DCC If you cross a DCC into a DC power track, you will place the high powered "AC" DCC signal right into the input of your DC power pack, what happens next depends on the design of the DC power pack and DCC booster. "Boom" is a possible outcome. Remember that DC throttles were not designed with DCC being present at the same time, it is a big gamble that is simply not worth the risk.
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