Junctionmad

My own layout and my own view is that a separate layout bus is valuable but for fault finding and redundancy. Also track power faults don't then take out all the accessories as well. Also a layout bus is bidirectional whereas dcc is not

There is no particular point in running the accessories through DCC , unless you want to control them from a DCC throttle. If you want a more user friendly control panel , but want to reduce the wiring from it to the layout, then MERGs PTP-Lite or its full blown brother , CBUS , offers a very cost effective way to implement that. Yes , you have to solder the MERG kits up , but anyone that can build a panel could assemble the kits. Disclaimer : I am a MERG member

as you say the usual principle is to specify the output voltage at full load into a resistive load. Hence it's its theory the lowest voltage you'll see The load regulation percent will give an indication what the " no load " voltage will be. Cheap split bobbin could have load regulation approaching 20 %, meaning the no loss ( edit : load ) voltage could be 1/5 higher. Which is why you have to be careful over specifying transformers with too much load margin.

just taking your example , an assuming you are measuring the output with effectively very little load ( i.e. the meter ) , we can assume the ripple is zero for that low load ( i.e. I load tends to zero ) ( the Vripple at 1mA with that capacitor is approx 4mV) hence using my formula AC =( DC + 2.7 + Vripple ( pk)) /1.414 , gives ( 22.6 + 2.7 + 0 ) /1.414 = 25.3/1.414 = 17.89 ( well funny that ) I hope Nick G is now OK PS To answer the confusion generated at the top of this thread, the DC output of a smoothed bridge rectified AC is never higher then the peak AC but it will be higher then the VAC RMS ( unless the load is high and the ripple voltage is significant ) , This is because the average value of of the output , which is what is taken as DC is rated considerably by the capacitor, and of course the resulting input current profile is changed completely from a sine wave to a pulse of AC current as the diodes conduct once the capacitor discharges relative to the diode input voltage ( thats another story of course )

Just a point of definition here, DC is not the positive peak to peak of the rectified waveform. DC is the average of that waveform , the smoothing capacitor increases that average, as it releases " power " during the decreasing edge of the cycle, hence the DC Voltage rises when you add a suitable cap

That's quite all right

For plain AC to Dc full wave bridge rectification AC ( rms) = (DC + 2.7 + Vripple ) /1.414 I.e. For a DC voltage of 12 V , this results in a Vacrms of 11.5 rms or 16 V peak for a ripple voltage of 2v pk In order to generate a ripple voltage of that the formula c= I load /( F x Vripple ) where F is 100 Hz normally c = 1/100 * 2 , is 5000uf for a load of 1A Note there's more to this , includeding ripple current and load regulation calculations.

What problems are " people having with DCC " ?

Wow , I'm exactly and the same stage. I'm not going to stain thev plywood as I want to play down the difference between the points and the ready made track I'm thinking of spraying everything Halfords primer grey and then working beck to a consistent weathered sleeper look

7/0.2mm is "OK " for short distance 00 droppers , 16/0.2 is better wouldn't use bell wire even for bells, horrible stuff

I'm trialing Dinghams in 00. The two issues I've found are the loop pivot has a lot of slop and is tricky on bogie freight due to the swing of the buffer beam on corners I'm not yet convinced

depending on how you wire this up , if you have a common supply THEN you have a common ground, incorrect attention will cause any ground bounce due to the servo being potentially coupled into the digital control ground. equally inattention could cause ground loops, ideally in a common supply ( likely to be the most used approach ) , the servo ground and the micro ground should be a "star " configuration from a good low impedance ground point , preferably at or near the PSU. However in many layouts , there is a DC bus and servo loads can be very high especially if there simultaneously movement , and in many situations the micro and the servo driver are sitting connected somewhere along the DC bus. yes again what was the test , before adding the opto , a 33 foot extension to a standard servo cable ????? , sure I can make that twitch by sneezing at it Im not simply commenting to pass the time, but to point out that your design ( by chance or design ) actually does a significant number of things that eliminate servo twitch, but the opto part isnt actually the reason

agreed but any line driver would so this and in fact some thing like MAX 3461 RS422 driver would actually even be better , as its a true balanced line driver . when I made the comment , is was specially related to opto isolation, which is reality is bringing nothing to the party here Agreed re low impedance load, etc this is one of the main reasons we get servo twitch from interference, yes you are right that a low input impedance is best Also the 820 ohm pulp has a significant effect on reducing servo twitch by in essence lowering the inout impedance in , This is why MERG boards have a strong pullup when driving servos direct from a PIC IO pin There are three sources of twitch (A) Inadequate power supplies, causing brownout on the attached processor or the servo , coupled with power ground (B) air and power line interference from passing locos © Incorrect sequencing of I/O pins during startup and after pulse width pulse There are also issues around maintaining the last pulse width or suspending control signals In you example , the primary benefit is the low inout impedance circuit into the servo caused by the diode/resistor, this is the biggest part in achieving the test result you are seeing , wiithout a balanced line , the CMRR will be very low and induced currents will flow asymmetrically in the line just point this out, If you want a 30 foot line driver , then I suggest a balanced line driver is the way to go. Opto isolation is only really useful , if you have independent floating grounds ( or were deriving the servo power from DCC track signals or something ) given this is not a balanced line , its far from " inherently immune to interference "

I can't see how an isolator brings anything to the party. In fact depending on the sensitity of the opto if could increase the sensitivity of the circuit to interference. Also when the Op is off , depending on the output characteristics of the. Micro , this could actually leave the op floating or via a weak pull-up. On MERGs board a good strong pull up was needed. Note that as this is not a balanced line driver , interference is not injected equally and hence the CMRR is not great. Separating the servo supply from the micro is a recommended idea , but that doesn't need a opto. In the circuit above , it's likely that's there is a common supply somewhere so you need to be careful about ground loops and ground paths for the high current servo pulses The " test " that was performed isn't really any indication of the opto doing anything , what had you there before the opto was added.

Best of luck with your next endeavour. MDF Is just passable on vertical structures. But it's a pig of a material on horizontal surfaces , requiring multiple supports. In my opinion good quality European Birch ply is the best with MR grade ( moisture resistant ) being acceptable for indoors rather then the more expensive WBP grade

Beautiful layout If you ever find the time , a step by step guide to tree making would be a fantastic resource

You'll see in other posts , I foscued down on BPRC . My view is that Nmra need to make it a subset of DCC to ensure its future. Otherwise the likihood of chaos is high with competing systems and protocols. (,rather like the way auto DCC brake has gone ) It remains to be seen what develops. BPRC could just remain niche market. increasing the insides of models are ful, of " stuff" and it's hard to see it being widely suitable for OO/ HO etc I'm not against it. But it needs to complement DCC to become mainstream in my opinion.

actually that isn't true, merely because " it works " for you , does not make it better or for that fact worse. A field can be ploughed today by a man and a horse. For that "man" the solution " works ". However its clearly not better( in general ) . there is a debate that seeks to establish in general the best approach and thats valid , of course nothing condones a debate with any rancour

which is why emojis are provided , to convey situations that can be misleading in purely words

You are quilty of the very thing you complain about , that is interpretation of the results in a way that suggests the results are skewed. The fact is its a poll of 300 responses . firstly thats not bad as polls go, secondly you cannot make any assumptions over then those that have some basis of correlation So yes , your contention that DCC is broadly based across the hobby is valid, because their is a reasonable correlation against the age of participants However there is no correlation to support "guaranteed to produce the wrong answer……...we can conclude that DCC evangelists outnumber DC luddites by almost 2:1" If anything the survey works against DCC as many modellers have both DDC and DC , and in reality thats a DCC conversant modeller. Nor can we say they are DCC evangelists and DC luddities , since we have no survey data as to the technical competency of the respondents All we can say is that there is a 2:1 ratio in favour of DCC . after that we dont really know any thing else. but that ratio is there and verifiable by the poll.

my own viiew is that BPRCs future , i.e. a mainstream future, is it has to be inextrixably linked to DCC. NMRA needs to specify it as an addendum to the Dcc specs. This would allow a hybrid system , where DCC command stations could have adaptors to provide a DCC radio signal and decoders could have radio receivers etc , This would allow a mix and match and the use of existing DCC command and throttle units THis is only true in certain circumstances , often in any sort of DC layout other then a trivial situation , you have to either have selection or isolation switches and these have to be selected also . One only has to watch at any major exhibition, how section/isolation switches causes occasional confusion . Feeding power solely by point switches can result in completely dead sidings for example , where you cant shunt while keeping the main line running , The step up in wiring complexity arrives quite quickly in DC it should also be pointed out that BPRC removes that "select point " to select loco " advantage " as well of course But tio tackle a substantive part of the argument With the exception of a circle of set track and a single engine , DC in reality , has little to commend it . The main reason we still see DC layouts is a combination of lack of knowledge , a perception of complexity and the biggest of all, NIH ( not invented here ) i.e. inertia based on " what you know " IN the early days of DCC, yes expensive was a consideration, but these days , with mass produced decoders ( you know its mainstream when the Chinese are ripping off DCC decoders !!) and inexpensive command stations, the costs of DC taken as a whole including DC specific wiring costs , on anything other then a trivial layout is similar , and the absolute cost of DCC has fallen dramatically compared to the rest of railway modelling , where costs have increased . Decoders are now available from about £12 upwards and good quality Lenz or Zimo can be had at around £20-25. Command stations can be implemented for £50 upwards, and wen you remove the DC section switching ( typically run back to a control panel ) , inter base board connectors etc , costs begin to look similar Yes of course if you have a 100 loco collection then you are looking at 1200 quid to convert everything to DCC, arguably if you have a collection of that size, you have already invested 10s of thousands in the whole hobby over time. TO give you a sense of the simplicity, Our club tends to build " exhibition " layouts in 00. usually twin track roundy roundy, a simple station and a few sidings. The idea being that trains can be run frequently at exhibitions , but the lack of complexity means the operator can talk to the visitors recently we switched from point motors , fed back to control panels , to DCC operated points and signals , with NO control panel at all, everything is done from the DCC throttle. Now this isn't my idea of fun, but it reduces layout wiring, in both complexity and cost, cut down on inter baseboard connections, removed the need and space for a control panel ( which was replaced with an A4 page , giving the accessory numbers for the points and signals ) I accept , and fully understand that DC will always be with us, but I think , where I take issue is people trying to justify it , The real answer is DC will exist because it " appears " simple " to understand at a simplistic level and the NIH factor . discussions are fun !

No one " dismisses " DC , I recommend DCC because it's simpler overall , supports prototypical operation and can be integrated in things like automation and layout busses or extended to drive accessories. Overall baseboard wiring is simplified as a result Just like DC , DCC isn't going to be " superseded " , it will exist along side other methods for a long time. As for BPRC , unless we see a standards body get involved like NMRA , it's going nowhere , because it was the advent of standard setting, that spurred DCC. The other issue of BPRC , aside for the complexity of multi channel radio on a large layout , is that in any sort of large layout , there is considerable baseboard wiring for block sections detection etc, signals and points , in my experience , track wiring becomes the smallest part. The reality is that BPRC , is a solution looking for a problem , i.e. Layouts with poor running ( leaving aside garden railways ) , perhaps fixing the poor running might be done first. Unlike DCC over DC , BPRC doesn't really bring any additional to the party and by its very nature is always going to be more expensive then dcc. There is of course nothing to stop you fitting batteries to DCC locos either Furthermore we need standards for BPRC , we need two way radio , loco status reporting , etc. Then we still have In gauges under 0 gauge the challenge of where to fit the battery. If you look at modern centre drive diesels , fitted with a sound speaker , there isn't room now to fit anything , never mind a reasonable battery. This is then impossible in say small tank engines , where even fitting the DCC decoder is a challenge , This isn't going to change anytime soon. The other significant issue for BPRC is the inability to connect loco ID to a section of track , unlike DCC with railcom. Automation becomes even more difficult In a good layout , with good track , and decent locos, BPRC brings little operating advantage and that's its greatest challenge.

Given modern DCC decoders are the size of a 20p , I fail to understand the " lead weight" issue. Most DCC ready locos are the same weight irrespective As to the " hidden loco " issue. I don't believe that's a common problem. Very few fiddle yards have track overhead , dc or DCC as extracting derailed stock is a nightmare as is the whole purpose of a " fiddle " yard , to " fiddle" with stock. The important thing is to avoid " edge" cases , given enough peculiarities, anything can be justified. In. My case I have railcom , so I can determine the DCC address by looking at the control panel , DCC can do " everything " DC can do, the reverse isn't true. Also DCC would be better in your situation as the higher voltage on the track would be better , and the decoders can compensate for voltage fluctuation.

The exact same wiring will of course achieve the exact same thing in DCC also , if that is what you want

The main reason I tend to contribute to DCC versus DC is that its always DC " enthusiasts " that are negative about DC and rarely the other way around remember that many DCC modellers would have been former DC modellers , The reverse isnt usually true The usual issues are trotted out (a) costly , but with decoders at about £12 and throttles for less then a single loco , I would suggest this isn't true (b) Complexity , but the reality is that a multi controller DC layout with section switching , has more complexity and wiring then the equivalent DCC layout © reliability , digital electronics are very reliable and likely to be the last thing that fails on your layout typical of the mis-information would be this type of stuff one mistake !! , modern decoders are very robust and cheap , DCC command stations have extensive short circuit protection , its very hard to break a modern DCC system so , opposed to £££££££££, were are talking about £12-15 quid and you have to try very hard to blow it up . in DC the controller would have long ago failed and blown up IM all for a reasoned debate , but less of the shibboleths