DCC Enabled dummy cars (lights etc) code change

[AddlestoneP]

Hi Everyone,

I think I am being thick.

I have had my APT re-pwered and a Class 101 converted to DCC, both with lights in the non pwered parts. I have changed the decoder number to four digits from the default '3' but when I ask Railmaster to change the codes for the non powered cars, two DVT's on the APT and one on the DMU it gives me an error message and says that it cannot read the CV's.

I understadn the reason for this is that ther system requires the motor to register a load against the identification of the decoder.

How do I solve this?

All help most welcome.

Many thanks,

Howard

www.addlestoneparkway.co.uk

[Rog RJ]

There are 2 simple options you can use.

Method 1 is to put both the powered car and the unpowered car on the programming track at the same time and do the programming.

Method 2 is to take the decoder from the dummy car and program it in the powered car and then put it back in the dummy car.

[Graskie]

I had this sort of problem with a Bachmann 2 car class 108 fitted specially with sound decoder in the power car and the original left in the dummy car for its interior and directional lights.

I changed the power car and, hopefully, the dummy car to the same 4 digit ID. The power car was no problems but I couldn't set the dummy car ID to the same ID. I tried reading its current ID, which was apparetly 03, same as the power unit, when I received it all. No ID reading on my Elite or RM.

I eventually solved the problem by giving each unit the same double digit ID and it worked. Could be that the dummy car and carriages are only capable of being set to 2 digit IDs. After all, they only work the lights, don't they? And there was no electrical connection between my 2 units.

[AddlestoneP]

I shall try two digits, thank you

[poliss]

Bromsgrove models suggest placing both cars on the programming track and then programming the trailer car first.

[Graskie]

Do you mean placing both cars together, poliss, or separately, on the programming track? I tried all sorts of combinations like that, but to no avail. I just couldn't read an ID number from the trailer car, whatever I did, but it  did accept a 2 digit ID in the end, which I then had to match for the drive unit to achieve the same combined ID.

[poliss]

Here's the page Graskie.

http://www.bromsgrovemodels.co.uk/BachmannCl108DCCInstr.htm

To read the decoder in the dummy car I expect you'll need to have a 50-100 ohm resistor in series between the blue wire and any of the light function wires.

[Fishmanoz]

Sorry, but you lot seem to me to be talking through my hat and as you are also standing on your heads from my perspective, I'm having trouble understanding your logic.

So what do I think is going on? Well, the fundamental problem for the dummy car, and confirmed by Brian Lambert at http://www.brian-lambert.co.uk/DCC.html#OO is that some decoders don't like being programmed or being read without a load on their motor connections, the orange and grey wires. To fix this, you have to put a load across them and Brian suggests a 100 ohm resistor. Loads on function wires will not solve this to my knowledge, so I don't think your suggestion works poliss. By the way, the 8249 is not such a decoder and will clearly program without a load. And it will also make no difference at all whether you are trying to program a 2 or a 4 digit ID, I think you were just lucky when you did this Graskie. 

Secondly, you can't put both power and dummy cars on the programming track and expect to program the trailer before the dummy. Once they are both on the track, anything you do will apply to both. That's what a programming track is about after all.

So, to me, there are a couple of ways to do this. For a start, given the dummy decoder wouldn't program, you will either have to put the load of a 100 ohm resistor on its motor connections, or you could swap it for an 8249 and that won't be necessary. Now you can program the same ID into both either separately or at the same time, it doesn't matter, it only matters you put the same ID into them. If both together, you may have to be careful with other function programming as the sound decoder and the non-sound will have different functions after all.

Now for directional lights, they should just work, except you may have to check if installed in a non-DCC ready dummy car that you don't have to program CV29 for reverse running to make sure they show the right way around, depending on how they have been wired. This will have been accounted for with a DCC ready though.

Now, do I have this right or is it me talking through the hat?

[poliss]

I took the instructions about the resister directly from the manufacturers website Fishy. As it was a function only decoder you can't put a load on the motor connections.

[gilbo2]

Interesting comments on the R8249, I've always found they need a dummy load too in this situation

[Graskie]

Oh dear, I feel like a dummy now, but my simplistic solution sounds much easier, but, of course, only if it applies to the poster's situation. I don't think I was just lucky, Fishy. I never am.

[Fishmanoz]

Ok, apologies for 2 hat moments. Hadn't come across that detail on function only decoder before needing a function load, but motor load still applies for standard decoder. And thanks dg, thought I'd seen others not needing a load for the 8249. 

Another way is of course to swap the dummy car decoder into the power car for programming, although that will not be possible if sound decoder fitting in the power car has used a different sized socket like 21 pin.