bayesianbob Posted March 14, 2011 Share Posted March 14, 2011 Help needed by a novice. Please excuse my ignorance! A little background first. I've always wanted to have a layout ever since staying at my uncle's house as a kid. His was so large that when he moved, it was advertised as "large model railway with rolling stock - comes with 4 bedroom house and 2 acres!" Finally, I've taken the plunge... I have a large spare bedroom (approximately 5m x 4m). Ultimately, I'd like the layout to take over the entire room, but I'm not so daft as to think I could take on a project of that size as a novice. Initially, I've opted for an L, with the long tail 3m long and the short one 2m. Maximum depth will be about 1m. After a lot of humming and prevarication, I opted to model in N gauge with DCC control, which then pushed me towards continental, as they seem to be a bit better supplied with DCC kit than us Brits. I'm currently putting a design together on Anyrail. Once it's complete, I'll post it. Impatience got the better of me and I splurged on a Fleischmann DCC starter set. The Multimaus controller seems to be good enough to do everything I need in phase I and possibly beyond. One thing confuses me more than anything else. I'm pretty certain that I can manage the basic wiring, such as the primary bus for DCC, plus a secondary bus for accessory power and I'm a reasonably competent solderer. What scares me is the huge amount of chat in places such as this about turnouts in DCC-controlled layouts. From what I've been told, the Fleischmann turnouts need absolutely no modification at all. Given that DCC has been around for a while (decades) now, I find it odd that other (i.e. English) manufacturers haven't modified their turnouts so that you don't have to mess around with cutting wheels and Lord knows what else, just to make them work with DCC. Knowing that my current choice will end up costing somewhat more, I'll probably compromise and go for Peco track and turnouts in the fiddle yard. I think I should be OK with insulfrog turnouts there, so no modifications necessary. My ultimate question is: Am I doing the right thing, or have I been misinformed and will I end up tearing my expensive turnouts apart anyway? Answers in plain English only please!!! Link to comment Share on other sites More sharing options...
Edwin_m Posted March 14, 2011 Share Posted March 14, 2011 My experience with Peco N gauge turnouts is that you don't need to cut the rails but it is a good idea to connect a wire to the frog area and control its polarity by a switch attached to the motor. However this is only with Farish and Dapol stock - not sure whether there might be a problem with Fleischmann etc. There is also a risk of shorts on Insulfrogs, as the wheel may bridge between the two rails where they come (almost) together in the frog, and if you need to do extra wiring to get round this then you might as well have gone with Electrofrogs to start with. Unless someone else can comment on these types of stock you may have to buy a couple of Peco points and do some testing. Link to comment Share on other sites More sharing options...
F-UnitMad Posted March 14, 2011 Share Posted March 14, 2011 .... I find it odd that other (i.e. English) manufacturers haven't modified their turnouts so that you don't have to mess around ... just to make them work with DCC. ... I'm only just getting into all this DCC malarky myself... from what I understand of Peco points, the modifications talked about are simply to make them work better with DCC than they already do. I.E. they don't need modifying, but are electrically more reliable if they are... Link to comment Share on other sites More sharing options...
bayesianbob Posted March 14, 2011 Author Share Posted March 14, 2011 Thanks for this - it's a good start! Looks like it's easier than I thought, especially if I opt for motors with built-in polarity switches. Any experience with them? My experience with Peco N gauge turnouts is that you don't need to cut the rails but it is a good idea to connect a wire to the frog area and control its polarity by a switch attached to the motor. However this is only with Farish and Dapol stock - not sure whether there might be a problem with Fleischmann etc. There is also a risk of shorts on Insulfrogs, as the wheel may bridge between the two rails where they come (almost) together in the frog, and if you need to do extra wiring to get round this then you might as well have gone with Electrofrogs to start with. Unless someone else can comment on these types of stock you may have to buy a couple of Peco points and do some testing. Link to comment Share on other sites More sharing options...
Edwin_m Posted March 14, 2011 Share Posted March 14, 2011 I use Seep PM1s which are cheap but not the best bit of engineering. Peco do two types of add-on switch for their motors, which by repuation aren't great either. Most of the slow-motion designs include at least one polarity switch and are probably better if you have the cash and the space under the board. Whatever you do make sure the switch always goes over when the point is in mid-travel, otherwise you will get an intermittent short circuit. Link to comment Share on other sites More sharing options...
Etched Pixels Posted March 14, 2011 Share Posted March 14, 2011 There is definitely no need to saw up Peco points. The gaps in them are sufficiently huge that if you ever find an axle that shorts you need to fix the axle pronto as it'll be causing derailments and other problems. No problem with Kato ones and DCC either as they have internal frog switching. Fleischmann points come with little metal bits so you can set them not to switch power, but if you can afford Fleischmann track and points for a big layout perhaps you could just have the butler do it for you Feeding power via a switch to the frog is optional on the Peco ones. It's not a bad idea for high reliability as the blades are not perfectly reliable for contact so do need a good clean now and then otherwise. Hardly vital though. Link to comment Share on other sites More sharing options...
Kenton Posted March 15, 2011 Share Posted March 15, 2011 It often saddens me that the myth that DCC requires different track from DC still exists and gets propagated by some forums. There is no difference between good wiring in DC and DCC. Just that wiring for DC has evolved into taking shortcuts and bad practice over the years. If everyone wired the layout for DCC then added the required section breaks to make it operational for DC we would all be better off. But sadly, DC came first and the short-cuts seem to have become more the norm for wiring so we end up with layouts perceived as difficult to convert. I reality all that should be required is to throw section switches and run. Track works with both or neither. Link to comment Share on other sites More sharing options...
Adrian Wintle Posted March 15, 2011 Share Posted March 15, 2011 But sadly, DC came first and the short-cuts seem to have become more the norm for wiring so we end up with layouts perceived as difficult to convert. I reality all that should be required is to throw section switches and run. That is exactly what we do on our designed-for-DC exhibition layout (Peco Code 100). No problems at all. We can run DC operation or an alternative controller (DCC or Hornby Live Steam) with the flick of a switch. I've also had no issues with Kato Unitrack (both N and HO), Atlas and Peco N (Code 80), and Atlas N (Code 55). Adrian Link to comment Share on other sites More sharing options...
Edwin_m Posted March 15, 2011 Share Posted March 15, 2011 But sadly, DC came first and the short-cuts seem to have become more the norm for wiring so we end up with layouts perceived as difficult to convert. I reality all that should be required is to throw section switches and run. That should be so, but particularly for a large layout wired with thin wire there could be voltage drop problems which lead to the short circuit cutout being effective. I think I agree this is a consequence of not following good practice in DC wiring, but the greater maximum currents in DCC make the problem both more likely and more severe. The important point is that "throwing all the section switches" might not be enough. It is necesssary at least to coin test every section too. Link to comment Share on other sites More sharing options...
Kenton Posted March 15, 2011 Share Posted March 15, 2011 That should be so, but particularly for a large layout wired with thin wire there could be voltage drop problems which lead to the short circuit cutout being effective. I think I agree this is a consequence of not following good practice in DC wiring, but the greater maximum currents in DCC make the problem both more likely and more severe. The important point is that "throwing all the section switches" might not be enough. It is necessary at least to coin test every section too. I'm very much from the old school of thinking on layout wiring and eschew all of the shortcuts. I have always wired to a bus and always provide every length of track with its own droppers. I just think that the Peco light approach to minimal wiring is just wrong and would never wire up track that way. When wiring DCC I just don't see the requirement for a coin test (which I have grave doubts about its validity anyway) But a poorly wired DC layout with incomplete or leaky circuits is bound to present problems. I guess it is just the starting point you work from. Link to comment Share on other sites More sharing options...
Edwin_m Posted March 15, 2011 Share Posted March 15, 2011 I consider you need either to do a coin test or to measure directly the resistance of each feed, in order to be confident that a short circuit will cut out properly. Even if the cable and everything else is of suitable size, there is still the possibility of a bad joint or a poor connection that could increase resistance and then overheat in the event of a short circuit. Link to comment Share on other sites More sharing options...
Crosland Posted March 15, 2011 Share Posted March 15, 2011 When wiring DCC I just don't see the requirement for a coin test (which I have grace doubts about its validity anyway) What dooubts? Maybe we can dispel them. Andrew Crosland Link to comment Share on other sites More sharing options...
Crosland Posted March 15, 2011 Share Posted March 15, 2011 My experience with Peco N gauge turnouts is that you don't need to cut the rails but it is a good idea to connect a wire to the frog area and control its polarity by a switch attached to the motor. Leaving the built in switching through the point blades *and* switching the frog is a guaranteed way to get shorts if anything goes wrong with the points or the switch. Unless the point operation and the switch are perfectly synchronised (not always the case) you can end up with the point blades and switch trying to supply the frog from both rails at the same time. Andrew Crosland Link to comment Share on other sites More sharing options...
Edwin_m Posted March 15, 2011 Share Posted March 15, 2011 It works fine for me with both Seep motors and the Peco ones with switches attached. Maybe more of a problem where the motor drives through a flexible wire of some sort? Link to comment Share on other sites More sharing options...
Kenton Posted March 15, 2011 Share Posted March 15, 2011 a bad joint or a poor connection what's one of them then Link to comment Share on other sites More sharing options...
Pete the Elaner Posted March 15, 2011 Share Posted March 15, 2011 I consider you need either to do a coin test Please don't! The coin test is crude & inaccurate. I agree with Kenton about this. The aim is to do things correctly, right? So why use such a rough way to find faults? A positive result engages the system's safety cut-out. How can that be a good idea? Would you deliberately blow a household mains fuse to check that a device is working properly? I think not. The safety cut-out is well named. or to measure directly the resistance of each feed. That's much better. Disconnect your control system & replace it with a wire between the 2 supply contacts. Then switch your multimeter to measure resistance & check each section across its running rails. The lower resistance the better. & you can use exactly the same technique for a DC layout or anything else electrical for that matter. Surely that has to be better than asking your control system to throw its toys out of the pram! Link to comment Share on other sites More sharing options...
Etched Pixels Posted March 15, 2011 Share Posted March 15, 2011 Would you deliberately blow a household mains fuse to check that a device is working properly? Not a good analogy - testing a fuse is like testing matches before boxing them up. Earth leakage trips most definitely do get tested when doing the electrical tests for a building and getting certificates. The coin test is useful as a precautionary check because it's quick and it tells you if something is definitely wrong including your measuring and calculation. Link to comment Share on other sites More sharing options...
Etched Pixels Posted March 15, 2011 Share Posted March 15, 2011 Leaving the built in switching through the point blades *and* switching the frog is a guaranteed way to get shorts if anything goes wrong with the points or the switch. Unless the point operation and the switch are perfectly synchronised (not always the case) you can end up with the point blades and switch trying to supply the frog from both rails at the same time. The Peco N gauge points have quite large gaps between the wheels and the rails anyway and the switches on the motors have a fairly large "off" area. They were designed for the job so not surprisingly are actually arranged to do it.. You don't *need* to feed the frog anyway and some large and exhibition layouts run perfectly well without doing so. The real world says both that the Peco and SEEP motors with switches do the job without vandalising precision trackwork and that layouts without frogs fed work just fine but sometimes need a spot more care cleaning. Link to comment Share on other sites More sharing options...
Crosland Posted March 15, 2011 Share Posted March 15, 2011 Please don't! The coin test is crude & inaccurate. If you use a coin with a low enough resistance then it is an effective and accurate simulation of a short circuit. I agree with Kenton about this. The aim is to do things correctly, right? So why use such a rough way to find faults? A positive result engages the system's safety cut-out. How can that be a good idea? How else do you propose to test the safety cutout? Would you deliberately blow a household mains fuse to check that a device is working properly? I think not. The safety cut-out is well named. No, but you *should* regularly use the "test" button on an RCD, which is a much better comparison. Do you think that's also a bad idea? Disconnect your control system & replace it with a wire between the 2 supply contacts. Then switch your multimeter to measure resistance & check each section across its running rails. The lower resistance the better. All that shows is the resistance of the wiring. How do you know the boosters cutout is working? Andrew Crosland Link to comment Share on other sites More sharing options...
Edwin_m Posted March 15, 2011 Share Posted March 15, 2011 & you can use exactly the same technique for a DC layout or anything else electrical for that matter. You can't use it for a DCC layout employing diode block detectors, because the test voltage on the resistance meter is less than the voltage drop through the diodes. To get an accurate check of fault current in this situation you'd have to apply DC at DCC track voltage, via a large power supply, then measure the current quickly, before something melts! Link to comment Share on other sites More sharing options...
Pete the Elaner Posted March 22, 2011 Share Posted March 22, 2011 If you use a coin with a low enough resistance then it is an effective and accurate simulation of a short circuit. How do you know it will have low enough resistance? We're back to a meter again. A coin can never be accurate anyway. All it does it create a short & activate the cut-out. In what way is that accurate? If you don't know how to use a meter, please don't bark on about a coin being better because it is simply not true. Link to comment Share on other sites More sharing options...
Suzie Posted March 22, 2011 Share Posted March 22, 2011 How do you know it will have low enough resistance? We're back to a meter again. A coin can never be accurate anyway. All it does it create a short & activate the cut-out. In what way is that accurate? If you don't know how to use a meter, please don't bark on about a coin being better because it is simply not true. The type of meter used for low resistance testing of high current wiring is a big piece of kit that the average modeller does not posses. For a section powered by a 5A booster for example, the 'coin' only needs to have a resistance of less than two ohms - a chunk of copper currency should be well below that! The whole object of the exercise is to test two things:- 1. That the wiring is good enough to carry the 5A 2. That the booster shuts down when overloaded. If the wiring has been properly specified, the resistance will be as expected if the 'coin test' passes OK. Link to comment Share on other sites More sharing options...
RMweb Gold Donw Posted March 22, 2011 RMweb Gold Share Posted March 22, 2011 Wonderful things these forums. A novice asks a question and it degenerates to an argument over whether a coin test is a good idea. Aren't we confusing the poor fellow. Don Link to comment Share on other sites More sharing options...
Sunnysa Posted March 23, 2011 Share Posted March 23, 2011 The track used with DCC is really immaterial. All track will work if connected and wired correctly. Every piece of track, including points, should have power droppers from each rail to DCC system buss wires. The power droppers can be a smaller gauge than DCC buss wires. The so called coin test for DCC is a quick and easy way of finding out if the wiring has been done properly and is sufficiently big enough to carry the full current supplied by the DCC system. If the wiring is OK and done properly the system will shut down in Milli seconds. If not Ok the system may take much longer to shut down when a short occurs or not shut down at all. Do this at numerous places on the layout. Starting at further-est point from DCC system and work back towards System To test the overload in DCC system is working OK,before connecting to layout/track connect a pair of wires to track output,turn system on and short wires. If all OK system will shut down instantly. Some systems will boot up automatically when short is cleared. Some require a button push. BTW,although I am still learning I am not a DCC novice. Been using it nearly 16yrs. Cheers Ian Link to comment Share on other sites More sharing options...
Crosland Posted March 23, 2011 Share Posted March 23, 2011 How do you know it will have low enough resistance? We're back to a meter again. A coin can never be accurate anyway. All it does it create a short & activate the cut-out. In what way is that accurate? If it creates a short then that is an accurate representation of a short! It doesn't have to be a coin. The "coin test" or "dime tset" is just a euphemism for testing the response to a short circuit. If you don't know how to use a meter, please don't bark on about a coin being better because it is simply not true. I would never use a meter to create a short circuit :-) I think we may be talkling at cross purposes to some extent. Andrew Crosland Link to comment Share on other sites More sharing options...
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