DCC Explained

[melmerby]

I will open it up a little later and put some photos up as suggested ... until later

Good Idea

 

Keith

[Phil S]

Measuring 100m of wire in 1 piece with a multimeter is 100x more accurate than measuring 1 meter of wire or 1000x more accurate than measuring a typical length of wire used for a  short dropper connection.

( As a 10cm length of wire has very  low resistance - and is probably shorter than the meter leads.... and the meter leads may not be the original for which the meter circuitry was calibrated ... because the displayed value has to allow for the resistance of the leads etc.

 

For a wire intended for the 'bus' distribution - it may well be used in a length approaching 10m or even the 100m ... so again, measuring and being confident that it will not contribute to a voltage drop or failure-to-detect-a-short-circuit problem is a good idea not a joke.

 

I also suggested 100m reel measurement - because that could be done in a shop (eg late lamented MaplinsI) BEFORE choosing to buy.

[For those who remember their physics - and recall a Wheatstone bridge circuit - which would measure resistance accurately at Zero current - that could of course be used, but I don't think I've seen one for 30+years )

 

I will still avoid quoting/advocating specific wire sizes - just continuing to say that it is the users responsibility to ensure they are fit for purpose - whether as bus or dropper - it depends a lot on gauge - and likely number of locos , and sound and coach lighting in use.

(And to be aware that wires 'sold' for a 'specific use eg House Wiring - the current rating quoted is for that purpose and NOT your low-voltage railway purpose...  you need to ensure it is adequate for YOUR purpose - for both shorts AND lack-of Voltage Drop...)

 

For my most recent project, I have am using 'thinwall' automotive wiring - same copper content and structure as 'normal' but intended ONLY for voltages up to about 30V (ie 12 or 24V in vehicles) - this saves both the weight and environmental aspect of unwanted plastic coating thickness,(and theoretically allows a slightly higher current rating). Readily available in 100m reels or smaller (100m minimum for custom  colour striping).  [by contrast, PTFE coating allows a thinner wire to be used for the same current rating because it has a higher melting point - and can therefore run hotter safely - dissipating more heat .... but that extra resistance is not desirable in longer runs ! > Volt drop!]

 

And, as others have already corrected a/n/other poster:DCC  IS AC -   as recent discussion about unfitted locos placed on the track  reinforces - the ac waveform simply vibrates the motor, buzzing and heating it up whilst going nowhere.

 

The AVERAGE VOLTAGE of the DCC signal is 0,   its 0-peak value is usually in the range 12-22V  (16V for many european controllers by default - for any gauge eg Roco H0e, H0 ).    A Meter placed across the track will measure 0 on dc ranges, and  a voltage (which may not be accurate) on the AC range ( better meters give better results eg Fluke).   As with ALL ac waveforms, the peak-peak CAN be measured (easily on an oscilloscope 8-))   and the 0-PEAK voltage - which in the case of DCC is the same as the 'rms' voltage.

(For a sinusoidal ac waveform such as mains electricity,the  0-peak voltage is 1.4x the rms voltage normally displayed by a meter).

 

[ For the undesirable 'Loco 0 mode - the waveform is made assymetrical such that the AVERAGE is NO LONGER 0 - and as a result, the motor moves.  Larger motors may be able to absorb the unwanted heat - and LGB permit it - but may have extra components to filter ]

 

That a dcc waveform may be generated internally to the controller by dc pulses is not relevant  - because it is the 2-wire (2-rail/conductor) that forms the specified DCC waveform.  It might even be dc-coupled to the track - but that does not make it a 'dc'signal !!

 

My original point  for mentioning this (with an explanation that can be skipped by some readers- but is there for reference and understanding  ) was as a reminder to 'beginners' converting from analogue to DCC to ensure they REMOVED THE CAPACITORS present in their commercially-supplied track-power-connectors - (or risk damage to the controller ) 

 

Whilst I am glad that some posters report never having had problems - shorts from derailments or foreign objects on the track WILL occur - eg back in the days of Zero-1 I used to have a watch with a metal wrist strap  - it could get hot very quickly !!    I don't care whether you call it the 'coin test' (not a name originated by me. but I think US in origin)  - the principle is to short the track with something and ensure (not insure) that the controller cuts out   (or PSX/lower value breaker, if in an area beyond that - the idea being that the main controller then STAYS ON - allowing a separate (accessory) bus to change the offending point if that would cure the problem. eg from an overrun.

 

And finally, finally: Whilst a 'short' obviously drops the track voltage to ZERO  (loop is bus wire -> dropper -> track and back -> dropper -> bus wire); when using MULTIPLE locos in particular, but equally SOUND-fitted  or trains full of illuminated coaches  ( perhaps 20mA per 50mm of LEDstrip ) ....  'inadequate' wiring will result in a local drop in voltage  .... sound may cut out, decoders may 'restart' ...  Decoders should ALL 'work' above 7V on track ....   so the famous and undisputed V=IR  should help you ensure no more than (for example) a 2V drop.

 

It does not have to be a 'large' layout - an N gauge endless 'loop' layout I have seen had so much internal resistance that digital locos would 'drop out' ... the solution was, of course, to add   multiple power connections to the track .. of appropriate wire size(s).

[melmerby]

Some more OTT for beginners

Measuring 100m of wire in 1 piece with a multimeter is 100x more accurate than measuring 1 meter of wire or 1000x more accurate than measuring a typical length of wire used for a  short dropper connection.

( As a 10cm length of wire has very  low resistance - and is probably shorter than the meter leads.... and the meter leads may not be the original for which the meter circuitry was calibrated ... because the displayed value has to allow for the resistance of the leads etc.

 

As someone who was working in electronics for most of my life I always use 4 wire measurements for low resistance.

 

Keith

[WIMorrison]

I find that using the wire I have in my drawer works perfectly - and I haven’t the foggiest idea what gauge/resistance/impedance/capacity/etc it is - I do know though that it is either red, blue, orange or black, that it comes in 100m rolls and I have used 4 rolls them on this layout

[melmerby]

I find that using the wire I have in my drawer works perfectly - and I haven’t the foggiest idea what gauge/resistance/impedance/capacity/etc it is - I do know though that it is either red, blue, orange or black, that it comes in 100m rolls and I have used 4 rolls them on this layout

Short lengths will be nearly zero resistance so they will do the job. Simples.

 

Keith

[VicZA]

So ... as decided I was going to open up my new (old) loco and check if it has any support for DCC (pretty sure it does not) but alos how much space is available for these additions ... and came up against the following question: "how the %$$^$^&@ do you open up this loco":

 

I have had a look at the service sheet for it and pretty sure that the screws I need to get to to remove the body of the loco are the ones indicated as 200-014 (red square) on the diagram but how do I get to them? There are two pieces of body in the way of the screws, namely items 150-146 (blue square)

My questions thus:

( a ) How do I remove these two pieces to get to the screws as they seem very delicate?

( b ) Are these the correct screws to remove in order to lift off the cab?

( c ) Are there any other screws that I need to get to besides these?

( d ) do I have to disassemble the wheels too?

 

Please see attachments ....

 

 

Thanks

Vic

 

 

[Harlequin]

Hi Vic, (Nice graphics.)

 

( d ) No

( c ) No

( b ) Yes (the whole body, not just the cab)

( a ) Yes they are delicate and they might break at that tiny neck but they can be replaced easily. ("Bachmann NEM pockets" currently 10 for about £8 including couplings)

 

So, here's my suggestion: Insert a coupling (BL1998-1) into the pocket to reinforce the neck a bit. The two lugs on the coupling should emerge from the back of the pocket and sit either side of the neck.

Now find a tool with a thin flat blade and push it gently between the pocket and the chassis, twisting it gently one way and the other as you do.

The NEM pocket and coupling should start to ease out, allowing you to get the blade in deeper where you can twist it right underneath the delta shaped bit. Then it's safe to apply a bit more twisting force if needed without fear of breaking the neck.

The NEM pockets should pop out without too much problem.

 

When you remove the two screws that were obscured by the NEM pockets you should immediately feel that the body shell and chassis are loose but it may take some gentle wiggling and levering to actually separate them.

Edited September 19, 2018 by Harlequin

[VicZA]

Thanks HARLEQUIN ... that was easier than I thought and managed to remove everything without any damage. The photos below show the pieces apart and I think clearly show that there is no socket for DCC, so will have to do a modification - but it's a bit TIGHT in this chassis. As always, some questions:

( a ) anyone modified one of these that could share some tips?

( b ) does the DCC decoder fit above this PC board (assuming there is space)

( c ) or does the DCC decoder replace the PC Board that is currently in place?

 

Thanks

[VicZA]

@slngshotx:

 

Yep makes sense except for two things that I am still not clear about:

 

Remove the existing pcb, the orange & black are the supply to the decoder. Red & black to motor.

Remove and discard the PCB? Decoder completely replaces it?

Depending on the chip it may fit ok; however on mine I cut the metal lug off that the PCB screws too. The decoder then sits nice and flat on a bit of insulted double sided sticky or hot glue.
Which decoder did you use? Must it be a 6-pin, 8-pin, doesn't matter? what considerations do I need to take into account?

What are the changes of getting a SOUND decoder into this body?

[Harlequin]

Hi Vic,

 

Slngshotx's advice is not correct, I'm afraid.

 

Red and Black wires come up from the wheel pickups into the decoder.

Orange and Grey wires from the decoder should then be connected to the motor.

 

You need to buy a decoder that comes with flying wires, not a 6-pin or 8-pin plug/socket, and one that is small enough to site where your PCB currently is. So be careful of the width.

 

Edit: Sound makes things much more complicated. Some example installations are shown here: http://www.youchoos.co.uk/Index-Resource.php?L1=Guides&Item=BachmannPannier

Edited September 19, 2018 by Harlequin

[VicZA]

Phil ... I get it ... like this diagram shows:

 

Suppose (depending on the decoder) the additional wires are not used and hence not connected

... now to look for a decent decoder 

[GoingUnderground]

Folks .. again ... thanks for all the info so far - greatly appreciated.

 

A few more questions if I may ...

 

I have just received my latest loco which is a previously owned 8750 Tand (a beauty!) but I think it is only DC, so:

(a) how do you tell if it is DC, DCC or Analog bu looking at it "under the hood"?

(b) assuming it is DC - which I think it is - can I run it on a DCC track using a DCC controller (I have the Hornby R8213)?

© If I want to change it to DCC, what decoder do I need?

(d) Does anyone have a link to a you tube video (or similar) to show how this is done.

 

Thanks

I'm sorry, but I'm worried thst if you can't answer these questions yourself after doing all your reading, then I don't think you're quite ready to go DCC. Please don't think of this comment as a put-down or me being elitist, it's definitely not intended to be either. But your questions are basic ones which I'd have thought you would be able to answer for yourself. Because you're asking them, you may be at risk of damaging a decoder if you try to install one yourself if the loco isn't DCC Ready.

 

You can't rely on any markings on the loco as to whether it has a decoder fitted or not for the simple reason that it's secondhand and the previous owner(s) may have fitted a decoder to it if it didn't have one ex-works, or removed it if it did. Personally, I'd always remove the body first to see what's in there before putting it on any track.

 

If it's DCC Ready you'll see the socket and will know what interface you'll need a decoder to have, be it 6 pin, 8 pin, 21MTC, one of the PLuX variants, or Next18. If your model is the Bachmann DCC Ready one, then it should have the 8 pin socket, but a previous owner may hsve changed that or removed it altogether.

 

If it's already fitted with a dcoder you should be able to see it. You can tell the difference between a decoder and the blanking plug in a DCCReady loco as blanking plugs are usually very simple affairs with at most a few large components fitted to them, whereas a decoder will have many components, and possibly the makers name.

 

If it hasn't got a decoder.and you want to fit one then you'll need one, with the appropriate interface/plug, that can supply the maximum current that the motor needs, sometimes referred to as the stall current. The decoder specs will tell you the maximum current the decoder can supply. If it's not got a decoder and isn't DCC Ready then you'll either have to hard wire one which means getting a decoder with fly leads, or fitting an interface/socket yourself to convert it to DCC Ready and getting a decoder with that interface. If you fit your own interface make sure that there is space for it and the decoder.

 

If it hasn't got a decoder and is the Bachmann OO model with the split chassis, then fitting a decoder is possible, I've done it myself with a sound decoder, but it is much more work as you need to isolate the motor feeds from the chassis, and devising a way to attach the red and black wires on the decoder to the chassis, making electrical contact with each half. This means taking it apart and modifying the two halves of the chassis block. You'll also need to find space for the decoder, and if your decoder won't fit in the space occupied by the weight in the bunker, then it might mean removing the cab to remove the U shaped ballast weight in the panniers and smokebox. Also don't wrap the decoder in insulation to stop it touching the chassis block, put something on the block instead, like a thin piece of plasticard to stop the decoder touching it.

 

As others have already said, you can't run an analogue (loco without a decoder) on DCC unless your DCC controller has the "Loco 0" feature. However, Loco 0 is a throwback to the very early days of DCC, to entice folks to go DCC and using it isn't a good idea, as it can burn out the motor. That's why many DCC controllers, particularly the more modern Euopean ones, don't have it.

 

Please don't be discouraged by my comments. They are well-intentioned, as there's nothing more disheartening than starting something that is beyond you, or doing all the work but watch the decoder fry when you put the loco on the track because you've made a mistake, and I do speak from personal experience in both cases.

 

ADDED After seeing your post above. You can get a sound decoder in, but you'll need space for the speaker, I put mine in the bunker.

Edited September 19, 2018 by GoingUnderground

[melmerby]

Phil ... I get it ... like this diagram shows:

Decoder Connections 01.jpg

 

Suppose (depending on the decoder) the additional wires are not used and hence not connected

... now to look for a decent decoder 

A Lenz Standard + will fit* and is a good performer with this chassis but you will need to chop the 8 pin plug off. (and remove the onboard PCB)

Don't listen to anyone who reckons the super cheap decoders are good, they don't compare with brands like Lenz & Zimo which are only a few pounds more and definitely worth the extra.

 

Keith

The spare wires for lighting should be cut back

 

EDIT* "Should Fit" might be better phrasing than "will fit"

The wires to the motor can be straight from the decoder, removing the original ones from the PCB but you will need to join to the track feeds (red & black).

Edited September 19, 2018 by melmerby

[melmerby]

At least this topic has clarified the state of play with the Bachmann 57XX & 8750 Pannier chassis

My original assumption that all 32-200 onward had a socket was wrong.

The OPs loco is 32-200B and the last of the non DCC socket chassis.

 

31-900 series are definitely split chassis.

32-200, 32-200A & 32-200B are new all solid chassis NO DCC socket.

32-200DC is factory fitted DCC and presumably(?) has a socket.

All later ones are AFAIK socket fitted.

 

Keith

Edited September 19, 2018 by melmerby

[slngshotx]

Hi Vic,

 

Slngshotx's advice is not correct, I'm afraid.

 

Red and Black wires come up from the wheel pickups into the decoder.

Orange and Grey wires from the decoder should then be connected to the motor.

 

You need to buy a decoder that comes with flying wires, not a 6-pin or 8-pin plug/socket, and one that is small enough to site where your PCB currently is. So be careful of the width.

 

Edit: Sound makes things much more complicated. Some example installations are shown here: http://www.youchoos.co.uk/Index-Resource.php?L1=Guides&Item=BachmannPannier

 

Thanks yes sorry got it the wrong way around.

 

I would edit the post and correct but it seems to have disappeared.

[smokebox]

Thanks yes sorry got it the wrong way around.

 

I would edit the post and correct but it seems to have disappeared.

Just remember

 

Red & Black to the track (pickups)

Orange & Grey the other way (to the motor)

[Crewlisle]

To 'tigerburnie' in Comment 22 & anyone else who has been frightened away from DCC by some of these technical comments mirrored my concerns before going DCC in 2008.  Over the previous two or three years I had been reading very technical articles in various modelling magazines like in this current forum.  They kept referring to various electronic components, wire sizes/resistance & gave the impression you required an electronics degree to go DCC - until I thought about it from a common sense/practical angle.  It is no more difficult than wiring an ordinary DC layout.  If you read my attachment to Comment 24 'To DCC or not to DCC'  you will see my practical approach & why my layout has operated without problems for the last 10 years with a total of 52 locos, 32 Peco Code 100 Electrofrogs with power supplied only through the point blades (no polarity switches) & the only polarity switches on my layout are for the live diamond.

You can make DCC as simple or as complicated as you like.  My layout is wired for a basic DCC layout with only the actual track being DCC.  I have retained simple operation of points & signals - point operation using Peco studs on three miniature track diagrams & simple Peco solenoid motors ;four semaphores by simple mechanical operation (1.5mm welding wire & soldered cranks) & six 4 aspect Eckon colour light signals with cheap Maplin sliding switches on local control panels (one 'feather' & one light controlled by the position of the relevant points).  The main reasons for operating the points & signals like this is:

1.    Avoids additional wiring & accessory decoders.
2.    Saves a lot of money.
3.    It worked OK on my DC layout for over 25 years.  As the saying goes, 'If it ain't broke, don't fix it'!

 

Peter

Edited September 19, 2018 by Crewlisle

[Andymsa]

Peters points regarding the use of accessory decoders may be valid on a small layout. But a large layout is another matter, any form of automation needs accessory decoders. Then the size of the control panel or panels would be a factor. There be no flexibility in where you stand to operate your layout from, no such restrictions with accessory decoders. Then the amount of extra wiring for manual control that has to be run back to the control panel as opposed to an accessory decoder that is local to the points.

[VicZA]

Is a decoder that is classified as N scale only suitable for that scale or can it be used on a OO scale? I am thinking specifically of the Lenz Gold Mini decoder .... thinking that the smaller it is the easier it would be to fit in the loco chassis.

[tigerburnie]

To 'tigerburnie' in Comment 22 & anyone else who has been frightened away from DCC by some of these technical comments mirrored my concerns before going DCC in 2008.  Over the previous two or three years I had been reading very technical articles in various modelling magazines like in this current forum.  They kept referring to various electronic components, wire sizes/resistance & gave the impression you required an electronics degree to go DCC - until I thought about it from a common sense/practical angle.  It is no more difficult than wiring an ordinary DC layout.  If you read my attachment to Comment 24 'To DCC or not to DCC'  you will see my practical approach & why my layout has operated without problems for the last 10 years with a total of 52 locos, 32 Peco Code 100 Electrofrogs with power supplied only through the point blades (no polarity switches) & the only polarity switches on my layout are for the live diamond.

 

You can make DCC as simple or as complicated as you like.  My layout is wired for a basic DCC layout with only the actual track being DCC.  I have retained simple operation of points & signals - point operation using Peco studs on three miniature track diagrams & simple Peco solenoid motors ;four semaphores by simple mechanical operation (1.5mm welding wire & soldered cranks) & six 4 aspect Eckon colour light signals with cheap Maplin sliding switches on local control panels (one 'feather' & one light controlled by the position of the relevant points).  The main reasons for operating the points & signals like this is:

 

1.    Avoids additional wiring & accessory decoders.

2.    Saves a lot of money.

3.    It worked OK on my DC layout for over 25 years.  As the saying goes, 'If it ain't broke, don't fix it'!

 

Peter

 

Hi Peter, thanks for thinking of me, not scared by the thought of DCC, before retiring I used to write and modify PLC programs as part of my job as an engineer, also used to re-program Robots too in the automotive industry on their automated equipment. If I want sound I will run a soundtrack of some real live locos(at present I don't), if I really wanted several miles of wiring, I can do that too, I used to wire up control panels as part of my apprenticeship for marine radar equipment. What my railway model will do is run like the Great Central, which was mostly run mechanically, apart from some lighting and a few traffic light signals at Leicester station, it will take me back to my yoof when train spotting lineside.

[Nigelcliffe]

Is a decoder that is classified as N scale only suitable for that scale or can it be used on a OO scale? I am thinking specifically of the Lenz Gold Mini decoder .... thinking that the smaller it is the easier it would be to fit in the loco chassis.

 

The issue is current, not scale.    If the model has a low-ish current motor then a low current decoder will be OK.    In OO with recent models, its only some Heljan diesels which have high current motors where you might have problems, pretty much everything else won't be an issue with a smaller decoder.   That said, if there is room for a slightly larger decoder, then all things being equal, that decoder might be cheaper, have higher current handling (so less likely to be overloaded), won't tend to overheat as much (parts further apart), and so on. 

 

As for Lenz Gold Mini, its over-priced for the quality of control offered.  There are far better models at a fraction of the price, such as the Zimo 6-pin at £20, or even a fully wired Zimo at £30-something.   

The only reason to buy a Lenz Gold Mini would be to fit the Lenz Power-1 module to the decoder, but the Power-1 is huge, so you won't have the space for it if you were looking for a small decoder.....

[melmerby]

The Lenz Standard + V2 gives you 95% of a Gold at 50% of the price, along with the similarly priced Zimo MX series these are the only decoders I would use unless you want some extra functional ability that the cheaper (Approx £18) ones dont do

 

Keith

Edited September 20, 2018 by melmerby

[GoingUnderground]

Is a decoder that is classified as N scale only suitable for that scale or can it be used on a OO scale? I am thinking specifically of the Lenz Gold Mini decoder .... thinking that the smaller it is the easier it would be to fit in the loco chassis.

Techmically, a decoder classed as suitable for N may have a lower maximum voltage handling capability than one intended for OO or H0 or O gauge as the NMRA standard defines a lower maximum voltage for N decoders. Of course, individual manufacturers may design them for the same voltages as those for the larger scales.

 

But there is a reasonable margin between the output voltage of DCC controllers when set for OO or H0 and the maximum volage for N decoders.

 

The more important factor is the maximum current demand of the loco's motor and the maximum current output of the decoder. You can use N decoders in larger gauge models provided the decoder can deliver the current needed by the motor, and the DCC controller's output voltage is low enough.

 

I have an ESU LokSound 3.5 micro in my OO Bachmann split chassis 57xx pannier tank and it works fine with my ESU ECoS which is set to have an output voltage of 17 volts.

[Crewlisle]

Peters points regarding the use of accessory decoders may be valid on a small layout. But a large layout is another matter, any form of automation needs accessory decoders. Then the size of the control panel or panels would be a factor. There be no flexibility in where you stand to operate your layout from, no such restrictions with accessory decoders. Then the amount of extra wiring for manual control that has to be run back to the control panel as opposed to an accessory decoder that is local to the points.

 

Andy,

 

My mistake.  I forgot that the accessory decoders take their commands from the DCC signal.  The point I should have stressed is the requirement of another set of addresses to remember for the accessory/point motors. 

 

The wiring for the point solenoid motors was already in place & had worked without problems for over 25 years so why not continue using it instead of buying accessory switches?  The operation of the layout is no problem as it is all controlled from within the central operating well.  The exception at exhibitions is that one of my operators is seated on the outside of the layout at the bottom left hand side by the diesel shed & has a duplicate panel to control all the points for the sheds & goods yard.  He is also the main PR man for talking to visitors & allowing children to operate a loco with one finger hovering above the emergency stop button!  There should be more layouts at exhibitions which allow children to run a loco & encourage them into the hobby.

 

Peter

[Andymsa]

Hi Peter

 

I now see what you were getting at, if it is working and no issues why replace it. The idea allowing children is great but sadly many grow out of the train phase for more interesting things