2 decoders wrong lighting

[BusDriver]

Hi all,

 I’ve had a search, but either can’t get the search terms right or just can’t find the information I need. 
I’ve just bought a Hornby class 800 and as per the instructions fitted 2 DCC chips (one per end car). I’ve put these on my test/programming track and changed the address. Everything works beautifully except the fact that when I turn the lights on they are either both headlights or both tail lights. I’ve had a play with the CV values (very much a newbie so don’t think I did it right), but can’t seem to get them to work in the correct orientation as one. 
Hopefully someone will be able to help me with a simple solution so it looks right when running. 
If it helps I use a Z21 and Lenz silver chips. 
thanks in advance

[Nigelcliffe]

Usually this happens because both ends think "forwards" is the end with the cab of the loco.  But, in use, one end has to be "forwards" and the other "reverse".

 

Fix is one of:

a - program one of the chips (not both) so its direction is reversed in CV29.  Your Z21 should help you do this. 

b - change the lighting "function map" so the lights are the other way round, generally this is CV33 and CV34. 

 

Try (a) first.

 

 

[BusDriver]

32 minutes ago, Nigelcliffe said:

Usually this happens because both ends think "forwards" is the end with the cab of the loco.  But, in use, one end has to be "forwards" and the other "reverse".

 

Fix is one of:

a - program one of the chips (not both) so its direction is reversed in CV29.  Your Z21 should help you do this. 

b - change the lighting "function map" so the lights are the other way round, generally this is CV33 and CV34. 

 

Try (a) first.

 

 

Thanks. Having spent the evening reading around, I think my issue was trying to reprogram the trailer car rather than the driving car as everything stopped working when I did that. 

Still trying to figure out how to program different CVs and what that all means, but I’m sure I’ll get there  

[Nigelcliffe]

A common issue with programming trailer cars is the lack of any "acknowledgement" signal.

 

To be "read" a DCC chip needs sufficient load on its outputs to generate a pulse back to the programming device.  In a loco, the load is a motor.  A couple of LEDs in a trailer car are insufficient load to generate the pulse.    So, the trailer car often cannot be read. 

With some systems this means "can't be programmed".   With others it can be programmed, but not read. 

 

The pragmatic way out is to put the trailer car decoder in the locomotive-car, program it alone.  Then remove decoder from loco-car, place in trailer car.  Now put loco decoder in loco-car, program that alone.  Once programmed, combine trailer and loco-car and run them on layout.

 

I can't remember what CV29 support is in the Roco Z21 applications.  Years ago, I wrote an explanation and tool to calculate CV29:
http://www.2mm.org.uk/articles/cv29 calculator.htm

 

 

There are many ways of solving issues around two decoders in a multiple unit.

 

- Nigel

[johnd]

9 minutes ago, Nigelcliffe said:

A common issue with programming trailer cars is the lack of any "acknowledgement" signal.

 

To be "read" a DCC chip needs sufficient load on its outputs to generate a pulse back to the programming device.  In a loco, the load is a motor.  A couple of LEDs in a trailer car are insufficient load to generate the pulse.    So, the trailer car often cannot be read. 

With some systems this means "can't be programmed".   With others it can be programmed, but not read. 

 

The pragmatic way out is to put the trailer car decoder in the locomotive-car, program it alone.  Then remove decoder from loco-car, place in trailer car.  Now put loco decoder in loco-car, program that alone.  Once programmed, combine trailer and loco-car and run them on layout.

 

I can't remember what CV29 support is in the Roco Z21 applications.  Years ago, I wrote an explanation and tool to calculate CV29:
http://www.2mm.org.uk/articles/cv29 calculator.htm

 

 

There are many ways of solving issues around two decoders in a multiple unit.

 

- Nigel

The biggest problem I see is that a programing track or piece of is seen by many as loco length (ie 12 inches long), nothing wrong with that but as a mainline loco/Power car would  fill that.

 

Why not use a siding say 4 foot long isolated by plastic rail joiners and have the power feed through a DPDT Centre of switch so you can switch the section from main power and programming power, both decoders then respond and because of the power car the decoder in the dummy is set at the same time. Alright as long as the trailer car is placed on the track the right way in the first place, which if the train/unit is driven onto the programming section/siding it will be.

[Paul80]

I often find it's a simple case of putting both ends coupled together on either main or programming track then write the addresses etc to them both at the same time, that way I find direction issues and lighting issues get sorted automatically, unless its a Dapol then they are always a nightmare that need lots of CV changes just to get the basic directional lighting to work.

[WIMorrison]

The Z21 has a rather nice feature in that a programming track runs as a normal track when you are not in programming mode which means all you need to do is create a length of isolated track fed by the programming output which you drive into, change to the Z21 to programming mode, reprogram, change back to normal mode and then drive back out of - no mucking about with switches or lifting locos on/off track :)

 

As for the length of the programming track, well this can be any length you want - I actually have one that is a continuous oval as i sometimes find it useful to do POM motor tuning on it :)