Lenz RS feedback bus

[Edwin_m]

DCC diehards of this forum may remember my previous tribulations getting reliable detection with the Littfinski RS-8 detectors on the Lenz feedback bus. I have LZV100 and LH100 both at software version 3.6.

 

I have now moreorless got the layout up and running again after a long period out of use due to building work. The upside was that I used this time to do some long-postponed and much dreaded wiring jobs including replacing the complete RS bus round the layout with twisted pair cable.

 

The result appears to be a considerable improvement, though probably too early to say things are perfect! Several people on the previous thread reported their RS buses working fine despite not being twisted, but I'd suggest this is one of those issues (like not looping the main DCC bus) where you can probably get away with it most of the time but occasionally you can come unstuck. In my case the bus was in a ribbon cable with various other buses, and despite none of them carrying track or point currents I guess the high degree of coupling was corrupting the feedback signal.

 

A few hints and tips on the RS-8 and the RS bus in general:

 

(1) The RS-8s only send a message on power up, when one of their inputs changes and I think immediately after their address has been set up. In each case they seem to update the command station with the state of all inputs. There is no regular update to the command station to say the module is still there and as far as I can tell no way the command station can force the module to transmit. Consequently a loss of one message can cause a problem that persists for a while. In my case several tracks on one module would show occupied with no train present but would usually sort themselves out when the first train went through.

 

(2) As a consequence of (1) above, the fact that the handset displays feedback from a module does not confirm that that module is still on line, merely that at least one message has been received from it since the command station powered up. The best way of proving a RS-8 is currently working is to tickle one of its outputs with a resistor and watch the feedback bit numbers on the handset.

 

(3) As well as flashing steadily during address setup, the LED on the RS-8 flickers whenever it transmits on the RS bus. I think it only transmits when the RS bus is connected properly and one (perhaps both) of the track feeds into the module has DCC track signal.

 

(4) A quick way of checking the continuity of the RS bus is to short circuit it. This will trip out the command station in the same way as a track short, but if you try to reset the short while it is still there, "OD" will flash on the display.

 

(5) I think the RS bus has to be connected with the correct polarity (R=R and S=S on all modules).

 

(6) RS-8s seem to lose their addresses when powered down for a couple of months.

[Mike Friedman]

DCC diehards of this forum may remember my previous tribulations getting reliable detection with the Littfinski RS-8 detectors on the Lenz feedback bus. I have LZV100 and LH100 both at software version 3.6.

 

I have now moreorless got the layout up and running again after a long period out of use due to building work. The upside was that I used this time to do some long-postponed and much dreaded wiring jobs including replacing the complete RS bus round the layout with twisted pair cable.

 

The result appears to be a considerable improvement, though probably too early to say things are perfect! Several people on the previous thread reported their RS buses working fine despite not being twisted, but I'd suggest this is one of those issues (like not looping the main DCC bus) where you can probably get away with it most of the time but occasionally you can come unstuck. In my case the bus was in a ribbon cable with various other buses, and despite none of them carrying track or point currents I guess the high degree of coupling was corrupting the feedback signal.

 

A few hints and tips on the RS-8 and the RS bus in general:

 

(1) The RS-8s only send a message on power up, when one of their inputs changes and I think immediately after their address has been set up. In each case they seem to update the command station with the state of all inputs. There is no regular update to the command station to say the module is still there and as far as I can tell no way the command station can force the module to transmit. Consequently a loss of one message can cause a problem that persists for a while. In my case several tracks on one module would show occupied with no train present but would usually sort themselves out when the first train went through.

 

(2) As a consequence of (1) above, the fact that the handset displays feedback from a module does not confirm that that module is still on line, merely that at least one message has been received from it since the command station powered up. The best way of proving a RS-8 is currently working is to tickle one of its outputs with a resistor and watch the feedback bit numbers on the handset.

 

(3) As well as flashing steadily during address setup, the LED on the RS-8 flickers whenever it transmits on the RS bus. I think it only transmits when the RS bus is connected properly and one (perhaps both) of the track feeds into the module has DCC track signal.

 

(4) A quick way of checking the continuity of the RS bus is to short circuit it. This will trip out the command station in the same way as a track short, but if you try to reset the short while it is still there, "OD" will flash on the display.

 

(5) I think the RS bus has to be connected with the correct polarity (R=R and S=S on all modules).

 

(6) RS-8s seem to lose their addresses when powered down for a couple of months.

 

I have around 90 blocks detected by 12 RS-8s, the units are spread over the 3 sections of the layout each 28ft. x 4ft., the local feed-back is twisted cable (twisted manually in a drill chuck), usually around 4ft. long from each RS8, these local runs then join the main feed-back bus that is shielded microphone cable (this is not twisted) as I happened to have a spare drum of the stuff, the main feed-back bus runs under each section of the layout.

 

The main feed-back bus attaches to the Lenz LZV100, and a Lenz serial connection goes from the Xpress net bus to a laptop, where RR&co interprets the info for it’s display.

 

The above has been in operation for over four years and none of the 12 RS8s have ever lost their address (although the longest it has gone without powering up is about three weeks).

 

All static decoders and the RS8s are fed from a second control/power district powered by a Lenz LV101 and dedicated Lenz TR100 transformer. Power to all accessories is from a separate power bus from a second dedicated Lenz TR100 transformer.

 

The only problem I have sometimes encountered is occasionally if the LZV 100 shuts down due to a short, when it powers back up, all the blocks show a random occupied or not occupied status on the RR&co screen; the solution is to power down the transformer that feeds the RS8s and on power up the correct occupancy is once again shown for all blocks.

[perjan]

Besides the problem of electrical noise picked upp by the RS-bus "flicker" from  bad wheel / track connections occurs.

 

I am using the LDT-RS-16 feedback unit for detection of occupied tracks with a Lenz LZV100 central. The feedbacks are presented to TrainController .
Any "flicker" on this feedback can be reduced by the filter function "memory" in TC giving clean indications of occupied tracks.

 

But all "flickers" from bad wheel / track connections are still there on the RS-bus.
Having lots of trains in operation reporting their occupations of lots of track sektions
the traffic on the RS-bus must be quite busy with lots of false indications from these "flickers". Lots of unwanted messages.

I know that Lenz feedback units and others have inbuilt filters to avoide such "flicker" to make a more clean communication on the RS-bus.

Does anyone know if Littfinski LDT-RS-16 have such filter?

 

[RFS]

Using RS8s for feedback I had quite a few problems with RR&Co not seeing the status updates, and hence not recognizing a train had entered a block. Eventually I concluded the problem was not the RS8s or the Lenz feedback bus, but the Lenz LI-USB PC interface. Lenz could find no problem with it, but replaced it nonetheless.  As the replacement had the same problem, I went back to them and they immediately offered me the serial interface LI101F which they sent me free of charge. I assumed Lenz were aware of problems in certain situations with the LI-USB but they never alluded to that in our communications.

 

As my PC had a serial interface on the motherboard, I accepted their offer. When it arrived, I plugged it in, started RR&Co and never looked back. Sometimes I could only run 5-10 minutes before a failure occurred but with the serial interface I never had a problem. Subsequently on the German forum of the RR&Co website I found a thread where several others were reporting the same problem.

 

I've since upgraded to the 23151 LAN/USB interface, and connect directly to the PC via the LAN port thereby avoiding all USB converters. No problems at all.

 

Incidentally I see that the new LZV200, when it ever arrives, will have the PC interface built in.