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Offline applor  
#1 Posted : 24 March 2019 02:09:25(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,424
Location: Brisbane, Queensland
Gents,

A couple of my S88 sensors in completely different areas/modules have unfortunately developed the most frustrating bug of rapidly flickering when I turn track power on.

I can rule out S88 module/bus problems, since the fault occur no matter which input/module I connect the track to.

What is interesting is how it only occurs when I apply power (my S88 bus is through PC S88 and not the CS2, so I can see sensor events with the CS2 off)
My previous S88 issues have been constant regardless of power and rather simple to identify as joins between sections (using piko plastic rail joiners).

In this case I have cleaned between the rails of the trouble sensor with no improvement and also the flickering only occurs with power applied.

Currently a bit baffled as to the cause. I know its mechanical but not sure how, since the rail join is open and it only occurs with power applied.

Could a high resistance bridge between power and the rail cause this?

My only though so far is to rule out the rail separation as the cause by cutting it clean open with a dremel.

Edited by user 21 April 2019 07:03:01(UTC)  | Reason: Not specified

modelling 1954 Germany (era IIIa)
Offline applor  
#2 Posted : 24 March 2019 23:49:13(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,424
Location: Brisbane, Queensland
The join in question, looks clean. The other join can't be at fault since it connects to another sensor section so that sensor would be triggering if that was the case.

IMG_4274.JPG

No replies so I will assume no one has any better ideas - I will cut the above join tonight and see if the problem is fixed.
modelling 1954 Germany (era IIIa)
Offline JohnjeanB  
#3 Posted : 25 March 2019 00:20:46(UTC)
JohnjeanB

France   
Joined: 04/02/2011(UTC)
Posts: 649
Location: Paris, France
Hi Applor

I don't know exactly what "S88" you use to collect information to the PC.
My system includes mostly various Märklin S88: 6088, 60881, 60882, 60883, DigitalBahn DS2010.
Until recently the bus was dealing with 0V+5V levels but under a very high impedence (10 to 100 kOhm) associated with clamping diodes to make sure the converted signal is within the CMOS circuit voltage range (the circuit that is passing the signal to the CSx or to the PC) and a resistor in series to limit the current to very low levels.

Sorry for the explanation. It means that long wires are subject to mutual induction coming from other wires (especially the power digital cables).
Also -of course- your PC-based S88 must share the voltage of your layout or use entries with opto couplers.

First step: disconnect the faulty entries at the S88 entry. If the signal stops changing it means you need to re-arrange the wiring which bringes the sensors to the tracks.
If it does continue changing you have a problem with the sensor systems (e.g.: with the old 6088, the cable may be too long or have problematic connectors.

I recently discovered that my Wifi router (connecting my PC to my CS2) was creating problems (causing erroneous train detections) All went back to normal when I switched it off.
Now I need to install the WiFi antenna not so close to the Layout. In the meantime I use a crossover Ethernet cable.

Cheers

Jean
My lay-out videos
latest vid
humping yard
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Offline DaleSchultz  
#4 Posted : 25 March 2019 00:31:59(UTC)
DaleSchultz


Joined: 10/02/2006(UTC)
Posts: 3,253
my thought is also some sort of electromagnetic interference but I don't know what could be doing it. Did you recently add some more wires for unrelated stuff?
Try disconnecting other things nearby the s88 lines. I doubt it is a mechanical connection on the tracks itself.
Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline applor  
#5 Posted : 25 March 2019 03:14:11(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,424
Location: Brisbane, Queensland
Gents,

Thanks for the replies. I have Tams S88-3 modules connected to the LDT HSI-S88 over USB to my PC. The HSI-S88 allows 3 separate S88 bus links, which I have configured with 4 modules per bus.

This particular sensor is located on the 2nd module in the bus and as mentioned the fault moves with the track (If I swap the wires with a different S88 port, the flicking sensors follows the wire)
I have made no additional cabling changes recently either.

I will do some more testing and messing about when I get some time but so far the only constant is the track section so it stands to reason its the cause somehow.
modelling 1954 Germany (era IIIa)
Offline DaleSchultz  
#6 Posted : 25 March 2019 04:18:43(UTC)
DaleSchultz


Joined: 10/02/2006(UTC)
Posts: 3,253
Originally Posted by: applor Go to Quoted Post
the only constant is the track section.


and the wire running to it? or did you switch wires at the track end?

Dale
Intellibox + own software, K-Track
My current layout: https://cabin-layout.mixmox.com
Arrival and Departure signs: https://remotesign.mixmox.com
Offline applor  
#7 Posted : 25 March 2019 11:32:26(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,424
Location: Brisbane, Queensland
Originally Posted by: DaleSchultz Go to Quoted Post
Originally Posted by: applor Go to Quoted Post
the only constant is the track section.


and the wire running to it? or did you switch wires at the track end?



The wire is about 20cm long and nowhere near anything else so it is definitely not the cause.

I have recently added some new isolated track sections and had to run a wire 5m long and in proximity to other cables and they exhibit zero false triggers.

edit: I was going to try and fault find this for 30 minutes tonight, except I've powered everything up and now it's not doing it Blink ConfusedCursing
modelling 1954 Germany (era IIIa)
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Offline JohnjeanB  
#8 Posted : 25 March 2019 12:05:16(UTC)
JohnjeanB

France   
Joined: 04/02/2011(UTC)
Posts: 649
Location: Paris, France
Hi

When dealing with this kind of problems I found the following:
- initially when painting the rail's side or ballasting with glue I have found false detections which disappear after a few hours drying
- some short section with "Dremel cuts" may slide and make contact

But in the long run, it is the cabling arrangement that is key (so changing the receiving TAMs entry will not change the problem.
Try instead to have a separate loose wire connecting the two points of the faulty of course having disconnected the initial wiring.

On some circumstances on some entries I have:
- reduced the sensivity of the S88 entry with a pull-up resistor (5 to 10 kOhms) between a +5 VDC and the entry
- reduced electrical noise with a capacitor between the entry (+) and the ground (0). In my case the noise source was a decoupler.
Cheers

Jean
My lay-out videos
latest vid
humping yard
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Offline applor  
#9 Posted : 30 March 2019 06:56:56(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,424
Location: Brisbane, Queensland
I went to drive the trains today and the sensor fault was there and didn't change through several restarts.

If I move sensor position, the fault follows - this rules out interference on the module bus, otherwise the same position would be trigger.

As mentioned, the cable from track to S88 module is about 20cm and nothing else nearby - this rules out interference on the sensor wire.

I test resistance between sensor section and the track earth and its open circuit - so it is not an earth short on the isolated track section.

I thought the problem may be related to power supply for the HSI-S88 USB but I tried every PSU I have and the sensor problem stayed.

I'm going to have to try some of Jeans modifications.

Otherwise I feel I've hit a brick wall which now prevents me from running my trains!

modelling 1954 Germany (era IIIa)
Offline applor  
#10 Posted : 30 March 2019 12:12:20(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,424
Location: Brisbane, Queensland
I have since had some time to think and determined I can run the following tests to help pinpoint a possible cause:

1) Test the HSI-S88 using their dicostation software to confirm the sensor events are not somehow phantoms in Rocrail

2) Use alligator clips and wiring to connect the isolated rail, to better rule out any issues with the wire or solder joint

3) Test for voltage between the isolated rail and the active and neutral of the track system. Possible low resistance to the active track connection.
modelling 1954 Germany (era IIIa)
Offline PMPeter  
#11 Posted : 30 March 2019 18:11:19(UTC)
PMPeter

Canada   
Joined: 04/04/2013(UTC)
Posts: 1,020
Location: Port Moody, BC
I had the same problem with one of my home made contact tracks. I rebuilt and resoldered it 3 times to make sure I had no leakage. I finally cut the isolated section all the way through on both ends to make sure I was not getting any form of leakage from the "B" side below the K track and separated the gaps with styrene, all to no avail. I swapped out the standard LDT S88 module with an LDT opto isolated version and the problem went away and has not returned in over a year.

From a pure electrical logic point of view it just made no sense.

Peter
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Offline applor  
#12 Posted : 31 March 2019 06:12:43(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,424
Location: Brisbane, Queensland
Originally Posted by: applor Go to Quoted Post
I have since had some time to think and determined I can run the following tests to help pinpoint a possible cause:

1) Test the HSI-S88 using their dicostation software to confirm the sensor events are not somehow phantoms in Rocrail

2) Use alligator clips and wiring to connect the isolated rail, to better rule out any issues with the wire or solder joint

3) Test for voltage between the isolated rail and the active and neutral of the track system. Possible low resistance to the active track connection.



Well I performed the above tests today, results were:

1) Unfortunately dicostation does not poll events, it can only check for the HSI and do firmware, so this test was not possible
2) No change, sensor still flickered
3) standard 17V AC, same as every other sensor. In fact I performed all manner of resistance and voltage tests and the trouble section was exactly the same as those others that work OK.

Originally Posted by: PMPeter Go to Quoted Post
I had the same problem with one of my home made contact tracks. I rebuilt and resoldered it 3 times to make sure I had no leakage. I finally cut the isolated section all the way through on both ends to make sure I was not getting any form of leakage from the "B" side below the K track and separated the gaps with styrene, all to no avail. I swapped out the standard LDT S88 module with an LDT opto isolated version and the problem went away and has not returned in over a year.

From a pure electrical logic point of view it just made no sense.

Peter


Thanks for your reply, you certainly saved me from going through the same process. As a result I then performed a new test that Fabrice lead me to via PM:

French_Fabrice wrote:
HI Eric,

IN the past, when I had constant flickering, it was related to a missing (common) ground wire connected to the S88 bus...

I know you know that, but it's the only thing I'm thinking about... Possibly a ground wire close to your section which has trouble ?
Flickering means Voltage reference (i.e. ground) is not stable or missing... Or an opto-coupler which is defective in some electronics ?

Good luck
Fabrice



So with my setup there was certainly no missing ground wire. I first tried removing the ground wire to the module with flickering sensor (R2). This made no change to anything at all.

I then thought, do I need every S88 module individually connected to earth if there was no change to working sensors or the flickering sensor?

So I then proceeded to remove the S88 module earth connection for all the modules in that bus (S88 modules R1 to R4)

After doing that, all the working S88 sensors were still OK but to my astonishment the flickering sensor was triggering about half the speed it was before! Blink

Certainly onto something here!

I then went through all the remaining S88 mobules and removed the earth reference connection (another 8 modules).

I then checked Rocrail and hey presto, the flickering on both the trouble sensors was now gone! BigGrin

Therefore the only earth connection is the one directly to the HSI S88 power input terminals (as per documentation).

My best guess is that there was some sort of earth current loop happening as a result of each module being earthed.

It is completely baffling how only 2 random sensors on completely different S88 modules and S88 bus happened to be affected and none of the others.


I just want to close off by saying a big thanks to everyone who replied and especially Fabrice who happened to lead me to the solution.

Hopefully this thread will be of use to others who may end up with the same problem.
modelling 1954 Germany (era IIIa)
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Offline applor  
#13 Posted : 06 April 2019 06:11:02(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,424
Location: Brisbane, Queensland
Can you believe I started up my trains today and one of the two sensors decided it wanted to flicker with power on again?

It only flickers once a second (previously 50 times/second) and the other sensor isn't flickering at all.

I definitely had a solution here but it seems that it is not quite enough to completely resolve the problem.

There is only the main sensor earth left, so there is nothing else I can really do I think.

Thankfully the sensor playing up is in a pass through block so I have just left it disconnected.

I think the only way to resolve this one is to replace the S88 module with an opto-isolated version.
modelling 1954 Germany (era IIIa)
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Offline blid  
#14 Posted : 06 April 2019 12:27:41(UTC)
blid

Sweden   
Joined: 02/01/2012(UTC)
Posts: 135
Location: Stockholm, Sweden
I once had a similar problem. On the left bus I had a mix of LDT-RM-DEC-88-Opto, Marklin 60880 followed by two LDT RM-88-N-Opto. I had that mix on the previous layout with no problems. The only way to get rid of the flickering was to replace one of the RM-88-N-Opto for a RM-DEC-88-Opto from another leg and move the last RM-88-N-Opto to the middle leg.
I should have worked as it was, but it didn't.
All my units have the reference connected (some are for turnout position hence reference is power). All 23 LDTs are Opto and have the suggested diod and the reference reversed.
CS2, 60215, 4x60174, C-tracks, LDT HSI-88, TC Gold. OneGauge Marklin and MTH, CS1 Reloaded on LGB tracks. MTH 3-rail 0-gauge, DCS on GarGraves tracks.
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Offline applor  
#15 Posted : 11 February 2020 03:00:42(UTC)
applor

Australia   
Joined: 21/05/2004(UTC)
Posts: 1,424
Location: Brisbane, Queensland
I am posting on this old thread again as I have further knowledge to share in the hope others avoid these problems.

Things had been mostly trouble free except for one section that would intermittently decide to flicker, including one new section where I had added a sensor by cutting the rail.

I found that where I cut the rail was causing a flickering sensor because there was a tiny flap of metal below the rail where the cut had been made.
It wasn't too hard to identify and remove the small metal shard which resolved the problem completely.
It made me think that these problems must always be caused by a high resistance contact between S88 section/rail and the power rail underneath the track.
They flicker because of the AC current which only returns occupancy for one half and they are intermittent due to the high resistance - which is too high to cause a short but can cause detection because S88 is so sensitive.

I had a track section which had been playing up very rarely over the last few months and was unable to completely resolve it, because I had been working on the end rail connection thinking the problem was there (which wasn't the cause) but the movement of the track when working was enough to sometimes 'fix' the S88 detection for a period of time.
After my realisation with the new sensor and the cut track I decided to pull this whole track piece out (not easy) and inspect it. Cleaned the solder joins and what not.
I then found a chunk of something, perhaps rail plastic, that was stuck in the gap between the rail and the power rail below. Removing it resolved the problem.

As it happens I then had two other sections last weekend also flickering again. One piece of track I removed but could not find a clear cause for flicking. I removed the rail from the track (2205 flex) and cleaned everything. Fixed.

Last flicking sensor was a very short section as it was a single curve track piece (2231). This one I could not resolve with cleaning and unlike 2205 flex tracks, you can't easily remove the rail from a 2231.
I didn't give up though and decided to cut the power rail underneath the rail where the solder join to the S88 rail was located as it seemed the most likely location of the problem.
Since the power rail runs both sides of the track, you can actually cut one side off and it will still feed the centre studs.
As it happens I found more of this plastic/rust gunk below my solder join:

IMG_6725.jpg

However unlike the previous track piece, cleaning that stuff out from below the rail did not resolve the problem! The power rail had been cut regardless, so it couldn't be the cause anymore (or not the only cause).

With no other option left, I decided to remove one side of the power rail from the entire piece of 2231 track - that is the piece below the S88 rail but also leaving the two end pieces intact as they hold the connection tabs.
After cutting away the power rail I could see absolutely nothing that could be causing the flickering, however with it removed the flickering stopped as expected.
The end sleepers where the track connection tabs are located are solid plastic and don't have a gap, so no way the high resistance join could be there.

I know in this discussion people have had success with opto isolated S88 modules. Without really knowing their differences I am guessing that it separates the S88 from the power feed earth and so isolates S88 from power that causes the flickering.

What I am saying is that this issue does have a cause and that cause is high resistance between S88 rail and the power rail below the track.
Unfortunately every sleeper except the end two has a big gap between the rail and the power rail below, so there are so many places where the high resistance leak can cause false S88 detection - which can make it an absolute PIA to fix.
If Marklin had made the plastic sleeper frame a solid piece (with no gap) then I suspect a lot of these issues would never have occurred.
Of course K track was never designed with S88 in mind back in the day. Not sure about C track but I don't believe it has this issue with the solid roadbed, so this problem typically only affects K track users.
modelling 1954 Germany (era IIIa)
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Offline Ross  
#16 Posted : 11 February 2020 07:15:02(UTC)
Ross

Australia   
Joined: 25/09/2006(UTC)
Posts: 706
Location: Sydney, NSW
Hi Eric/All,

I have had the experience using flex track where the contact rail was making contact with the metal centre rail below.
I found that the manufacturing process had embedded metal particles in the plastic that would make contact between the rail and the centre rail.
By removing the rail I used a multi meter to bell out the top of each sleeper with the centre rail and once I found the problem sleeper I was able to cut away some of the plastic so the rail no longer made contact.
There were so many problems with the length of track I discarded it for a new piece.

Ross
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