Worrying Flash from Point motor to Rail....

[96RAF]

I am in process of rebuilding my layout from end-to-end to roundy-round and this involves complete rewiring of points motors according to my long established dual DC/DCC points switching method - see this diagram:

 

/media/tinymce_upload/0fe1e9f5f265a6f8c1e2d19b19404cb5.gif

 

 

As usual RM will have Elite controlling locos on track and eLink will ackle the points through a separate bus per the diagram above.

 

So far the relay panel has been installed and tested on a DCC signal and it works from an RM on-screen selection via the eLink and Hornby accessory decoders, although at this stage there were no motors installed for it actually operate. I.E. the DCC side correctly pulls in the associated relays.

 

After an afternoon wiring up, I have got to the stage of installing the Hornby surface mount solenoids and wiring them back to the relay board. First tests prove that I got the paired solenoids wired correctly as they both throw the correct way when selected.

 

At this stage (fortunately I think) no DCC controllers were wired up, eLink was not connected to the relay panel and Elite was not connected to the tracks

 

I had one solenoid motor that was sticky in one direction only and as I was operating it back and forth on manual switching I saw a flash from that motor to the nearest rail when switched to the bad side.

 

Ordinarily I could easily have missed this and if I had been using a single bus DCC for locos and accessories I may never have known about it, but the thought of a CDU output arcing a good 10mm from the point motor to the rail really does have me worried. What could have happened if the Elite had been active on the rails doesn't bear thinking about.

 

The fault leads me to believe that one side of the motor coil wiring has been compromised and maybe a high resistance common connection led to the flashover to the nearest earth point - the rails.

 

Any constructive comments welcomed.

 

 

[2e0dtoeric]

You don't say what kind of solenoids they are/were, Hornby track mounted, Hornby or Peco remote - on top or under the board, Seep's.

The only way I can see any arc occurring is if the track itself is connected somewhere to the CDU output, otherwise there can be no circuit. So maybe you have a track dropper wire going to the CDU, and the point motor return connected to the track??

Perhaps Chrissaf can throw another idea into the hat when he sees this?

[96RAF]

Sorry about that 2E.

Hornby surface mounted motors on top of the board - the little black ones with the stainless steel baseplates.

No track droppers, only a few links from loop to loop, then direct to Elite Track terminals.

Points and Track are totally separate in theory and practice, but I will draw out the circuit schematic again and see if there is any chance of the CDU pos and neg bus getting a look at the tracks, but I can't see the rails being in any circuit as they were not connected to the Elite at the time.

My controllers usually sit on all metal shelves and it is a very remote possibility that a stray wire could be touching a shelf.

[2e0dtoeric]

Unplug all the 240v supplies, then get the multimeter out, and start poking! (Behave, I meant with the meter probes!).

[Chrissaf]

My controllers usually sit on all metal shelves and it is a very remote possibility that a stray wire could be touching a shelf.

.

When I first saw this original post, I didn't feel that there was any value I could add as I couldn't see any issue with the original wiring diagram, and still can't.

.

Applying pure diagnostic logic.

.

• We know that Rob used the above wiring diagram on his first layout without issue, so it can't be a fundamental design flaw.
• So it has to have been an issue with replicating the wiring design on the new layout.
• Assuming wires have been run and awaiting termination, it is logical to diagnose that the flash over was caused by a wire touching something somewhere. Or something mis-terminated.
• The metal shelving is a possibility.

.

Only Rob is in a position to assess what might have been touching as he has the 'eyes on the ground' so to speak.

[96RAF]

First thing was no wires were touching the metal shelves.

 

After much disconnecting of wiring to isolate the known good bits, I went back to the meter and checked continuity across all likely suspects and I ended up at a duff motor - yes you guessed it was the one that flashed. It was indicating a short but not all the time.

 

Inside these things is a nice mechanism, but it is spoilt by a mess of spare coil wire leading to the tiny pcb that leads the three circuit wires out to your layout. The coil wire is varnished copper and by the looks of it where the excess between the solenoid coils and the pcb was stuffed into the casing the varnish must have cracked or rubbed off or whatever, but it was shorting on one side of the solenoid to the s/s baseplate, with a very slight sooty witness mark, hence why it was sticky in one direction.

 

I spliced in a new motor and all is well - a satisfy thunk each way now, so its case closed.

 

During this exercise I did find a wiring logic error and had to correct it. Upon manual switching the points all operated correctly so I knew the relay panel was wired correctly, but from RM using the acc decoders #1 point fired #4, #2 fired #3, 3# fired #2 and #4 fired #1, so I had a bit of wire swapping to do to put that right. That was really odd as all the wiring that had been removed still had its ID stickers and I wired them according to those. Maybe I mis-labelled them originally and corrected the wiring but not the lables.

 

 

Now its time for my home made hand operated turntable to be wired up -  again using my tried and tested wiring diagram that switches the table bed polarity and has LEDs to tell you if its contra-polarity or OK before you drive your train on/off it. The TT revolves on a 1/4" stereo jack plug, which also passes current to the bed.

[2Gingers]

Just been looking at RAF96's DC/DCC point wiring diagram,  one thing I cant understand is what is the 2 pole 6 way rotary switch for?.

Apart from that it is a system which I intend to use.

Many thanks -

[Chrissaf]

The rotary switch in RAFs diagram allows six point motors to share one pair of push switches. Lets say for example you had 18 points. Then you would have three rotary switches and three push button pairs. You could of course have 18 push button pairs and do away with the rotary switches altogether.

.

Robs (RAF96) diagram only shows one of each component item to aid the clarity of the drawing.

.

PS - I should have added that Rob will be along in a minute to confirm once he has had his morning coffee. Which he has now done.

[96RAF]

Of course you can replace the rotary switch/PB bit with any other manual switching/selection arrangement, such as passing contact switch, sprung to centre off switch, probe and stud, etc.

 

Pos and Neg buses by the way are just terminal strips used as collectors.

 

Chris was spot on with the 18 points - here is the original panel

http://www.rmweb.co.uk/community/uploads/1295903197/gallery_7193_1326_14599.jpg

[2Gingers]

Thanks Chris for your explanation,  I now understand why it shows other circuits coming off the positive bus " To other p/b switches "

Thanks for your help.

[2Gingers]

Thank you for your reply RAF96 and the photo link, It looks very impressive.

I like the idea of being able to operate points manually outside of the Elite/Railmaster control. 😀

Many Thanks for your help.