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How Many Decoder Pins Do I Need?


Sir TophamHatt

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The least number of pins a DCC decoder can have is 4. Two wires to the motor and two to the pickups. Hornby use these in some of their models. Example.

Six pin decoders are common in n gauge models. The 2 extra pins allow for 2 functions as well as the motor control.

Eight pin decoders were the standard for some years in 00 models allowing for 3 functions as well as motor control. These have a blue wire which is the common positive connection for the function outputs. The blue wire is not included in 6 pin decoders as these use the pickups for the common.

As more and more functions and sound were added to models a larger number of connections was needed and so the 21 pin decoder came along. And so it goes on with new standards popping up........

 

There are some physically very small decoders available from some makers such as Zimo and CTX.

 

Obviously, you buy a decoder to match the loco. No good buying a 4 pin decoder if the loco has a 21 pin socket. If the loco doesn't have a socket fitted then you need to solder a decoder in yourself or get someone else to do it for you. This is usually called hard wiring.

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Yeah, I'll have to hard wire all my locos as I have none that are DCC ready at the moment.

 

So I don't want to buy a smaller decoder when in the future I might need a few more features - thus having to physically cut it out and butcher in a new one.

 

However, thank you for your detailed answer :D

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If hardwiring, look for decoders that come with wires attached, usually without a plug fitted. There are lots of these around.

If the decoder you want only comes with a plug attached, it can always be snipped off.

Direct fit decoders (pins/socket on the decoder board itself) are not suitable.

 

Other than hard-wiring in a decoder, another option you have with locos that are not DCC Ready (i.e. no socket fitted), is to fit a socket yourself (or have someone do it for you).

Provided there is suitable room for a socket and any decoder that's plugged into it.

 

By installing a socket, direct fit and those with plugs on wires can be used.

Also it will allow decoders to be easily changed in the event of a failure, or if there's a need or reason to upgrade or change decoder.

Buying a socket will add slightly to the cost though, if that matters to you?

 

Alternately, if just hardwiring, one method I have seen used, is to hardwire to an intermediary piece of circuit board, to which the loco wires are permanently fixed.

Again, available space has to be considered.

 

 

.

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Yeah, I'll have to hard wire all my locos as I have none that are DCC ready at the moment.

 

So I don't want to buy a smaller decoder when in the future I might need a few more features - thus having to physically cut it out and butcher in a new one.

 

However, thank you for your detailed answer :D

 

There is a further complication. The number of pins (or the physical size of the decoder) is not necessarily matched by the number of Function Outputs or other features.

 

For example, a Hornby 8 pin decoder might have 3 function Outputs, but a top flight decoder like a ZIMO 8 pin decoder will have up to 10 Function Outputs. A cheap 21 pin decoder of the types mentioned above may, on the other hand, have, for example, a few as 4 Function Outputs, several of the pins being unused dummies to make up the numbers.

 

Future expansion potential is quite different in each case and is related to the decoder specifications not the numberof pins on the interface, or the number of wires provided.

 

Kind regards,

 

Paul

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It is well worth considering fitting a socket rather than hard wiring. The Zimo ADAPLU board is quite excellent for this, especially if you might want to add extra functions or sound later.

 

This is where the PluX socket is ideal because you can fit a 22-pin socket, but can plug in any PluX decoder, so to start with you might just use an 8-pin or 12-pin motor only decoder with a few functions (not sure that anyone makes an 8-pin PluX yet!), and then later perhaps swap it out for a 16-pin or 22-pin, or even perhaps a sound decoder.

 

Decoders with wires on are usually more expensive than direct plug-in where alternatives are available so that will offset the cost of buying the board a little.

 

You can start with an excellent entry level decoder like the Zimo MX600p12 with just four functions (£19) and upgrade all the way to a Zimo MX645p22 with ten functions and sound (£92) all in the same socket.

 

Other sockets are often bulkier and limit you to far fewer functions:-

  • 6-pin NEM651=2 functions
  • 8-pin NEM652=2/3 functions
  • 9-pin jst=4 functions
  • NEM662 NexT18s=6 functions + sound
  • NEM662 NexT18=8 functions
  • NEM660 MTC21=8 functions + sound
  • NEM658 PluX=10 functions + sound
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Yes you might, for lights, firebox glow, etc..

Not in my world. Firebox glow is seldom seen except when the stoker is actually feeding the fire or similar. It should not be visible most of the time as the firebox door is closed. Most UK steam locos did not have lights you would ever see. No headlight, and any class lights were powered by glow-worms. Elsewhere in the world steam locos do have lights worthy of the name. UK steam did not.

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Not in my world. Firebox glow is seldom seen except when the stoker is actually feeding the fire or similar. It should not be visible most of the time as the firebox door is closed....

 

Used on a momentary function (non-latching), the glow effect can be triggered briefly to give the effect you describe.

(rules out almost all US systems, which only have one non-latching function available)

Appropriate sound effects can be linked to this, if desired.

 

The most recent firebox glow LED set-ups use 2 or 3 colours flickering at different rates to give a more realistic impression.

 

 

 

.

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Not in my world. Firebox glow is seldom seen except when the stoker is actually feeding the fire or similar. It should not be visible most of the time as the firebox door is closed. Most UK steam locos did not have lights you would ever see. No headlight, and any class lights were powered by glow-worms. Elsewhere in the world steam locos do have lights worthy of the name. UK steam did not.

 

But we're not really talking about your world are we. As for the class lights, I agree, except that the brightness is simply a matter of using the right resistor for the LEDs. They can be as dim as you like. Also - where did the OP say anything about just using decoders on steam locos?

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NexT18 specification is not significantly smaller than the equivalent PluX sizes, and PluX decoders are often smaller than NexT18 spec anyway. It is a standard that is obsolete before it is born, but it looks like loco manufacturers are going to misguidedly fit it to locos anyway the same way that MTC21 has been supported by Hornby, Bachmann, etc. in the face of a much better alternative.

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  • 3 weeks later...

Sorry to drag this up again.

 

So just to make sure - I can fit a socket, which is a standard size, then upgrade the chip in it to be 4, 8, 21 sockets in the future if I need more?

 

I am looking to convert around 10 trains, all uni-formally if possible (not really possible, but I can hope!), so all the trains have about the same features and stuff.

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Sorry to drag this up again.

 

So just to make sure - I can fit a socket, which is a standard size, then upgrade the chip in it to be 4, 8, 21 sockets in the future if I need more?

 

I am looking to convert around 10 trains, all uni-formally if possible (not really possible, but I can hope!), so all the trains have about the same features and stuff.

No the plux comes in different number of pins but the rest what you start with is all you get

so if using oo mainly the 8 pin has been used which gives you a max of 3 outputs without using direct wires (outside of socket)

hope that helps

trevora

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Sorry to drag this up again.

 

So just to make sure - I can fit a socket, which is a standard size, then upgrade the chip in it to be 4, 8, 21 sockets in the future if I need more?

 

I am looking to convert around 10 trains, all uni-formally if possible (not really possible, but I can hope!), so all the trains have about the same features and stuff.

 

The PluX range has different sized decoders that are compatible with PluX sockets as long as the socket has more holes than the decoder has pins - sockets can be 8-pin, 12-pin, 16-pin or 22-pin. Entry level 4-function decoders tend to be 12-pin, small sound decoders and 6-function motor only decoders with stay alive are 16-pin, and full featured decoders are 22-pin. If you have room for a 22-pin socket (typically H0-gauge and above), fit it and you can fit whichever PluX decoder in that you like. If you only have room for a 16-pin socket (N-gauge sized typically) you can fit any PluX decoder 8-pin to 16-pin.

 

All the other decoder sockets are fixed size - NEM651 6-pin, NEM652 8-pin, jst-9 9-pin, NexT-18 and NexT-18S 18-pin, and MTC-21 21-pin.

 

PluX, Next-18(S) and MTC-21 are reasonably space efficient, all the other connectors tend to take a lot of room and have limited functionality. PluX on the whole is the most space efficient for all socket sizes based on what is currently available if you trade functionality against size (Next-18 might be the best choice if you need an ultru-slim decoder installation - but there is only a millimeter in it).

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Okay - I see - thanks :)

 

If I was to grab this: 

 

 

DCC Lights for Bachmann Class 170 Turbostar. Ref: DCCB170W

A replacement lighting set for the Bachmann Class 170 Turbostar with day and night high intensity white headlights, marker lights and tail lights.
Requires a 4 function decoder for each power car.
Similar to the Voyager lights illustrated above.
Price: £23.95

 

I guess I would need the 4 function decoder just for the lights?  Thus, I'd need more function decoders for controlling the motor?

 

Also, is Express Model's cables (here:http://www.expressmodels.co.uk/acatalog/0_6mm_Diameter_Multistrand_cable_.html)good for connecting decoders and sockets and such to motors?

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Be aware that Express Models lighting kits, where say they have three front and two rear directional lights along with maybe cab lights tagged on, may be outwith the function load capability of your decoder. I have fried the odd Hornby TTS and R8249 decoder by ignorance of this.

 

Typically this capability can be a 100 mA limit per function, with an overall decoder limit to take account of as well, and as an led can draw 20-30 mA current apiece, it pays to throw another 1K resistor in series with the blue wire to further limit the current and as a bonus it can also dim the lights a bit if the total resistive values are just right.

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Not in my world. Firebox glow is seldom seen except when the stoker is actually feeding the fire or similar. It should not be visible most of the time as the firebox door is closed. Most UK steam locos did not have lights you would ever see. No headlight, and any class lights were powered by glow-worms. Elsewhere in the world steam locos do have lights worthy of the name. UK steam did not.

The firebox glow can/should be linked to the "shovelling coal" sound so it only comes on when this plays.

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Okay - I see - thanks :)

 

If I was to grab this: 

 

 

 

I guess I would need the 4 function decoder just for the lights?  Thus, I'd need more function decoders for controlling the motor?

 

Also, is Express Model's cables (here:http://www.expressmodels.co.uk/acatalog/0_6mm_Diameter_Multistrand_cable_.html)good for connecting decoders and sockets and such to motors?

No - functions are for functions, eg. Lights, smoke etc motor control is quite different but in all the examples given in this thread is included in the same decoder ie, it both drives the motor and can operate a number of functions as well.

 

Please don't take this the wrong way, it's not meant to be patronising in any way, but, this is a big topic not really suited to a thread and the technology improves almost monthly. It would help, I think if you got a book on DCC (don't ask for a title as there are a great many) and start from the beginning. That way you will appreciate, why it came about and what it's possibilities are in relation to what you want to get out of it.

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Don't worry - you can talk to me in as much simple and child-like way as you like.  I know very little about DCC :P

 

Would the Lenz Standard + v2 controller work for the Express Models lights? (they come with 4 function outputs as far as I am aware).

 

And would fitting a resistor make the lights dimmer then?  I wouldn't know where to buy one :/  I guess I'd have to buy 100 for a few pounds from somewhere like ScrewFix?

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Probably worth getting a Zimo MX600 decoder for each end of the 170 (and one for the power car too if it is a 3-car). Similar price to the Lenz standard V2, but you are getting a Zimo with most of the Zimo features, including CV60 for function dimming if you find the resistors supplied by Express Models inadequate for your purposes (the supplied resistors are OK in my 170!).

 

If you are keen you can add some orange LEDs for the door open lights as well, Zimo has a function to turn them on when stationary and Bachmann have kindly supplied the orange lenses for them.

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Thanks :)

 

I bulk bought 10 Lenz v2's from a German website for £14 each.  Although I do have 9 steam locos to chip and a DCC ready HST I can stick the other in, so I'll have to get some more at some point soon anyway.

 

I've seen videos of the Express Models 170 lights and they do look a little over bright but I'll have to see them in the flesh before looking at resistors.

 

Just makes me a little sad I need two chips.  I would have thought the one would be able to control both sets of lights.  £40 is a lot of extra dosh but I can put it off a little while (despite already ordering the lighting kit!).

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You can buy conductive couplings, but they still have a cost and it is a lot of extra wiring.

 

If you are super-keen and don't want to do the door-open lights you can move the motorised chassis to one of the driving trailers and that will save a decoder. Probably more than £14 worth of trouble.

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