DCC issue with Heljan Turntable

Hi,

I have a layout which runs under Railroad and Co. It has a Heljan TT which is setup to run under DCC. The main DCC Controller is a Lenz LZV100. The TT is attached to the seperate points bus. The TT works fine under the Lenz DCC and RR&C, BUT does random movements, ie every couple of minutes it will just take off to a new track. This puts it out of sync with the RR&C as it will now be on track 8 whereas RR&C thinks its on track 1.

Heljan tech support believes it is interference on the DCC bus.

So I have tried a number of things:

1. Made sure there is no duplicate numbers there are 80 points and 25 signals all DCC.
2. Ran a sniffer to see if any calls were being made to the TT DCC addresses - NONE.
3. Covered the cable from TT Controller to TT with Aluminium foil.
4. Changed the range of the TT DCC addresses, it happens less with a higher address, however the heljan TT is limited to addresses below 250.
5. Tried a different DCC controller on the TT. A SPROG 3, PI-SPROG and Digikeijs, but these will not driver the TT. More on this below.
6. Ran a seperate DCC BUS just for the TT. Seemed to reduce incidents but not eliminate them.
7. Setup a test with JMRI so that not using RR&C and did have the issue. So its not the RR&C.

So the SPROG, PI-SPROG and Digikeijs will not operate the Heljan TT. I have put a sniffer on and the commands issued by the LENZ, SPROG, PI-SPROG and Digikeijs and they all look the same. But the TT will not respond to the commands. Also the SPROG nd PI-SPROG will not issue any commands if there is no other load on the DCC. So I need to connect them to a track with a loco for them to issue a DCC command.

I went to SPROG and Heljan Technical support and each blamed the other. Only tried the Digikeijs in the last couple of days.

So does anyone have any ideas on what may be happening. If I could get the SPROG to drive the TT I would set it up as a seperate BUS.

Thanks
Brian

 

I tried one early in my testing and it didn't seem to make any difference. I just added one again and retested. No change in the results.

 

Thanks for the response, Yes only TT via a length of non twisted cable that isn't under the layout running across the room on the floor. It could only be controlled by the Lenz or RR&co via the Lenz.

 

I tried something else today.

Moved all the points onto the SPROG 3 and The TT was the only accessory on the LENZ. The cable from the LENZ to the TT was across the floor and no where near any other buses.

Disaster, the SPROG uses the opposite polarity to the LENZ so had to change all the points to operate the other way. The SPROG will not communicate with some of the points. And some points only operate after a couple of prompts. Means you can't use RR&co to control trains as too unreliable.

Also the TT still did a random turn.

Cheers

Brian

 

Jim,

Yes the TT can be run on DC, You supply 16V AC instead of DCC power to the TT. I have run the TT in this configuration when I have has Train Club around. However this defeats the whole purpose of being able to use the TT with RR&Co. I like to sit at my desk and move trains in and out of the engine shed.

The turntable was installed about two years ago and when first installed didn't have the problem. The issues started about 18 months ago. and steadily got worse. The issues started when I started to install dapol signals. However I have isolated all the signals at this time.

I sourced a new control box and PCB (which fits inside the TT) but that did not fix the problem.

Scratching head.

Brian

 

Yes it doesn't have the issue when running on 16VAC.

 

Jim, The control box has 4 inputs: A,B to feed power to the tracks and C,D for power input to the control unit. CD can accept either DCC or a specified 16VAC. It automatically changes when it has 16VAC. We have a second Heljan TT at our club and we run it on 13VAC. So I think it uses the same circuit but with no DCC signal being available for interpretation. The TT logic for what tracks and driving the TT is all on the PCB in the bridge. The control box has limited functionality.

Cheers
Brian

 

Yes a specific DCC accessory code relates to a track, so you send codes related to the tracks you want. In my case there is a base address 60, which relates to DCC accessory codes 237 to 246 (I have 10 tracks). Even using the manual commands you specify the track you want. There is no next track function.

There are four inputs to the control box = Track Power and DCC/16VAC for the control unit. From the control unit to the Bridge there is an RJ45 cable meeting up with 8 wipers. There was a MERG article in Dec 2018 which gave great info on the TT. The wipes are 4 for Track power (double redundancy), 2 for 12V DC and Ground, A comms wire Rx/TX and a 12V supply to the IR led.

Yes I regularly clean the wipes and bottom of the bridge with IPA.

Yes Motor, Control PCB and sensor are within the bridge.

When it moves unannounced to will go to a track and align with that track. So it might be on Track 1 but then go to track 8. a minute later it goes to track 5. etc. Meanwhile RR&Co still thinks its on track 1. So it sends a loco thinking the bridge is at 1 and it ends up in the pit.

I have a schedule which runs about 10 trains over a 20 minute period and during that time the TT will move between 1 and 5-6 times. Its seems totally random. That may well be because RR&CO moves things in what is a seemingly random timing depending on relative locations of trains.

I have been unable to isolate a command that starts the unannounced moves.

Cheers

Brian

 

1) Yes the TT control panel always shows the correct position
2) No once an unannounced move happens the RR&Co shows where it was not where it is now.

So RR&CO moving a train onto the TT to then move to a new track and off. Ie Loco entering the shed.

RR&CO:
1. checks the track is vacant
2. books the blocks, Including the TT block.
3. Sets any points
4. Turns the TT to right track for an incoming loco. In my case track 1. If it is already on track 1 NO command is given.
5. Moves the loco through onto the TT. There are sensors that detect the loco on the TT and to sense where to stop.
6. The loco stops on the TT will be moved to the exit track. say track 8. If the setting say to eit in reverse then the TT will turn the loco round.
7. The RR&Co will tell the TT to move to the exit track. Say track 8. If the setting say to exit in reverse then the TT will turn the loco round.
8. TT stops on the exit track.
9. Loco then told to move off the TT.

So as you can see from above RR&CO does already issue a command before the Loco arrives. Just doesn't do it if it is already on the required track.

The Heljan TT will do a 180deg turn if you send it the same number it is already on. So in my case if it is on 1 and it is send 1 it will do a 180 turn and end up on track 7. Meanwhile RR&Co will think it is one, and send the loco while the TT is actually doing a 180 turn = loco in pit.

I have been thinking of adding a switch so I can switch the TT from DCC to 16VAC. If being used manually I can have it on 16VAC. If i want to do some computer control I can put it on DCC. Maybe have the switch a DCC activated relay from an Arduino.

The unannounced turns really only occur when there is lots happening. Ie several trains running and lots of points being changed.

Cheers
Brian

 

Jim,

Yes while in DCC mode, you can operate the turntable manually or via a DCC accessory command.

One momentary movement could not cause the TT to move.

To manually move the TT, you have to:

Press the Go/Set Button
Press the Up or Down arrows to get the required track number
Press the Go/Set Button

The unannounced moves are very rarely one track. Often it goes 1 - 8 - 5 -7 or variations like that.

Also I have two control panels and both have the same issues.

Still scratching.

I have reverted everything back to normal after trying the various DCC command stations. It is really annoying that the SPROG 3, Pi-SPROG and DigiKeijs will not operate the TT.

The only thing I haven't done recently is change the PCB in the bridge. May do that today.

Cheers
Brian