Cobalt Digital causing a shortcircuit

[Whislter65]

 

In the picture above I have three points. Each is attached to a Cobalt Digital point motor. Point 1 and point 3 have the Digitals the same way round and the wiring is as mentioned in the picture. Point 2 has the Digital round the opposite way and thus the wiring is the opposite as well.

 

The trouble I am having is point 2 with the point motor. As soon as I place the frog wire into the proper connector I get a short circuit through my NCE powercab. No matter which way the point blades are it always happens. I have checked to make sure I have all the IRJ's in the right place, and these are represented by red lines. The blue lines in the diagram are normal fishplates.

 

So what I have at the moment is my diesel trains going over point 2 without much trouble until they go slower then they splutter and stop. My steam loco's get stuck on point 2 by the frog every time. 

 

Could someone please point out what I have done glaringly wrong so I can rectify the problem before I lose the plot

 

regards

 

G

[traction]

The wiring on point 2 needs to be the same as point 3 surely?

I take it these are the rail feeds, so on point 3 the red is the top rail lower rail is black with the green as the frog wire.

Point 2 rails will be the same with the top rail as red and the lower rail as black other wise you will always get a short.

 

Thats if I'm looking and understanding this correctly!

 

Cheers

 

Ian

 

EDIT: if you follow it through, you get red on top rail of point 3 you should then have red on top rail of point 2 so that in the position shown taking the cross over it follows that you have red on the top rail of point 1.

Even though the Cobalt is the other way round you would still wire the switch the same way, it's only the motor that needs wiring the other way.

 

As shown it looks like you come from point 3 with red on top rail into point 2 with black on top rail, taking the crossing you would then have red on the top rail at point 1.

So it would go red-black-red hence short circuit.

 

I have not used or wired up a Cobalt so have no idea how the switching works so this could all be complete rubbish, but from the photo it does look like there is a crossover of power.

I think that makes sense, easy to do it than describe!

[Whislter65]

Hi Ian

 

I have added a picture of underneath which shows from the left point 1, then point 2 and finally point 3. As you will notice the point 2 motor is opposite way round but the wires are the same as the other two. I should of added this pictue in the first place instead of trying to draw it .......

 

[traction]

What I would do just to make sure of the internal switching is bell the frog connection to the DCC power connections.

 

I would drive the Cobalt all the way to one side then remove both of the power feeds, then put the meter into the frog connection then check the two DCC feeds to see which has continuity.

By looking at which way the point has been set and checking the continuity it should show which way the DCC feeds need to be, if thats all OK then I'm still trying to work it out!

So if you operate the point to take the crossover as shown in the first photo, you would want the red power lead putting in the connector which gives continuity with the frog connector.

(Hope that makes sense)

 

From that last photo it looks like you have a different set of feed wires powering the Cobalts and track obviously connected together somewhere else.

The two feeding the 'problem' Cobalt aren't crossed anywhere are they?

[Whislter65]

Turn cobalt point motor 2 around to match 1 and 3 and you will notice the wires are exactly the same. If I had the wires round the wrong way I would get a short all the time. I only get it once I place the frog wire into Cobalt 2.

[richard brown]

Looking at the picture I think you need to swap the wire on point 2 as I would expect red and black to always be on the side at all times

 

Richard

[traction]

Turn cobalt point motor 2 around to match 1 and 3 and you will notice the wires are exactly the same. If I had the wires round the wrong way I would get a short all the time. I only get it once I place the frog wire into Cobalt 2.

 

The only time you get a short is when you connect the frog, if the DCC power connectors are reversed then you would get a short every time, as the frog will always be set opposite the way you need it.

 

If the switch works how I think it does, you are powering the motor in the Cobalt with the DCC feed.

By switching these two wires will only effect which way it moves when you press normal or thrown on the PowerCab.

The problem is only when the frog is connected which to me means that the motor has moved all the way to it's limit in one direction but the DCC supply is switched round so the wrong polarity is being connected to the frog.

 

By testing which DCC  connector is actually connected to the Frog connection at both ends of travel of the Cobalt you will know for sure which way the power feeds need to be, and without any DCC connected no risk of any damage.

[Whislter65]

Ian

 

Argh the penny drops. Ok, first thing tomorrow I will do exactly as you have suggested. Hopefully that is it, Thank you

[traction]

No Problem, let us know how you get on.

Hopefully that is the issue.

 

Cheers

 

Ian

[Froxfield2012]

In your photograph, the green wire to point two seems to be in a different connector from the other two motors.  The frog wire should always be in the third connector, next to the track power wires.  I have just wired up about a dozen Cobalt digitals and the frog switch has worked reliably.  I have had issues making sure the track feed wires went to the correct connectors:  it seems that one needs to maintain the overall polarity and I THINK I did this by making sure that the feed from the rail furthest away goes to the connector furthest away (if you understand me?).  At least I think that is what I did, I will check later!!  In any event, it is a simple matter to reverse the track connections on a trial and error basis.

 

The main point I would make is to check that you have the frog wire in the correct connector.  If you don't then there is simply no polarity switch in place.

 

Richard

[traction]

Hi Richard,

 

I think that the green frog wire is only in the wrong connector because if it's placed into the correct one a short occurs.

By leaving it out then there will be no frog switching so no short can happen.

 

It looks and sounds to be whats happening.

[Froxfield2012]

On the basis that a picture is worth a thousand words, I just nipped out to the shed and took this of two Cobalts installed the opposite way round.  Despite my nightmare spaghetti wiring, they work!  Note that the two track wires (Yellow and Green) are reversed.

 

 

Richard

[Whislter65]

Froxfield

 

What I am interested to know is from your picture I notice one of the point motor arms has what looks like a screw on the end. If this is correct, has it been put in place to hold the arm in place?

 

 

In answer to the other question Traction (Ian) was absolutely right. As soon as I reversed the wires it all worked perfectly. Hours later and another 5 installed and it is still working

 

regards

[Froxfield2012]

Cobalts are supplied with this small screw (It is the one with a small flange/washer built in).  The wire goes in the top hole on the motor arm and the screw in the lower hole.  The screw is just to retain the wire so don't over tighten.  You will find this is covered in the instructions on DCC Concepts website and that came with the motors.  Whereas the polarity of the track wires I had to work out for myself by trial and error rather!

 

Richard.

[musketeer]

Sorry to resurrect a old thread, but I have a similar setup and issue than Whislter65, except that in my case it happens even tough the tracks aren't even powered.

 

I bought a number of Cobalt IP digital turnout motors, and started installing them on my new N-scale DCC layout, with Peco Electrofrog code 55 switches, out of the box.  I've installed and configured four of them, all the exact same way.  On the first two (which are toe to toe and a few feet of track apart), everything is working fine, but I'm getting a short circuit on the other two when the frogs are wired to the Cobalts.  These two are setup the same way as on Whislter65;'s first photo (except that in my case the turnouts are reversed: the straight line goes through the cross over while the diverging routes are sidings).

 

At this point, the tracks aren't powered yet.  The motors are connected to the same accessory bus, which is fed by my ESU ECoS command station.  All turnouts are on the same track, but isolated from one another by plastic joiners. As directed in the manual, the bus feeders are connected to the two leftmost terminals, and the frog wire to the third one (as in Froxfield2012's photo above).

 

When the blades are closed, no problem.  But when they're thrown, there's a short circuit as soon as (and as long as) the blade touches the diverging stock rail.

If I swap the power wires at the Cobalt's terminals, it's the opposite: no short when thrown, short when closed.  If I unplug the frog wire, the short goes away.

 

What is causing that short, since the tracks aren't even powered?  And why is it working fine on the first two turnouts?

[John ks]

Looking at Peco's turnout templates it looks like both point blades are joined electrically to the frog

When the point is straight both point blades are the same polarity, as shown below

 

 

I suspect that the point blades are slightly out of sinc with the switch in the cobalt

Because the movement required to move a N Scale point blades is very small it is possible for the blade to move to from straight to curved before the switch in the cobalt has changed

If this is the case then some very fine adjustment of the position of the cobalt will be required

 

Hope this helps

John

 

 

 

[Nigelcliffe]

Muskateer - as per John's post above.   Your choice is three fold:

 

 1 - don't fit the frog switch leads from the Cobalts because they are duplicating the wiring in the Peco turnout

 2 - mess about for ages finding the magic "centre" physical position where the Cobalt moves at exactly the same time as the Peco tie-bar, and thus a short does not occur (this may be impossible to get working reliably)

 3 - modify the Peco turnouts so they are like classical live-frog turnouts.  That means cutting the rails between blade and frog, plus wiring the remaining blade sections to their respective running rails.

 

A Peco N "live frog" is a funny hybrid turnout.  Its got a metal frog, but the blades are still switching the current like a dead-frog turnout.  Makes it simple to install most of the time, but it causes complications with more advanced and more thorough wiring methods.

 

 

- Nigel

[musketeer]

Ok, thank you both.  I simply won't connect the frog wire.  If some of my locos get in trouble, I'll consider modifying the turnouts on a case-by-case basis.

[musketeer]

I should have thought of it; the track is indeed electrically connected through the track's DCC power bus, which, though itself not powered yet, provides an electrical path between all the frogs on that track...  So depending on the directions of the throws on the points, if the polarity doesn't match on all of them, a short will occur.  One solution is to reverse the power wires on one turnout at a time. But I've tried all four combinations of wiring the two motors at fault, and out of the eight existing throw positions there's always at least one in which I get a short.  That might be because those two turnouts constitute a crossover.  As I'd rather avoid modifying the points (I've already ruined enough turnouts as it is), I'll probably end up keeping the frogs unconnected.