NCE Powercab and DCC Control Bus Issues.

[devondynosoar118]

I have got all the parts to complete my DCC serial bus, namely RJ12 6p6c plugs, 6 wire flat cable, then crimps. I have NCE powercab running one NCE mini panel in the control panel and two SMD84 decoders to run the Seep solenoids. This all works when connected via TRACK POWER/DCC only. CV 29 in the SMD84 should be set to a value of 24 according to the manual to enable the serial bus to operate the decoder.

 

What I am aiming for is this-

1- Powercab connected to the track and running locos.

 

2- SMD 84's and solenoids powered entirely separately from the track- the decoder is set up to do this, I haven't connected its power input to the same one as the Powercab.

 

3- Using the output from the NCE power panel from the power cab, send the serial bus signal into the layout, chained through the SMD 84's. With CV29 set to the correct value this should enable me to send control signals for solenoids only over the bus.

 

What is happening-

 

1- When the powercab, control panel and SMD 84 is all plugged in to the track supply, everything works.

 

2- When I plug the connector to the serial bus in, the system shuts down like there's a short. It's wired one thumb up, one down, as shown on the NCE instructions. I didn't have the same wire colours as the ones in the manual but assumed this was ok as it's flat cable, so the wires will carry the same signals etc as long as the plugs are wired correctly.

 

3- I am at a loss as to why I am getting power in the serial bus, it was my understanding that it didn't receive power. If it is getting voltage then how can I stop that because it will basically put me back to having the Powercab run the solenoids, which I wish to avoid.

 

Any ideas?

Edited May 14, 2017 by devondynosoar118

[traction]

The serial bus ( the two RJ12 connectors)on the SMD84 is for Loconet.

From SMD 84 instructions:-

 

2.1 Control via LocoNet- Digitrax Users

The SMD84 comes from the factory ready to use by control from DCC commands. To

control the SMD84 via LocoNet, it must be enabled. Connect the SMD84 track power

terminals to the programming track and program CV29 with a value of 48. The SMD84 is

now ready to be controlled via LocoNet. The SMD84 should be connected to track power for proper CDU operation

 

The RJ12 connectors on the Power Panel (PCP) of the Powercab are for linking other panels or connecting other NCE cabs.

You will get power down the cable if using the 6 core wire(6P6C), hence the need to use the correct cable on the left hand port to plug the PowerCab into as it needs power as well.

 

Reading the SMD84 manual again it does look like you can use the RJ12 connectors for the bus. In the table on page 7 it does give the required set up to use with NCE, so setting a CV value of 24, although in the description it does say:-

 

Provides separate bus for bus enabled accessory devices. (This comment is what concerns me as to if it will work correctly)

Allows devices to receive turnout commands from the track (DCC commands) (As per normal use which is what you don't want)

 

you might need to change the wiring in the RJ12 connectors though:-

 

6 WIRE CAB BUS CABLE WITH RJ-12 CONNECTORS
Pin # Color Description
Pin 1 ....... White .............. Power to track
Pin 2 ....... Black ............... Ground
Pin 3 ....... Red ................... - RS-485
Pin 4 ....... Green ............... + RS-485
Pin 5 ....... Yellow ............. +12 volts
Pin 6 ....... Blue ................. Power to track

 

The above was taken from the PowerCab manual, I would chop the plug off one end of the cable you've made up that goes into the PCP panel and reconnect another RJ12 connector but only use Pins 2, 3 & 4 that way no track power or +12volts can be sent down the wires to the other RJ12 connector.

Hopefully you haven't damaged the SMD84 by sending +12v to it, not sure if you would have sent track voltage as well though, need to dig mine out and double check what voltages are actually present on the other RJ12 ports( not the one that the PowerCab plugs into)

 

Any particular reason not to want to run the solenoids from the DCC bus?

The SMD84 has a built in CDU so doesn't take too much current out of the equation.

 

Cheers

 

Ian

Edited May 14, 2017 by traction

[NIK]

I have got all the parts to complete my DCC serial bus, namely RJ12 6p6c plugs, 6 wire flat cable, then crimps. I have NCE powercab running one NCE mini panel in the control panel and two SMD84 decoders to run the Seep solenoids. This all works when connected via TRACK POWER/DCC only. CV 29 in the SMD84 should be set to a value of 24 according to the manual to enable the serial bus to operate the decoder.

 

What I am aiming for is this-

1- Powercab connected to the track and running locos.

 

2- SMD 84's and solenoids powered entirely separately from the track- the decoder is set up to do this, I haven't connected its power input to the same one as the Powercab.

 

3- Using the output from the NCE power panel from the power cab, send the serial bus signal into the layout, chained through the SMD 84's. With CV29 set to the correct value this should enable me to send control signals for solenoids only over the bus.

 

What is happening-

 

1- When the powercab, control panel and SMD 84 is all plugged in to the track supply, everything works.

 

2- When I plug the connector to the serial bus in, the system shuts down like there's a short. It's wired one thumb up, one down, as shown on the NCE instructions. I didn't have the same wire colours as the ones in the manual but assumed this was ok as it's flat cable, so the wires will carry the same signals etc as long as the plugs are wired correctly.

 

3- I am at a loss as to why I am getting power in the serial bus, it was my understanding that it didn't receive power. If it is getting voltage then how can I stop that because it will basically put me back to having the Powercab run the solenoids, which I wish to avoid.

 

Any ideas?

 

Hi,

 

Looking at the manual the SMD84 bus is Loconet compatible but not NCE cab bus compatible. It also has to be powered via DCC.

 

The serial bus incompatibility between manufacturers is common amongst many DCC system parts. Accessory decoders being powered only via DCC is also pretty common.

 

The following might get things working again but in an alternative way:

 

Disconnect serial cable from NCE power panel to SMD84.

 

Reconnect SMD84 to DCC track power.

 

Set CV 29 to option 4 (using SMD84 manual to calculate value for option 4).

 

This should put the SDM84 into DCC gateway mode so that compatible accessories can be connected to the system via serial bus the one SMD84 in gateway mode. The manual doesn't seem to say if the serial bus when option 4 is used is Loconet compatible - it could be a data level version of the DCC track waveform.

 

Regards

 

Nick

Edited May 14, 2017 by NIK

[devondynosoar118]

Right-

 

SMD 84 does support NCE bus, I have set CV 29 on the SMD to a value 24 as suggested in the Team Digital manual and as I stated in my OP, which should allow track signal OR NCE bus.

 

Incompatibility of busses between manufacturers is really stupid, why are we stuck with this when there was reportedly a standard? I chose NCE because it was economical and had the second most common bus communication protocol. Loconet compatible was too much extra ££.

 

I also already stated that the SMD 84 is working correctly on DCC only, from the Powercab, with no serial bus connection at all, meaning that CV 29 must be correctly set for that option.

 

SMD 84 is fine, it works the minute you go back to track power/DCC feed.

 

I did try a 4 pin connection, but as I have flat cable changing the wires around is awkward. I will get some pictures.

 

Thanks for responses so far, I will see if I can get more detail for you to work on.

 

Edit- Pictures incoming, first the wire and connectors I have on hand. If the wire is no good a working link to some correct cable would be fine, or a colour/pin suggestion with what I have, as only I will be messing with it.

Edited May 14, 2017 by devondynosoar118

[traction]

Right-

 

SMD 84 does support NCE bus, I have set CV 29 on the SMD to a value 24 as suggested in the Team Digital manual and as I stated in my OP, which should allow track signal OR NCE bus.

 

Incompatibility of busses between manufacturers is really stupid, why are we stuck with this when there was reportedly a standard? I chose NCE because it was economical and had the second most common bus communication protocol. Loconet compatible was too much extra ££.

 

I also already stated that the SMD 84 is working correctly on DCC only, from the Powercab, with no serial bus connection at all, meaning that CV 29 must be correctly set for that option.

 

SMD 84 is fine, it works the minute you go back to track power/DCC feed.

 

I did try a 4 pin connection, but as I have flat cable changing the wires around is awkward. I will get some pictures.

 

Thanks for responses so far, I will see if I can get more detail for you to work on.

 

 

I understand what you've done BUT, 4 core wire will still be connecting ground to ground and +12v into the ground connection on the RJ12 connector of the SMD84, hence why I said use only 3 wire connection so no chance of any unwanted voltages, just make sure it is ground to ground and then are the data signals the correct way round.

 

At least it still all works when you go back to standard DCC control, so no damage to the functionality of the board!

 

Cheers

 

Ian

Edited May 14, 2017 by traction

[devondynosoar118]

Noted- I am adding to my post so you can see what I have colour wise. I will definitely try using less wires in the second plug.

 

Bearing in mind I am working in N gauge and don't need more than 2 locos running at any time on this layout would the Powercab be able to run this lot provided I don't add any more load? There are 5 more points connected to a second SMD84 on the other station board.

Edited May 14, 2017 by devondynosoar118

[traction]

My PowerCab has run a couple of SMD82's (just using the DCC track bus for power) both having all outputs connected and still running 2 N-gauge locos. so it should be OK.

Turn on the ammeter in the Powercab and see what current is being drawn.

I connected all 8 points up then set a macro to fire all 8 while I watched the current draw on the Powercab, it wasn't too much but each point is fired after a second delay while the capacitors recharge for the CDU.

I found it to be the most reliable accessory decoder I've used and the ability to have switches as well as DCC control the points made it ideal.

 

I've just checked and there is 13.4v DC coming out of the PCP RJ12 connector on pins 2 and 5.

 

You could as a test, cut the RJ12 lead in half and connect the wires into a choc block terminal strip so one side with the RJ12 connector would plug into the SMD84 the other into the RJ12 port on the PCP panel.

That way you can just isolate individual wires and see what works, would be a good test.

 

Cheers

 

Ian

[devondynosoar118]

That is a good idea about the choc block.

I may just leave it on DCC for now then, if it's low current draw. I can still use the PCP port bus for cab extensions to the fiddle yard if required.

How about the wire I have, any use or do I need to work with something else? If so where to buy it in 10m or so roll?

[traction]

I think that wire should be fine, Digitrains made some up for me and it's just standard flat cable, but grey instead of white.

To me it looks like the only reason it's failing is the +12v on pin 5 from the NCE PCP panel going straight into the ground on the SMD84 RJ12 socket.

Once the 12v is removed it shouldn't short out, if it works and sends signals is a completely different issue though!

 

Cheers

 

Ian

Edited May 14, 2017 by traction

[devondynosoar118]

Right, that I can fix. What connector should I use on the SMD84 end? I get one end with RJ 12 6p6c for the PCP, then find ground and RS485 pair, which I will need to find by mapping my 6 cable colours vs the 6 shown in the NCE manual.

If I can get it to work it will be an achievement by the sound of it. It should work in theory.

Here's the set up working on DCC, if there's any improvements you can see then suggestions welcome.

[traction]

You can just use the RJ12 6P6C connector each end.

 

Just don't connect up pins 1,5 & 6 as pins 1 & 6 are track power(although I didn't measure any voltage from the PCP on these two pins best to leave them off) Pin 5 is the +12v output so we don't want this either.

Connecting the rest should give you the two data cables on pins 3 & 4 with a ground on pin 2.

I have no idea which way the data cables should be connected I'm assuming it will be as per the diagram so Pin 3 is -RS-485 and pin 4 is +RS-485 if you have no short circuit but the points don't operate then you could try swapping these two round, but try it as is and see what happens.

 

Cheers

 

Ian

[NIK]

 

Right-

SMD 84 does support NCE bus, I have set CV 29 on the SMD to a value 24 as suggested in the Team Digital manual and as I stated in my OP, which should allow track signal OR NCE bus.

Incompatibility of busses between manufacturers is really stupid, why are we stuck with this when there was reportedly a standard? I chose NCE because it was economical and had the second most common bus communication protocol. Loconet compatible was too much extra ££.

I also already stated that the SMD 84 is working correctly on DCC only, from the Powercab, with no serial bus connection at all, meaning that CV 29 must be correctly set for that option.

SMD 84 is fine, it works the minute you go back to track power/DCC feed.

I did try a 4 pin connection, but as I have flat cable changing the wires around is awkward. I will get some pictures.

Thanks for responses so far, I will see if I can get more detail for you to work on.

Edit- Pictures incoming, first the wire and connectors I have on hand. If the wire is no good a working link to some correct cable would be fine, or a colour/pin suggestion with what I have, as only I will be messing with it.
IMG_2054.JPG

 

Hi,

 

I can see from the manual the SMD84 is powered from the DCC track power and can be controlled from NCE by setting CV29:

 

 

 

Allows devices to receive turnout commands from the track (DCC commands).

Also manual says it is a separate serial bus and gateway mode works with NCE and others - so the chances it would be NCE cab bus compatible are slim.

 

Only the DCC bus is standardised. On DCC system components the manufacturer is free to design other interconnections such as cab busses as they please.

 

If its any consolation I once bought a Digitrax signal controller and found that although it could be setup/programmed via DCC I couldn't change the state of the signals with DCC.

 

 

Regards

 

Nick

 

 

 

 

[devondynosoar118]

Thanks again both of you- I have below a page from the manual showing the 4 wire cab bus with the pins numbered. My cable on the left, which has the "wrong" colours. I will sit down later and try and work out what goes where to make up the lead suggested to test again.

 

 

Worst case scenario I have it all working on the track feed. Cables would be much tidier the other way, but we will deal with that later.

Edited May 14, 2017 by devondynosoar118

[NIK]

Thanks again both of you- I have below a page from the manual showing the 4 wire cab bus with the pins numbered. My cable on the left, which has the "wrong" colours. I will sit down later and try and work out what goes where to make up the lead suggested to test again.

 

IMG_2056.JPG

 

Worst case scenario I have it all working on the track feed. Cables would be much tidier the other way, but we will deal with that later.

 

 

Thanks again both of you- I have below a page from the manual showing the 4 wire cab bus with the pins numbered. My cable on the left, which has the "wrong" colours. I will sit down later and try and work out what goes where to make up the lead suggested to test again.

 

IMG_2056.JPG

 

Worst case scenario I have it all working on the track feed. Cables would be much tidier the other way, but we will deal with that later.

 

Yes,

 

That's the NCE cab bus - I understand its for carrying data to/from the command station and additional NCE cab throttles, NCE USB interface, NCE auxilary input units (AIUs) and NCE Panels (depending on the system).

 

 

It's not Loconet compatible data wise so I interpret the SMD84 manual as allowing the option of NCE control via the DCC track bus only (no connection to the serial bus from the NCE cab bus should be attempted).

 

From DCC wiki:

 

 

Are you not worried about damaging the RS-485 devices in the NCE PowerCab?.

 

Regards

 

Nick

[devondynosoar118]

They survived the last attempt and I have a spare eprom. Going to try running it off DCC for now. The SMD 84 instructions seemsped to me to say it is NCE compatible via the bus otherwise why turn the bus on through CV29? Surely it would just say to use gateway mode and ignore the bus?

It's certainly as clear as mud, which is what I have come to expect from the majority of DCC manufacturers literature.

Edited May 14, 2017 by devondynosoar118

[Nigelcliffe]

Two suggestions to throw light on this issue:

 

1 - try some US forums where the products in question might be in more widespread use.  Such as the NCE forum on Yahoo!

 

2 - email TeamDigital and ask how they recommend connecting things for the proposed setup.  They may reply, some US makers are pretty good at supporting users.  I've no experience of asking TeamDigital.

 

 

 

- Nigel

[devondynosoar118]

Thank you Nigel. I had a skim through some US sources before coming on here to ask. I obviously need to improve my search discipline!

I have email Team Digital and will post their reply for posterity.

 

Edit- Received a very prompt reply from Team Digital-

They say the SMD84 is NOT compatible with the NCE bus, they also recommended a booster module that they sell to keep the signal to the accessories going in the event of a short. This is the board they sell for that- http://www.teamdigital1.com/prod_catalogue/dccboost_product/dccboost.html

Edited May 15, 2017 by devondynosoar118