DCC for dummies

[Junctionmad]

3 hours ago, Pete the Elaner said:

MERG now produce a 12v DC version. This seems to be more readily available than the 16v AC one.

 Most MERG modules have moved away from AC power 

[ianh]

The MERG DCC accessory decoders still use 16v AC. The solenoid decoder/driver uses the rectified AC to drive the on board CDU.

 

The newer MERG CBUS modules use 12V DC and the older modules can be converted to DC.   The 12V CBUS solenoid driver module uses a voltage doubler to provide about 22V for the on board CDU.

 

Ian H

 

[tigerburnie]

So let's pretend I have decided on my controller and the track is wired up, bearing in mind my prime reason for contemplating the leap to DCC, just how many pins does a decoder need, I hadn't realized it could vary from half a dozen to near two dozen, is there a benefit if it has more pins, or is this down to which chip manufacturer you choose?

[WIMorrison]

More pins equals more functions

[Phil S]

To expand upon WIM's answer .....

For hardware functions, then each output requires a connection to the outside world (loco) from the decoder .

so 2 wires for DCC track input, 2 for a motor connection ( not needed for a function only decoder, and 3 wires for some Marklin /trix motors )

And then a common positive terminal and a low- active terminal for each hardware function output eg forward  lights  reverse direction lights,  separate tail lights, cáb lights, ditch lights, warning lights...  And 2 for a loudspeaker.   Stay alive components maybe external to the decoder and need 2 or 3 wires or solder pads. Servo outputs are available on some decoders ( used for opening coach doors or raising pantographs, for example... So +5v 0v and a signal line for each ).  Some decoders may offer the 'same' function as both the 'pull down active low' and duplicated as a low voltage logic / led levél. Some others now offer 'active high' too by which I  mean that eg an led can be connected up to the blue +ve (with resistor) and another to a 0v pad.... So that the 1 physical function can toggle 2 sets of light s on/off.   Older NEM / morop ? Standard connectors may have 6 8 or more pins whilst others make us of a 22 pin format and use some of the pins. Eg 18, 21 ...

 

( I have just received some dcc decoders intended for use with opendcccar control of Faller-type vehicles... And these have 17 ! Outputs to cope with head tail side lights and turn and brake indicators... Plus sound option and motor... They recommend using a larger, early Faller lorry for a first installation attempt.)

 

[Art Dent]

12 hours ago, tigerburnie said:

So let's pretend I have decided on my controller and the track is wired up, bearing in mind my prime reason for contemplating the leap to DCC, just how many pins does a decoder need, I hadn't realized it could vary from half a dozen to near two dozen, is there a benefit if it has more pins, or is this down to which chip manufacturer you choose?

 

All depends on what you want to be able to do.  E.g. simple headlight (or front marker lights) plus loco tail light which switch according to loco direction just need 1 function - which is always assigned to f0.

 

If you want different day-time running marker(s) and headlight plus tail light and also night-time running marker(s) and headlight plus tail light(s) you need two functions.  If you want switchable tail lamps (so that they show when the loco is running light but not when it is part of a train) you'll need four functions.

 

In reality it boils down to what kind of interface the loco has, 6-pin (NEM 651), 8-pin (NEM 652), 21-pin MTC (usually Bachmann diesels) or the newer Next18 and PluX 22 (plus the sub-species PluX16, PluX12 and PluX8).

 

Different decoders by a manufacturer are often offered in several different interface formats - so you will often find a 6-pin, 8-pin and 21-pin variant of the same decoder.

 

For a loco with no lighting and no sound it only needs four connections - track input (from L and R) and motor output (to L and R).

 

This brief DCCWiki article explains (at least partially) functions (it is very brief however) > Link

 

There was originally only the headlight function F0, then F1-4 were added, then F5-12 (command stations often only implementing up to F8), and finally F13-F28 (command stations often implementing only up to F20).

 

Command stations will often treat each of these groups slightly differently, especially with respect to refreshing them.

 

These additional functions allow you to turn the sound on or off (sound decoder fitted locos with speakers), have additional lighting effects - such as Mars lights, ditch lights, cab lights and third-rail collector-shoe arcing, working pantographs (raising & lowering), smoke units - and so on.  It all depends what you want your model to be able to do - above and beyond simple motor control.

 

Art

Edited March 7, 2019 by Art Dent
Adding the missing link

[Nigelcliffe]

23 minutes ago, Art Dent said:

 

All depends on what you want to be able to do.  E.g. simple headlight (or front marker lights) plus loco tail light which switch according to loco direction just need 1 function - which is always assigned to f0.

 

 

Some clarification here needed, what you've described could be two functions or one, depending on precise reading, or mis-reading.

 

A single front light, which can be directional (ie. only works in forward direction) needs a single function output.    If, at the same time, someone also wires a tail light to the same wire, so it switches identically, that that's the same single function. 

 

But, a front light at one end (optionally tied to its matching tail light at the other), and a second front light at the other end needs two outputs so they can work independently (ie. one works in forwards, one works in reverse). 

 

 

 

10 hours ago, Phil S said:

To expand upon WIM's answer .....

For hardware functions, then each output requires a connection to the outside world (loco) from the decoder .

so 2 wires for DCC track input, 2 for a motor connection ( not needed for a function only decoder, and 3 wires for some Marklin /trix motors )

And then a common positive terminal and a low- active terminal for each hardware function output eg forward  lights  reverse direction lights,  separate tail lights, cáb lights, ditch lights, warning lights... 

 

 

The "common positive" can be achieved without a decoder output.  Instead connect the common positive on the lights to one of the track pickups.  The result is half-wave rectified power, but it will work fine for 95%++ of decoders on sale, and is fully documented in many decoder maker's manuals.    It is the way that all locos fitted with a 6-pin decoder socket are wired.

 

 

 

- Nigel

 

 

[tigerburnie]

The locos I have that are DCC fitted is a Hornby B1, I have DCC ready  Hornby 9f, 8f and Black 5, the tender driven older locos will not be upgraded and will remain on the GC layout for now( a mix of Hornby and Bachman) and the kit built V2 will become a static model.

I was looking at locos for sale and there are few with the sound and DCC already fitted, so I would be buying locos that I will be adding units to and just wondered if the number of connections equated to the number of inputs. Lights were not something I had given much thought to, sounds in particular would be the main connection space I would be wanting to improve the realism.

The shopping list will include A1, A3 and A4 and V2 and O1 steam locos, I would be adding a Deltic in early '60's livery to the group eventually.

[John M]

12 hours ago, tigerburnie said:

So let's pretend I have decided on my controller and the track is wired up, bearing in mind my prime reason for contemplating the leap to DCC, just how many pins does a decoder need, I hadn't realized it could vary from half a dozen to near two dozen, is there a benefit if it has more pins, or is this down to which chip manufacturer you choose?

DCC ready locos are fitted with a decoder socket, which basically determines the number of pins and available functions on a particular loco. Traditionally American outline locos are/were fitted with a standard 8 pin NMRA (National Model Railroad Association) socket, a 21 pin socket tends to be used for European Models.

 

The major manufacturers produce chips to suit particular  rtr locomotives and more generic chips with a choice of different plug types and decoders with leads that can be hardwired into locos that do not have a decoder socket.

 

Personally I find an 8 pin decoder adequate to control speed and direction, directional headlights and basic sound functions such as whistle and bell.

 

 

 

 

[Phil S]

1/ Agreeing with Nigel's observation of my omission from what had grown to a long reply listing the hardware connections which might occur:

That is why I did not specify the connections as 'pins' - but the text included reference to pads or contacts  ...   agreed it can reproduced outside,  as a virtual version of the on-board node...and is for 6-pin connectors, as you say  [ or giving those lights power only 50% of the time when connected to a rail] .  I thought what was intended a s 'short answer'  had grown enough already 8-)  ... and in fact has missed out the idea of software-only functions not requiring a contact, which....

2/ RE SOUND FUNCTIONS

My original intent in my reply was meant to include that, SOUND FUNCTIONS only required the common loudspeaker connection (or SUSI interface to an add-on sound module - found on some continental silent decoders).  ANY NUMBER of SOUND functions can be included in the DECODER's MEMORY/software without adding any extra hardware pins or contacts. - these are created by whoever created the sound=files

in conjunction with the capabilities created by the manufacturer.   Some have multiple sound capability at the same time - but these are mixed together digitally on board the decoder, and do not require extra contacts there ....maybe just more buttons on your controller though !!

[Art Dent]

42 minutes ago, Nigelcliffe said:

Some clarification here needed, what you've described could be two functions or one, depending on precise reading, or mis-reading.

 

A single front light, which can be directional (ie. only works in forward direction) needs a single function output.    If, at the same time, someone also wires a tail light to the same wire, so it switches identically, that that's the same single function. 

 

But, a front light at one end (optionally tied to its matching tail light at the other), and a second front light at the other end needs two outputs so they can work independently (ie. one works in forwards, one works in reverse). 

 

Thanks Nigel for the clarification.

 

Where I was coming from was that bog-standard kit locos (eg. Bachmann Diesels) have the front headlight (or headcode) wired to the loco's rear lights at both ends, so with the lights on they will change as the loco direction is reversed - all controlled from f0.

 

42 minutes ago, tigerburnie said:

The locos I have that are DCC fitted is a Hornby B1, I have DCC ready  Hornby 9f, 8f and Black 5, the tender driven older locos will not be upgraded and will remain on the GC layout for now( a mix of Hornby and Bachman) and the kit built V2 will become a static model.

 

Hi Tiger,

 

Steam locos are generally more difficult to wire with directional lighting due to the very cramped space inside these locos.  Diesels usually fare better in this respect as their 'boxy' shape and cabs at both ends usually means there is ample space to fit DIY lighting rigs or proprietary lighting kits as sold by the likes of Express Models.

 

42 minutes ago, tigerburnie said:

I was looking at locos for sale and there are few with the sound and DCC already fitted, so I would be buying locos that I will be adding units to and just wondered if the number of connections equated to the number of inputs. Lights were not something I had given much thought to, sounds in particular would be the main connection space I would be wanting to improve the realism.

 

If you are looking at DCC Sound locos, they will already have the requisite decoder and speaker fitted.  Your only choice then would be to swap (say) a 4-function LokSound decoder for a decoder with more functions - e.g. a Zimo MX645 with 10.

 

Hope this helps,

 

Art

Edited March 7, 2019 by Art Dent

[tigerburnie]

Looking around on youtube and then what is on the market, the Bachman Dynamis looks like good value and also looks suitable for my purpose, ie not a  lot of trains running at once and has enough controls to be able to run with sound on my predominantly steam railway, any thoughts from those who use or have used this system? I like the fact that it is modular and it can be upgraded if required.

[Nigelcliffe]

19 minutes ago, tigerburnie said:

Looking around on youtube and then what is on the market, the Bachman Dynamis looks like good value and also looks suitable for my purpose, ie not a  lot of trains running at once and has enough controls to be able to run with sound on my predominantly steam railway, any thoughts from those who use or have used this system? I like the fact that it is modular and it can be upgraded if required.

 

Run away.   Its an ancient design, never that good in its day.   There are MUCH better alternatives. 

 

 

[tigerburnie]

Any specific reason Nigel, what are it's major failings?

[Ravenser]

26 minutes ago, tigerburnie said:

Any specific reason Nigel, what are it's major failings?

 

Although not a user and not of Nigel's terchnical capabilities and knowledge, I'm aware of 2 failings:

 

- It won't read back CVs (unless you buy an expensive upgrade box)

- The base station communicates with the layout by infra red. This is notorious for losing the signal - meaning a briefly-uncontrollable layout

[tigerburnie]

Thanks Ravenser, I have no knowledge of these things, so have to ask, I am trying to do this right first time, but on a budget, retired so no longer in a position to buy the best on the market, like have done with expensive hobbies in the past.

[Ravenser]

If the current draw from DCC Sound is manageable , then the NCE Powercab would be an excellent system .

 

The only possible issue is that it only delivers  a maximum 2 amps

 

I don't think you need computer control on a layout this simple

[tigerburnie]

Well after seeing James Mays program, it would seem all I will need is a vent van and single bit of track lol.

[Andymsa]

14 hours ago, tigerburnie said:

Well after seeing James Mays program, it would seem all I will need is a vent van and single bit of track lol.

 

Not if you want a cat

meow

Edited March 8, 2019 by Andymsa

[Sir TophamHatt]

On 06 March 2019 at 22:04, tigerburnie said:

... bearing in mind my prime reason for contemplating the leap to DCC, just how many pins does a decoder need.

 

Nearly half my locos don't have any functions - only forward and back.

I bulk bought a load of 8-pin decoders to hardwire them in (none had sockets).  Zimo or Lenz Silver + v2 - both around £20 each.  When I first started, I couldn't see anything telling me 8-pin wasn't the best for what I needed.  You can get 6-pin decoders but they're more complicated to fit (I cut the plug off most my decoders to hard wire them in).

 

With some of the locos, I wish I had fitted a socket.  Although saying that, I doubt I'll ever be taking them out.

 

Now I give a bit more consideration whether I need/want a socket or not.  A Bachmann Thomas for example will never do anything more than forward or back.  My Bachmann Voyager however, I may wish to fit sound in the future, so I fitted sockets.  At 99p from ebay, I consider the sockets to be a very good price.

[tigerburnie]

Have modified the layout design as the previous didn't seem to work for delivery and collection of wagons, still based on the village where I live, this mimics the track bed as it was in the 1950's, but I have re-built the up platform and will re- install the passenger bridge as I had a referendum(we seem to like them up here) and have re-instated passenger traffic(something that might be a good idea today).

With fiddle yards at each end thoughts of a removable bridge where the access door is, continuous loops could well be installed.

 The proposed home is in the old summer house(TOSH, I'm good at talking tosh) which is 14 feet by 10 feet, with the main layout being along the back 14 foot wall, with sound being planned for all the locos running, primarily steam, but with the odd oil burner for the 1960's part of the era(1955 to 1965). The 10 foot "ends" will accommodate the sidings/storage and could even come round the corners slightly to the "bridge" lift out section, by the double doors which will be 4 feet long, double track section.

 

[tigerburnie]

Well as no one has pointed out a rash of problems for this proposal, it may actually end up like this(roughly), the only isolation I was planning was between the points connecting the two through lines, but thinking about it, maybe they won't be needed either.

[Art Dent]

Yes, you'll need to add insulating fishplates (also known as insulating rail joiners or IRJs) on both rails as shown here ...

 

 

The above is just an example.

 

This practice should be followed whether using DC or DCC, especially when using electrofrog points.

 

The IRJ labelled '1' could be omitted.

 

Regards

 

Art

Edited March 9, 2019 by Art Dent

[tigerburnie]

Is that to reduce the shorting problems with points Art, I have read Peco points can have a frog problem, someone on youtube suggested using insulating connectors(something I have installed on my DC layout already).

[Art Dent]

Just now, tigerburnie said:

Is that to reduce the shorting problems with points Art, I have read Peco points can have a frog problem, someone on youtube suggested using insulating connectors(something I have installed on my DC layout already).

 

Yes. The gap between the 'V' rails in the frog are quite close and older (wider) wheels may bridge the gap and cause a short.

 

The IRJs indicated in my diagram above, together with a wire that connects to the 'V' rails and switches polarity when the frog is thrown, sorts this out.

 

Art