How Many Bus Terminators is OK

[PJR_slo]

It's going to be quite an enormous layout before it is wavelengths long at 8kHz (I'll let you do the maths on a Sunday morning thanks - we are talking speed of light divided by 2 x pi x frequency).

Hi Fishman

 

Read your post this morning; been out all day, but this formula of yours has been going round in my head...  Where does the 2 x Pi come from?

 

From my calculations when I was out, the wavelength came to more than 37 KM.  Have just confirmed that using an online calculator.  That is simply speed of light divided by frequency.

 

Please expand my knowledge.

 

Thanks 

 

Peter

[Greynut]

I'm finding the theory interesting in the way it relates to the practical aspect of DCC and layout design. I didn't have a clue that so many things might be (are) involved - and I bet that I'm not alone.

 

As for my 10 pointed star, it seemed the best way to go. Initially, I looked at the bus runs as 4, perhaps 5,  'T' shaped busses - but as they will all connect at the same eLink power output - yep ... it's more like a star.

 

I arrived at the 'T' idea because of previously reading about what seems to becoming the 10 metre rule. If I fed the busses at their end, by the time they had circled the room, I would have ended up with 4 or 5 busses around 35'. I also veered off the idea of using the busses in a ring shape. So, with straight bus runs - according to the 10m rule - I would have had ends that would have needed suppressing.

 

By feeding power in with the busses running off in a 'T' shape - right and left from the power source - that gives a max of 17 -18' per individual bus length. I still was not certain whether I needed suppressors, as the overall bus lengths were still the same 35 odd feet. Even though the feed was central, I wondered if a spike ring could still resonate and build through the full length of the bus in a short. If it could - how many terminating suppressors would I need.

 

It would seem that I did the right thing and that the shortened right and left busses are not as subject to a spike doing damage. So in asking the question, I have been able to think things through in a step-by-step way as info was added - cheers everyone!!

[Chrissaf]

Ray,

Glad you're happy with the outcome of this 'long and winding road' thread. It's definitely had its ups and downs over this last week. I think we have all learnt new things. I daresay in time we all will be collaborating again around some suitably challenging topic.

And hasn't Peter's layout thread in 'General Discussion' been a big success too.

Best Wishes.

Chris

[Fishmanoz]

Peter, you are perfectly correct, forget the 2pi.  I told you it was Sunday morning.  It's 2pi x omega, not F.

 

Greynut, again I refer you to Mark Gurries. Buses can be considered independent, including the branches of you Ts, and their length is the total from the controller to the bus end of each branch.  And at the power level and that length, he says they may need to be suppressed, not that they will definitely need suppression.  So you could try sucking it to see. 

[PJR_slo]

So you could try sucking it to see. 

 

Fishman - That would be my suggestion.  It would be simple to add later if issues arise.  And thank you for the clarification - I am no longer as confused as I was!

 

Peter

[RDS]

It's no wonder people think that DCC is complicated and if I was a new member thinking about a DCC layout reading this, I would be put off too!!!

Note to potential DCC users:  You don't need any of this.

[Greynut]

Fishmanoz - I'm going to do just that. As every layout is different, how things affect it is going to be different as well - but it's handy to be aware of possible problems and how to counter them IF they show up.

 

RDS, although I started this thread, I do agree with you. I want to simply enjoy my setup and I think that this discussion has helped me to do this. Not in the technicality of it all. Although I found that interesting, it's up to a reader if they want to go through that - but if that reader was having problems, then surely they would like to know that it's covered somewhere on here. In my particular case finding out that things could happen but also getting the reassurance that they probably won't helps me relax ... get on ... and enjoy.

[RDS]

Hi Greynut

Yes, I understand and I agree it is up to members to decide but there are many people who think that DCC is complicated and it really isn't.

Actually, I also started a thread (a little futher down than yours) titled ' Do Sidings need Electronic Termination' because I have a layout with 17 sidings that is powered by just 1 connection to the entire layout and I was wondering if I should have some terminations (or suppressors as I think is their correct term).

[PJ_model_trains]

Hi Greynut

Yes, I understand and I agree it is up to members to decide but there are many people who think that DCC is complicated and it really isn't.

Actually, I also started a thread (a little futher down than yours) titled ' Do Sidings need Electronic Termination' because I have a layout with 17 sidings that is powered by just 1 connection to the entire layout and I was wondering if I should have some terminations (or suppressors as I think is their correct term).

 

Hi RDS

You are so right, DCC is not hard, it is just different. And like anything different, there are new things to learn.

DCC is definately the way forward. 

PJ

[Greynut]

Hi RDS and PJ.

RDS, I was reading your 'Do Sidings need Electronic Termination' thread as it was added to. It certainly has a bearing on this one and made interesting reading. I didn't add any advice as I'm learning all this myself ... as you've probably noticed.

 

I don't think entry to DCC itself is complicated - it's when you start to push the boundaries a bit (or you think you might be pushing them). Anyone coming in new to DCC and starting with a small layout doesn't need to worry too much about the techie side. But when people try to transfer existing DC layouts to DCC, or a DCC layout starts to get problems that can't be accounted for - then maybe this kind of thread and your Sidings thread could prove helpful. I see that you came to the same conclusion as me - use a single terminating suppressor ... more to err on the safety side than whether it's strictly needed.

 

In a few years, this might be a standard thing to do and manufacturers might include advice saying 'If your layout gets to this point - then ...' I think it's forums and threads like ours that move things onwards in that direction, as well as helping us when we needed it.

[RDS]

 ... Hi RDS ...

 

Hi PJ, Good to hear from you, I have been missing my regular dose of LD and Signalling.

[PJ_model_trains]

Hi RDS

 

The rumble of power feeds/droppers continues.  I think with one power feed you are extremely lucky not to have problems. I say that not of my own experience, although as you know I have installed droppers on every other section of rail, I say it because of the reasons given by specialists.

 

I know what some will say, I only have one power feed and it works alright!  Some say they can skate on ice and it is safe, then something goes wrong. There are good reasons to have the droppers installed, and if you have the droppers you also first install a DCC Bus. Having installed a DCC Bus you add the ceramic capacitor and resistors to each leg of the bus, spur/star or radial methods.  The question I think you are referring to is should you include them at the end of your sidings as these become in effect spurs. I cannot advise you on that but they are recommended on the spurs of the DCC Bus which in effect would respond to a problem before the track, at the end of a siding the problem would surely occur on the track before the capacitor/restistor.

 

http://www.brian-lambert.co.uk/DCC.html#On  

 

PJ

[PJ_model_trains]

 ... Hi RDS ...

 

Hi PJ, Good to hear from you, I have been missing my regular dose of LD and Signalling.

 

Hi RDS

 

Sorry you missed me   ;o)

 

To be honest I had had enough of the signal issue and decided to take a break, five months on and signals still don't work as they should. It concerns me regarding Loco Detection.  I am sure LD will be good for controlling speed but as for using it with signals I have my concerns. (Hopefully HRMS will fix the issues which should, hopefully reassure me, we will have to see)

 

I decided to have a break and do something else, although we do have our discussions, I have improved the wiring to my layout by adding a neon lit fused spur and backing box, all power goes via this switch to a slim gang of 4 sockets that feed the eLink, the lighting, one for LD when it comes and a spare for soldering or anything else. Much neater, much safer and I don't forget to switch everything on the layout off when I finish.

 

PJ

[Fishmanoz]

Hi PJ, just on sidings, you may note there is a reference in here to Mark Gurries and that he has a rule of thumb on possibly needing suppressors on lower power buses (< 5 Amps) over 10m long.  So you can pretty much forget sidings as such, just look at the branches of your bus.

[PJ_model_trains]

Hi PJ, just on sidings, you may note there is a reference in here to Mark Gurries and that he has a rule of thumb on possibly needing suppressors on lower power buses (< 5 Amps) over 10m long.  So you can pretty much forget sidings as such, just look at the branches of your bus.

 

I totally agree they are required to the branches of the DCC Bus; spiral, radial, this is as recommended also by Brian Lambert. (As is the importrance of having a DCC Bus).

 

That was not the issue being discussed, as I read it, RDS was asking the question on the previous page, regarding his sidings, he doesn't have a DCC Bus, he only has one power supply to his layout and has 17 sidings.

 

PJ

[Yelrow]

I agree with RDS,  hornby have no bus on their in house layout, nor i  lot of wasted time, wire and solder. Nothing on train set boxes about buses. Still 3 usually come at once. Not here of course, non existent. quite right too (tongue in cheek), john

[PJ_model_trains]

Hello again John

 

To have a DCC Bus or not to have one is up to each person to decide. There are a few people on here running with one power connection and at present it is working for them but, we should not ignore what the specialists say and why they say we should have one.

 

If your Doctor gives you some advice so that you live longer do you ignore him?  If an Health and Safety officer says you must do this it is safer do you ignore him? If an electrical engineer, qualified in his line of work says you should do this or that and gives a reason for saying it do we just ignore him?  It is no different then to a person saying do not skate on the ice you may fall in and drown, there are a few skating on the ice it must be safe. There are reasons for saying it, there are risks for not doing what the specialist says, it is out choice.

 

I am not saying you must install a DCC Bus, just referring to statements made by specialists, the rest is down to the individual. Risk accessment John.  My decision to install one was based on what the specialists say, it was also based on the fact it is easier to do when starting out than to do later when a layout is established.

 

PJ

[PJ_model_trains]

I agree with RDS,  hornby have no bus on their in house layout, nor i  lot of wasted time, wire and solder. Nothing on train set boxes about buses. Still 3 usually come at once. Not here of course, non existent. quite right too (tongue in cheek), john

 

Hello John

 

You are so right, it doesn't say anything about Buses on the train box... that is because it is a train bos  LOL.

 

It is a common fact that bubses always seem to come together. Do you know why 3 buses come at once?

 

PJ

[Yelrow]

Pj i am horrified that you dont regard hornby as experts. The experts ( manufacturers) dont use or recommend a bus.. I dont think a bus comes under Health and safety. Joking apart, nice to see you are still in good form, after your signal strife. Thank god you have not had to worry about Loco recognition, as well. Will that require a health and safety, or doctors certificate. On another matter, how is your TTS yellow submarine/ diesel. Is it a good buy. john

[PJ_model_trains]

Pj i am horrified that you dont regard hornby as experts. The experts ( manufacturers) dont use or recommend a bus.. I dont think a bus comes under Health and safety. Joking apart, nice to see you are still in good form, after your signal strife. Thank god you have not had to worry about Loco recognition, as well. Will that require a health and safety, or doctors certificate. On another matter, how is your TTS yellow submarine/ diesel. Is it a good buy. john

 

Hello John

 

I am not sure on the statement  'Hornby do not recommend a DCC Bus', I think they would be silly to makesuch a statement, to be honest I think it doubtful they have actually said that. I will however hold my hand up if proved to be wrong.  

 

They may however have said, 'we only have one power connector to our layout' that is totally different to saying they do not recommend a DCC Bus.  I can understand Hornby only having one power supply as it is important for them to test their products they are selling.

 

I am not worried about Loco Detection John, I am also not worried about Loco Recognition. I can recognise my trains and just can't detect them   ;o)

 

Thanks for asking about my TTS yellow submarine? But, I chose not to purchase one. To me it is brighter than a banana and sounds like a tractor, as all Class 37's do.  Although part of the railway network, to me this train is to loud!  No not the sound John, the colour.  If ever a train 'needs weathering' the Class 37 Network Rail model certainly does, it needs more than a little muck though!  

 

TTS Yellow submarine... I like that  ;o)  But not near my fishing lake!  LOL

 

PJ

[Graskie]

Beware so-called specialists, PJ. I believe I have put this on a previous thread some time ago. About 6-7 years ago one of my GPs told me not to go into hospital, in case I caught something. I was desperately ill with severe congestive heart failure whereas, contrary to my medical history, he had apparently diagnosed pancreatic cancer. I only just survived when I eventually went into hospital and they didn't think I'd last the night. I have also had some other bad advice from GPs. That's just one area of speciality and I'm sure people have to be just a bit clued up themselves in order to even discuss things with any expert.

 

I have had no problems over 20 years on my layout due to not having a bus, DC and DCC. I well recogise, however, that when I switch to RM operation of all my pointwork, it might not be a bad idea to set up a combined track and  accessory feed bus first.

[PJ_model_trains]

Good morning Graskie

 

The items mentioned were examples, some say you don't need a DCC Bus I haven't got one and it works OK. It may now... how long have you had DCC, how many points, how many signals, how many trains have sound and how many run at once. The question is... how much a person is going to add to their layout? The more a person adds the bigger the risk of problems. 

 

Then there is wear and tear of your layout, frequent changing of points, expansion and contraction, efficiency of fish plates, etc, etc. What works for a period may give problems as time goes on.  There are also the things we cannot actually see which reduce efficiency and in turn effect how far a train goes in a set time (using programs) speed or stopping of a loco.

 

It is nice that you say 'it might not be a bad idea' but, that is your choice Graskie, it is down to everyone to decide for themselves if and when they install a DCC Bus.  For me, all the reasons the specialists say to fit a DCC Bus makes good sense, excellent sense I feel, I also feel it is easier to fit one at the beginning than it is to do it to do it later. But they are my considerations based on sensible recommendations by the specialists, in this case qualified electric people not doctors. I am with you all the way with doctors, although most are good, our bodies are more complicated than signalling and loco detection. I was prescribed 13 different lots of drugs by 3 doctors, one prescribed 10 of them. The result I ended up in an isolation ward, called the yellow man, I almost died of liver failure which has caused me a lot of problems since, I annot have aneasthetic and have to be careful what drugs I take, not easy as we get older!

 

Keeping to the topic at hand, to install a DCC Bus or not to install a DCC Bus, that is the question. Is it right to say, I don't have a DCC Bus and mine works alright, is it right to say you should have a DCC Bus the answer to both is No. What is important however, I think, is to tell people the facts and what the specialists recommend and let the person reading decide if they want to or think they should install a DCC Bus. The way I look at it is, it is not two people talking in a forum, it is many reading it. Therefore by what is written is influencing those seeking to decide what to do. I would hate to say I don't have a DCC Bus and don't have any issues, influencing the new person to the hobby one is not needed and further down the line they wish they had done so. We must give the facts and the recommendations and let the person decide for themselves.  I have never said, you must have a DCC Bus but I always (as you have noticed LOL) say... the specialists say this or recommend that.

 

PJ