help please with hornby turntable to dcc.

[gragrahadea]

i am considering buying a horrnby turntable,how do you wire it up for dcc.many thanks.

[Chrissaf]

The Hornby guide for converting the TT is on this web site - you can see it here. Note however, that many on this forum dispute that Hornby's instructions are the best way to do the conversion. Search the forum for R070 and/or Turntable to find the numerous threads on this forum devoted to the Hornby R070 turntable.

[LMSFan72]

I used the Hornby guide and it works great: 2 things to watch for though.

1. make sure the rails on the turntable bridge  are central so they don't catch the rails on the "roads" as the bridge turn otherwise they will short 
2. If you wire the bridge wires from the middle of the turntable to a bus note that at some point as the bridge rotates the polarity reverses so you need to check that if you have a bus feeding power to all "roads" you need to switch the + and -  on about half of the roads

[St1ngr4y]

I used the Hornby guide and it works great: 2 things to watch for though.

1. make sure the rails on the turntable bridge  are central so they don't catch the rails on the "roads" as the bridge turn otherwise they will short 
2. If you wire the bridge wires from the middle of the turntable to a bus note that at some point as the bridge rotates the polarity reverses so you need to check that if you have a bus feeding power to all "roads" you need to switch the + and -  on about half of the roads

If you DON'T use the Hornby guide, then point (1) does not apply.

Ray

[Fozzy Bear]

Be aware that  there is an error in the Hornby instructions. When connecting the decoder to the motor, hook it up the opposite of what the instructions say as it will run backwards.

[mjb1961]

I used the Hornby guide and it works great: 2 things to watch for though.

1. make sure the rails on the turntable bridge  are central so they don't catch the rails on the "roads" as the bridge turn otherwise they will short 
2. If you wire the bridge wires from the middle of the turntable to a bus note that at some point as the bridge rotates the polarity reverses so you need to check that if you have a bus feeding power to all "roads" you need to switch the + and -  on about half of the roads

Hi lmsfan72 ,point 2 ,I had to do this and I have only 2 roads to engine sheds but I have found that if I have a loco with sound on the bridge the sound will continue to play until it passes either one of the roads and moves in between them ,do you know if there is a way to solve this so the sound stays on ,,,,,thanks mjb

[Chrissaf]

do you know if there is a way to solve this so the sound stays on

.

You would need to further modify (if necessary) the TT to make the bridge completely isolated electrically and feed the DCC power to it via a Reverse Loop Module (RLM).

For more information check out Brian's TT pages on his web site - click this link

[St1ngr4y]

I used the Hornby guide and it works great: 2 things to watch for though.

1. make sure the rails on the turntable bridge  are central so they don't catch the rails on the "roads" as the bridge turn otherwise they will short 
2. If you wire the bridge wires from the middle of the turntable to a bus note that at some point as the bridge rotates the polarity reverses so you need to check that if you have a bus feeding power to all "roads" you need to switch the + and -  on about half of the roads

Hi lmsfan72 ,point 2 ,I had to do this and I have only 2 roads to engine sheds but I have found that if I have a loco with sound on the bridge the sound will continue to play until it passes either one of the roads and moves in between them ,do you know if there is a way to solve this so the sound stays on ,,,,,thanks mjb

Hi MJB,

The R070 has a bridge position where there is a dead spot electrically. This picture shows where that is, and a sound loco will lose its sound as it passes through this position - only for a second or two, a few degrees of rotation, and there is nothing that can be done to prevent this. In your case, however, you may have been unlucky enough to select as your two engine shed roads, one road on each side of this position, which I've marked as either A & B or X & Y on the picture. If this is the case, then maybe if you move the whole tyurntable, say, 90 degrees either way, so that moving your bridge between the two engine shed roads does not pass the bridge through this position, then the sound on the loco will stay on.

 

/media/tinymce_upload/5547e1885508f745e38c127421ce39fe.jpg

 

This dead spot occurs, by the way, at the point where polarity changes, so on track X the +- are opposite to track Y, similarly with tracks A & B.

I hope this helps.

Ray

[mjb1961]

I used the Hornby guide and it works great: 2 things to watch for though.

1. make sure the rails on the turntable bridge  are central so they don't catch the rails on the "roads" as the bridge turn otherwise they will short 
2. If you wire the bridge wires from the middle of the turntable to a bus note that at some point as the bridge rotates the polarity reverses so you need to check that if you have a bus feeding power to all "roads" you need to switch the + and -  on about half of the roads

Hi lmsfan72 ,point 2 ,I had to do this and I have only 2 roads to engine sheds but I have found that if I have a loco with sound on the bridge the sound will continue to play until it passes either one of the roads and moves in between them ,do you know if there is a way to solve this so the sound stays on ,,,,,thanks mjb

Hi MJB,

The R070 has a bridge position where there is a dead spot electrically. This picture shows where that is, and a sound loco will lose its sound as it passes through this position - only for a second or two, a few degrees of rotation, and there is nothing that can be done to prevent this. In your case, however, you may have been unlucky enough to select as your two engine shed roads, one road on each side of this position, which I've marked as either A & B or X & Y on the picture. If this is the case, then maybe if you move the whole tyurntable, say, 90 degrees either way, so that moving your bridge between the two engine shed roads does not pass the bridge through this position, then the sound on the loco will stay on.

 

/media/tinymce_upload/5547e1885508f745e38c127421ce39fe.jpg

 

This dead spot occurs, by the way, at the point where polarity changes, so on track X the +- are opposite to track Y, similarly with tracks A & B.

I hope this helps.

Ray

Hi  ST1ngr4y,yes my two engine shed tracks are where you have marked as A and B ,I never knew about the dead spots but I came across the polarity change by accident really ,anyway I'll give your suggestion a go ,thanks for your reply ,,,,,mjb

[Fishmanoz]

Let's look a little further at how this TT works and better ways to convert it.

 

For a start, the connections to the bridge are via a slip ring arrangement which means half the outlets are at reverse polarity (180 degrees out of phase with) the others - see Brian Lambert that Chris has given you a link to.

 

The first part of DCC conversion is to run the bridge motor via a loco decoder.  This bit is simple, just connect up the decoder as you would in a loco (red and black wires to DCC power and orange and grey to the motor, noting Fozzy bear's advice about which way orange and grey are connected).

 

Then the bridge must be isolated from the powered input track (must be powered as it connects the TT to the layout) otherwise it will short out every time it rotates as at one point this means that rail A on the inlet is connected to rail B on the bridge ( not to be confused with Ray's outlets A and B).  So Chris's point about isolating the bridge completely is fundamental to DCC conversion.  You can't do it without isolation.

 

So how does Hornby suggest you do this - butcher the TT by removing the connectors at each end of the bridge.  Yes this achieves the result, but is the butcher's sledge hammer method.  It means that you now have to power every outlet from the TT, with the correct polarity (or use an RLM as Chris says) as the simple method of the power coming from the bridge when it aligns with the output no longer applies with those connections removed.

 

What is a more elegant method - gap the inlet track, both rails, between the bridge connections under it and the TT end.  By gapping, I mean cut the rails and glue a small piece of plastic card in the gap to make sure the rails can't move and reconnect.  Now the pieces of rail between gaps and the TT are dead and no short occurs when the bridge rotates.  So your problem on the inlet has been solved.

 

What about the outlet tracks you say, do I have to gap them too?  The answer is not if they don't connect back to the layout or the DCC bus.  This will be the case if they are just dead end sidings leading to engine sheds or storage.  However, if they lead back to the layout, they must be gapped too, and the polarity must be correct (else you will need an RLM and an isolated section longer than your locos).  Then, while you may have many outlets, very few if any will connect back to the layout, they will be mainly dead end sidings.

 

What are any limitations of the gapping method?  Well, the sidings are dead except when the bridge is turned to them.  So no sound will be coming from sound locos until the bridge is turned to them.  But is this really a limitation?  You put the locos in the sidings to close them down, leave the bridge turned there until this is complete, and turn it back there later to start them up again.  

 

Now ow you should understand more about how the TT works, and you have an alternative to the Hornby method of adapting it to DCC.

[Fishmanoz]

Sorry about the Now ow in the last line above but the Edit function is playing up (again Adam) and won't let me get to the bottom part of my post to fix it.  It should just be Now.

[St1ngr4y]

Hi Fishy,

For situations where the R070 TT has only ONE road leading to the main layout, and all of the other USED roads are dead-end sidings, I still believe my method is far easier, and if you don't mind I'll go over it briefly.

1. DON'T remove the brass contacts at each end of the TT bridge as per the Hornby instructions.

2. Underneath the TT, disconnect the wires from the inlet road, and connect them directly to the DCC track bus. You need to get the polarity correct so that when the bridge is aligned with the road to the rest of the layout, the polarity of the bridge is the same as the approach track from the layout.

3. On each piece of inlet track used (including the one leading to the rest of the layout), remove the metal rail joiner and replace it with an insulating rail joiner. Put an IRJ on the other rail also so that there is a break in both rails at the outside end of each inlet track. At this point, every inlet track is dead except those aligned to the bridge. Also it doesn't matter if the wrong bridge rail momentarily makes contact with an inlet rail as it passes.

4. Connect each siding (both rails) to the DCC bus. Again, polarity is important, and as has been mentioned earlier, half the roads will have one polarity, and the others the opposite. Careful thought and maybe a bit of trial-and-error (or a multimeter) should be used to get these connections right.

Sound locos can have their sound on in the sidings, as they are always "live". As I mentioned earlier, the only dead spot is on the TT bridge when it passes through the polarity changeover. The only operational consideration is that a loco approaching the TT should not be stopped too close so as to straddle the IRJs while the TT is rotating.

Ray

[Fishmanoz]

I can only agree Ray that this method will work perfectly well too.  And you don't have to power the sidings if you don't need them working when the bridge isn't turned to them and, in this case, you don't need IRJs on them, only on the inlet.  This will allow the method to be used by people who don't have a DCC bus.

 

There isn't a perfect solution for this TT as it wasn't designed with DCC operation in mind, but there is more than one compromise to achieving an acceptable solution.

[PJ_model_trains]

This thread is very interesting and includes a lot of very useful information in it.   😉

 

My thoughts are that as more and more of us purchase loco's with sound, or increase our stock of loco's with sound, we will want to hear the sound 'where ever' our loco(s) are. Coming to the bridge, on the bridge or in the roads beyond the bridges. Loco's may be in engine sheds being worked on, they may be just warming up, I will want to hear the sounds.

 

So from the options suggested, for me, I feel Ray's suggestion seem the best.  😀

[37lover]

Completely off topic.

PJ - I've just looked at your Layout Gallery link and must congratulate you on such interesting and informative photos. Really good to see someone sharing how they do things. I'm not saying my 'builds' would be interesting but I never take photos between stages which is a very important consideration when trying to explain [justify!] how things were put together. Well done. 

[96RAF]

Although not a Hornby unit my DIY TT follows the above advice - it has all the sidings wired direct to the same DCC 'polarity' as the in-road.

 

The TT bed (in my case powered through a 1/4 inch stero jack which is used as the pivot - but the principle is adaptable to any slip ring type of system) is wired from the in-road to the centre terminals of a DPDT ON-OFF-ON switch, the selection, and hence output, of which sets the bed polarity to either normal (same as in-road) or reversed (for 180 swing) as required.

 

As the switch has a centre OFF I can isolate the bed if necessary, but I find when a sound loco in on the bed if I flip the switch smartly from one ON to other ON the loco does not drop its sound.

 

I also have a pair of red/green bi-colour LEDs mounted on the ends of TT bed which indicate bed polarity so I know if I need to flip the switch or not.

 

I know its not DCC, nor is it automatic, nor is it motorised, but it works fine and serves me well at present.

 

Here's a picture:

http://www.rmweb.co.uk/community/index.php?/gallery/image/70199-diy-turntable-pivoted-on-a-14-stero-jack-plug/

 

[PJ_model_trains]

Completely off topic.

PJ - I've just looked at your Layout Gallery link and must congratulate you on such interesting and informative photos. Really good to see someone sharing how they do things. I'm not saying my 'builds' would be interesting but I never take photos between stages which is a very important consideration when trying to explain [justify!] how things were put together. Well done. 

 

Thank you 37Lover

 

I believe it is always good to share ideas. I discussed the fishing lake on RMWeb and the first few message sort of shot me down, I tried it and scrapped it one said, looked ok on paper rubbish on layout. Ended up like a puddle another said. There were some nice comments at the end. The aim isn't looking for credit, it is just sharing ideas, if one person likes the idea and does it I am happy I have helped.

 

It has been a frustrating period waiting for a chippy to fit a wall plate and put my layout boards on the wall, so with one section on the dinning room table I got started. Not a live wire on it 'yet', no DCC Bus, etc, etc. Just what you see on top. I am hoping the guy will fit the wall plate ad boards for me this week then I can start to get thinks working.  😉

 

[LMSFan72]

This thread is very interesting and includes a lot of very useful information in it.   😉

 

My thoughts are that as more and more of us purchase loco's with sound, or increase our stock of loco's with sound, we will want to hear the sound 'where ever' our loco(s) are. Coming to the bridge, on the bridge or in the roads beyond the bridges. Loco's may be in engine sheds being worked on, they may be just warming up, I will want to hear the sounds.

 

So from the options suggested, for me, I feel Ray's suggestion seem the best.  😀

Well, I agree, learning a lot too! I don't have sound yet but will very shortly... so this bridge problem is interesting and i will soon experience it. I have a couple of thoughts

1. Increasing the stay alive capacity on the decoder so it stays alive through the polarity swing (I have no idea on how long that would need to be yet, nor, if it would even work)

2. Fit a sound decoder to the turntable so that it can mask the interruption through the polarity swing.

[96RAF]

@LMS

 

re point 2.

What 'background' sound did you have in mind as all the 1:1 scale TTs I have seen operating were very quiet with the overbearing noise being the beast on the table.

Maybe a selectable escaping steam hiss or diesel fan/compressor or similar triggered by a sensor to play for a few seconds as the polarity shift occurs would work.

[St1ngr4y]

@mjb1961

Don't forget that, if your engine shed roads are A & B, at the moment they must be wired with their polarities opposite to each other. If you rotate the whole TT through 90 degrees, then ONE of these roads will need to change its polarity so that they both have the same polarity.

Ray

[RB51]

Possibly a daft thing to say - but would a RLM deal with the polarity change? Maybe a sledgehammer to crack a nut, but just thought I'd ask. I dont have a TT. R-