One engine, two decoders

[MisterBeasley]

This was touched on briefly a few weeks back, but I'd like to get some clarification from anyone who has done this already.

I've got a Bachmann Peter Witt trolley that came with a Bachmann decoder.  I've added a Digitrax SFX0416 sound-only decoder, and set them both to respond to address 44, the number on the trolley's nose.  I can run the trolley fine, toot the whistle and ring the bell, but I've found that I can't read and set CV's.

Someone mentioned the option of setting different 4-digit addresses for each of the 2 decoders.  I assume that the decoders could then be "decoupled" by enabling 4-digit addressing, which would let me program each decoder individually.  Hopefully, I could then return to 2-digit addressing and the decoders would once again respond as one.

Since I have had trouble setting CV's, I'm not sure that I can enable 4-digit addressing once the decoders are coupled together.  I have been able to set some CV's, though, so this may work.

Do I have the concept right on this?  Are there any pitfalls I'm not seeing?  Any other hints that might make life easier?  Incidentally, I would rather not do this with MU-ing.  I have enough engine numbers in the stack as is.

Thanks in advance.

[jfugate]

You've got the basic concept down ... but I've generally done it the other way: same 4-digit address, different 2-digit address.

Let's say I have loco 4411 and it has a motor decoder and a sound-only decoder in the same loco. I will set the addresses as follows:

Motor decoder

• Long address: 4411
• Short address: 11 (last two digits on the cab)
  

Sound-only decoder

• Long address: 4411
• Short address: 03 (default new decoder address)
  

I generally run with the long address of 4411, so both decoders respond to the same commands as a unit. But if I need to separate the two decoders to program a specific CV in only one of the two decoders, I will set the decoder to two digit addressing (CV29) and know that the motor decoder will always be the last two digits on the cab, and the sound-only decoder will always be address 03.  Once I'm done with the CV changes, I will set the loco back to 4-digit addressing and the two decoders will work as one again.

Using address 03 for the sound-only decoder works because you don't want to run any address 03 locos on your layout ordinarily -- that's the default decoder address for all decoders from the factory. It's too easy to accidentally screw up the settings of another loco on your layout if you have one that's also using address 03 as its permanent address.

You should always consider address 03 as very temporary for programming convenience and not *leave* any locos at that address after you are done programming their decoder.

Does this make sense? 

[UpNorth]

Only problem I see with this configuration is resetting motor decoder to defaults will cause a problem requiring you to physicaly isolate one decoder from the other so you can talk to one of them. 

Solution I propose  is setting motor to short add 11 and sound to short add 12 or 10. Use 4411 as the shared long add. Or  use 44 for the motor decoders short add and 11 for the sound decoder short add. 

From experience, this will save you from having to play with wiring in case both decoders end up on the same short add by accident or default.  

[jfugate]

As long as you use 4 digit addresses for all your locos and you don't ordinarily run anything in short address mode, you can use any 2-digit addresses you like (except 03), since nothing else on the layout will match it.

The point about using address 03 for the sound decoder address is very valid ... if you ever need to reset the motor decoder, you will end up with it back at address 03 as well, and then you're sunk because both decoders will have the same short and long addresses. The only way you will be able to address them separately is by opening up the shell and physically pulling out one of the decoders.

I want the addresses to be easy to remember, so I like to use the last two digits of the cab as the motor address -- 11 in my example. I'd be inclined to just add one for the sound decoder address -- 12 in this case. Since you'll reset them back to the 4-digit address of 4411 in a few minutes once you're done with the separate CV programming, this method of picking the decoders' 2-digit addresses should work fine.

[MisterBeasley]

It's been a while since I read my Lenz manual, but as I recall, the base station uses address 00 and the first throttle uses address 01, and in my case, the second uses 02.  Are these part of the same address sequence as the locomotives, or is this different because it's on the bus side rather than the track side?

Not really an important question operationally, but if there is a conflict between a throttle addressed as 01 and a potential locomotive also addressed as 01, sooner or later, someone will run into it.

By the way, the trolley itself is number 44, so I'd rather use the 2-digit address to control it and pick a couple of 4-digit addresses for programming purposes.

 

[MisterBeasley]

As I've been thinking about this, I'm not sure how this works.  If I read/write CV's on the programming track, I don't have to enter an address on my Lenz system.  Similarly, when I'm working with the PR2 programmer, it doesn't ask for an address.

So, if I've got 2 differently-addressed decoders on the programming track, how do I only talk to one of them?

[Phoebe Vet]

This is not an aswer, but rather another question, because I do not know the answer.

Can the two decoders be given different addresses and then treated like a consist?

I know Digitrax intends for the two decoders to be programed like they were one so that the sound will synchronize with the motor functions, but  if you do it that way you cannot read back the values.  You can, however still, assign the values.

[CSX Robert]

It's been a while since I read my Lenz manual, but as I recall, the base station uses address 00 and the first throttle uses address 01, and in my case, the second uses 02. Are these part of the same address sequence as the locomotives, or is this different because it's on the bus side rather than the track side?...

The throttle bus addresses are seperate from the decoder addresses and will not cause a conflict if they overlap.

As I've been thinking about this, I'm not sure how this works. If I read/write CV's on the programming track, I don't have to enter an address on my Lenz system. Similarly, when I'm working with the PR2 programmer, it doesn't ask for an address.

So, if I've got 2 differently-addressed decoders on the programming track, how do I only talk to one of them?

This method is strictly for operations mode programming(some refer to it as porgramming on the main because the engine stays on the layout instead of being moved to the programming track) where you have to give the address of the decoder that you are programming.

If you have two decoders in one engine, you can not use the programming track to write to the decoders seperately unless the deocders support the decoder lock feature, which I don't think the Bachmann decoders do. This also brings up another point - this method lets you program the decoders seperately, but you still will not be able to read the CV's back, because you have to do that from the program track.