DCC Decoders - 8 pin & 21 pin

[GordonBigBoy]

I think I have learnt a little about the differences but just want to confirm from a beginners perspective. I believe 8 pin allows for some speed settings, double heading and lights, and a 21 pin adds to this an ability for sound, more defined speeds,

 

smoke and fuel sim and no doubt a load of other advanced stuff that I have not focused on yet.

 

I have the following questions:

 

1. If I buy a loco that is DCC ready with a 21 pin slot, can I assume that the loco has (at least) the added ability

 

to make sound or do I have to add speakers to the loco?

 

2. I see that you can buy an adapter that allows you to fit an 8 pin decoder into a 21 pin slot. Why would you do this other than to save the £12 difference in the cost between the (Hornby) decoders?

 

3.

 

I see the Sapphire digital loco decoder has an adapter " This decoder comes with a wiring harness and a 8 - 21 pin adaptor". Does this mean you can fit a Sapphire into an 8 pin slot? I am not sure why you would you want to do that - confused?

 

The question

 

is really all about buying DCC ready loco's. I am guessing 21 pin slots are preferable at the right price, but expect to pay an additional £12 for a 21 pin decoder. Advise appreciated.

[Rog RJ]

1. The only difference between 8 and 21 pin decoders is the plug. Just because it has a 21 pin plug doesn't mean it has any more capabilities than an 8 pin decoder. If you want sound you need to buy a sound decoder (either 8 or 21 pins to suit the loco

 

or "wires only, IE no plug fitted"

 

2. Some decoders are only available as 8 pin versions, or you may have a stock of 8 pin decoders, or 21 pin decoders are unavailable - it happens.

 

3. For flexibility, as in 2.

[Rog RJ]

I addition to the above, 22 pin decoders are now starting to become available. These have a new plug that is different to the 21 pin. 22 pin sockets in locos will be able to accept 6, 12 or 22 pin decoders. See http://www.dccconcepts.com/index_files/DCCdecoderfunctionsdesc.htm

[Rog RJ]

Additional.

There is also going to be a 16 pin plug available, which you are more likely to come across than the 12 pin version.

The 22/16/12/8 pin system are known as Plux connectors.

[GordonBigBoy]

Rog (RJ) said:

I addition to the above, 22 pin decoders are now starting to become available. These have a new plug that is different to the 21 pin. 22 pin sockets in locos will be able to accept 6, 12 or 22 pin decoders. See http://www.dccconcepts.com/index_files/DCCdecoderfunctionsdesc.htm

Rog,

the link you pointed me to is really excellent - many thanks. I now know there is little difference between 8 pin and 21 pin which really surprised me.
I have learnt there are many kinds of 8 pin decoders and some are better than others evidently. It seems

to me to be sensible for a beginner to stick to one type so that programming is the same for each loco. A loco that is DCC fitted means you don't get to choose. A DCC Ready Loco allows you to choose your favorite decoder and you fit it yourself. If I buy a

21 pin DCC Ready loco (of which there are a few around at bargain prices - hence this thread) I now know I can use a simple adapter to fit an 8 pin decoder into the 21 pin slot. And lastly I have importantly learnt that sound is very expensive circa £100+

per locomotive. You can buy sound modules (with specific sound files loaded) with 8 pin or 21 pin decoders as part of a complete package with a speaker. Plan for a lot more ££ if you get the supplier to fit it.

Final thing I need to ask is: what are

the opinions of others on what is the best or favored 8 pin decoder - is there another forum where I could ask this question, or a magazine on-line that has done a review? (I am in Thailand so no model shop to visit for advice until my UK trip in September)

Many thanks.

[GordonBigBoy]

For example it seems the Hornby R8249 DCC 8 pin decoder does not support BACK EMF

[Rog RJ]

As far as I am aware, all Hornby decoders have had back emf as standard, even the first versions of the old R8215 although there was no way of adjusting it or switching it off.

 

If you look at the instruction sheet for the R8249 decoder https://www.hornby.com/filelibrary/download/?FileID=137

 

you will see that CV10 controls the back emf cutout point.

[hosh]

Rog (RJ) said:

As far as I am aware, all Hornby decoders have had back emf as standard, even the first versions of the old R8215 although there was no way of adjusting it or switching it off.

This piece of info goes well

with the other thread about having dcc fitted locos - a bad idea.

[Fishmanoz]

Gordon BB, to answer your question on the best decoder, virtusally all DCC equipoment including decoders are made to meet the NMRA (National Model Railway Association) DCC standard. Consequently, no one decoder is better than another although not all have

 

all of the features allowed in the standard. Look at Hornby's information on the R8249 and the Sapphire to see the features included in them. As said above though, back EMF is a pretty standard feature that will be found in them all.

Onr exception to the

 

NMRA standard, which is acknowledged by Hornby, is the Select - it is made as an entry level budget controller and doesn't meet the standard.

[GordonBigBoy]

Rog (RJ) said:

As far as I am aware, all Hornby decoders have had back emf as standard, even the first versions of the old R8215 although there was no way of adjusting it or switching it off.

If you look at the instruction sheet for

the R8249 decoder https://www.hornby.com/filelibrary/download/?FileID=137 you will see that CV10 controls the back emf cutout point.

Thanks for the correction Rog and apologies to Hornby. In fairness their website description does not mention

back EMF for the R8215, but it does specifically mention back EMF capability in the first line description of the Sapphire!

[GordonBigBoy]

Fishmanoz said:

Gordon BB, to answer your question on the best decoder, virtusally all DCC equipoment including decoders are made to meet the NMRA (National Model Railway Association) DCC standard. Consequently, no one decoder is better than

another although not all have all of the features allowed in the standard. Look at Hornby's information on the R8249 and the Sapphire to see the features included in them. As said above though, back EMF is a pretty standard feature that will be found in them

all.
Onr exception to the NMRA standard, which is acknowledged by Hornby, is the Select - it is made as an entry level budget controller and doesn't meet the standard.

Hi Fishman, thanks for the further info - I now feel more confident about

decoders generally. The other thing I learnt yesterday is that some locos (if I understand correctly) consume more amps than others and this apparently can fry some of the lower amp rated decoders so I need to take care there when selecting and matching decoder

types me thinks?

Yup I noticed that the Select is not NMRA standard (and apparently cannot be easily hw or sw upgraded); this influenced my decision to buy the Elite.

[Fishmanoz]

Gordon BB, you'll find standard decoders like the R8249 have sufficient output to handle all modern locos. It's only when you go for older locos pre-1990 that you find they use more current.

[Gregd99]

If you need more puff for some older locos the 8245 has more current (and function) capability than the 8249. It is also a bit bigger.

 

If you google stall test you will find some info on current requirements. Personally, I think a hard stall, ie

 

the wheels jammed stationary with full power applied, is extreme. running a locos against buffers with the wheels slipping is more realistic as a max load.