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Tortoise wiring conundrum.


Jeepy
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Hello,

 

I've tried doing a search on the forum but didn't find anything mentioning my particular puzzle so please accept my apologies if this has been presented before! Even a pointer or link to a particular thread may help a great deal.

Anyway, I am in the process of doing test runs with a Hornby peckett 0-4-0 to make sure my unifrogs are working ok because that's the loco that would be the most likely to show if the frogs are dead or alive I should think!

My set up is OO gauge Peco code 75 bullhead unifrog turnouts utilising tortoise machines wired through a home made control panel with a conventional DC power supply with DPDT ON-ON switches but the track power is DCC, in my estimation this shouldn't be having any effect on this particular problem I wouldn't have thought but I am a bit of a newbie so you never know! 

The Peckett is finding all the frogs dead and stalling but the frogs should be alive as far as I am concerned, i could be missing something here which i'm hoping someone might be able to shed a bit of light on please?

The turnout motors are working fine and I have run a wire from the frog to terminal 4 on the tortoise which I think should be the common terminal for one of the two internal auxiliary switches on the tortoise according to the diagram on the instruction sheet but as I said the frog still seems to be dead! So what i'm asking is have I done the right thing or am I missing something out here please? Thanks ever so much! 

 

Best wishes,

 

Jim.

 

P.S. I've just thought of something, should there be a track power supply to the tortoise to enable the internal auxiliary switch to operate? :dontknow:

Edited by Jeepy
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You say you have a wire going from terminal 4 to the frog, but don't mention if you have terminals 2+3 connected to the rails to feed the switch, or is that what you had realised with your afterthought?

 

Andi

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Ah! Yes, perhaps that's what is missing!?!? That was my afterthought! Should the track power be attached to terminals 2 & 3 then? Terminal 4 being the common for these and terminal 5 being the common for 6 & 7? Thanks ever so much, it doesn't actually mention this in the intstruction leaflet but i guess the diagram is self explanatory, this is my first experience of tortoise machines, it mentions the internal switches only being capable of switching 1 Amp maximum although the terminals can carry 4 Amps so i presume that would be ok? I am using an NCE Powercab for the track supply/DCC control, sorry if i seem a bit clueless! Thank you! 

 

Best wishes, 

 

Jim. 

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15 minutes ago, Jeepy said:

Ah! Yes, perhaps that's what is missing!?!? That was my afterthought! Should the track power be attached to terminals 2 & 3 then? Terminal 4 being the common for these and terminal 5 being the common for 6 & 7? Thanks ever so much, it doesn't actually mention this in the intstruction leaflet but i guess the diagram is self explanatory, this is my first experience of tortoise machines, it mentions the internal switches only being capable of switching 1 Amp maximum although the terminals can carry 4 Amps so i presume that would be ok? I am using an NCE Powercab for the track supply/DCC control, sorry if i seem a bit clueless! Thank you! 

 

Best wishes, 

 

Jim. 

Yes,  your guess on the terminal numbers is correct. 

Assuming you have insulating joiners fitted on the frog rails of your points as per recommended DCC practice (If not then holler now and we can assist!) then the switching contacts of the Tortoise should not be switching under load so will take whatever current your DCC system is putting on the track with no issue. 

 

Somewhere I've got a picture of the PCB of a Tortoise which shows the terminals and how they connect into the switch. If i can find it I'll post it as it does help to see what's going on inside that green box.

 

edit: Found it

tortpcbm.gif.e5dfc25b5417bd48e44bd19fb8a659d2.gif

 

Andi

Edited by Dagworth
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Waheey! That sort of makes sense now, you need something for the switch to switch if you get my meaning! LOL! It's obvious now I suppose but I was a bit dubious about putting track power to the tortoise for fear of blowing it! Live and learn! :fool:

I have metal rail joiners all round as I was led to believe insulating ones weren't really necessary with unifrog on DCC, (The design of the unifrog is such that it's only the very tip and not the whole frog)  unlike the usual electrofrog on which there is the possibility of a short occurring.....problem is I've glued the turnouts down now and it would cause a real headache to replace with insulating joiners but I guess I could always use a slitting disc to create a gap on the frog rails if I get any problems? Every section of track has droppers soldered to it including every turnout so it wouldn't have any adverse effect if I cut them in situ I suppose...…..This is a kind of eureka moment for me! Thanks ever so much! Also thank you for posting the picture,

 

Best wishes,

 

Jim.

Edited by Jeepy
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Another afterthought!..... How do those people get on who have 5 Amp or even 10 Amp control systems? Doesn't putting the track supply through the tortoise internal auxilary switch burn them out? Just asking! Lol! 

 

All the best, 

 

Jim. 

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1 hour ago, Jeepy said:

Another afterthought!..... How do those people get on who have 5 Amp or even 10 Amp control systems? Doesn't putting the track supply through the tortoise internal auxilary switch burn them out? Just asking! Lol! 

 

All the best, 

 

Jim. 

edit...ignore I misread the question

Edited by pheaton
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26 minutes ago, pheaton said:
1 hour ago, Jeepy said:

Another afterthought!..... How do those people get on who have 5 Amp or even 10 Amp control systems? Doesn't putting the track supply through the tortoise internal auxilary switch burn them out? Just asking! Lol! 

 

All the best, 

 

Jim. 

This is why a lot of people recommend a separate accessory supply, which is separate from your main supply, and in theory....should run at a lower amperage, but the design of the switch in that the fingers are dragged across rather than lifted should keep spark erosion to a minimum. However if you take a knackerd tortoise apart you will see its a fairly well built switch.

 

Eh ?    I really don't understand the answer.

The accessory switch is there to switch the track supply.    Its nothing to do with accessory supply, which will operate the tortoise motor.     

 

The contacts on the tortoise (in most cases) will move when there is no current flowing through the switch because there isn't a loco sitting on the frog when the turnout is changed (no loco on the frog, no current flowing).   So there are not a lot of "make/break" sparking events when the switch is moved with current flowing. 

 

The max current, and max-arcing may occur when there is a short at a frog.  Many DCC systems attempt to re-connect themselves after a short.   If someone drives into an incorrectly set turnout, and causes a short, then corrects it by throwing the turnout, then the contact switch may be subjected to the maximum current the layout can deliver at the time the contact opens.

 

But, most of the time, the closed (non-moving) contacts of the switch are only carrying (at most) the max current of the locomotive getting its power via the frog.  That is usually a small fraction of what the DCC system can deliver. 

 

 

 

That said, there are layouts which have used Tortoises for a long time, with a DCC system, where the switch contacts in the Tortoise have started to fail.  And that becomes extremely annoying in operating the layout.   There is a fairly simple modification to a tortoise where an external microswitch can be fitted to a piece of aluminium angle to replace the internal contacts.     The large Burntisland-1883 layout has gone through most of its tortoise motors to make this change.  Burntisland's DCC system is a 5-Amp Lenz unit.  
However, it won't be possible to give an A-B comparison because we've made other robustness changes to Burtisland's wiring at the same time,  so Tortoise now have microswitches for frogs, there are 1.5A power district cutouts (so max current at a frog is 1.5A, rather than 5A), the power district structure changed,  plus other changes. 

 

 

- Nigel

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3 minutes ago, Nigelcliffe said:

 

Eh ?    I really don't understand the answer.

The accessory switch is there to switch the track supply.    Its nothing to do with accessory supply, which will operate the tortoise motor.     

 

The contacts on the tortoise (in most cases) will move when there is no current flowing through the switch because there isn't a loco sitting on the frog when the turnout is changed (no loco on the frog, no current flowing).   So there are not a lot of "make/break" sparking events when the switch is moved with current flowing. 

 

The max current, and max-arcing may occur when there is a short at a frog.  Many DCC systems attempt to re-connect themselves after a short.   If someone drives into an incorrectly set turnout, and causes a short, then corrects it by throwing the turnout, then the contact switch may be subjected to the maximum current the layout can deliver at the time the contact opens.

 

But, most of the time, the closed (non-moving) contacts of the switch are only carrying (at most) the max current of the locomotive getting its power via the frog.  That is usually a small fraction of what the DCC system can deliver. 

 

 

 

That said, there are layouts which have used Tortoises for a long time, with a DCC system, where the switch contacts in the Tortoise have started to fail.  And that becomes extremely annoying in operating the layout.   There is a fairly simple modification to a tortoise where an external microswitch can be fitted to a piece of aluminium angle to replace the internal contacts.     The large Burntisland-1883 layout has gone through most of its tortoise motors to make this change.  Burntisland's DCC system is a 5-Amp Lenz unit.  
However, it won't be possible to give an A-B comparison because we've made other robustness changes to Burtisland's wiring at the same time,  so Tortoise now have microswitches for frogs, there are 1.5A power district cutouts (so max current at a frog is 1.5A, rather than 5A), the power district structure changed,  plus other changes. 

 

 

- Nigel

your right Nigel I misread the question

 

 

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But, most of the time, the closed (non-moving) contacts of the switch are only carrying (at most) the max current of the locomotive getting its power via the frog.  That is usually a small fraction of what the DCC system can deliver. 

 

Thank you, this sort of makes sense to my fuddled brain and inexperience in these things! 

 

 Best wishes, 

 

Jim. 

 

(Why do i have to keep manually deleting everything before i can type what i need to?!?!?) 

Edited by Jeepy
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I think i get it now..... The Amperage is more to do with the capacity rather than the actual current or Voltage flowing through!?!?

(You might have guessed I'm not an electrician!) 

Edited by Jeepy
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I connected extra droppers to all the tortoise units from the track bus to terminals 2 and 3 and with the wire from the frogs to terminal 4 all is working fine! Had shorts on a couple of the turnouts when the loco reached the frog but I just swapped the wires to terminals 2 and 3 around on these and that sorted it, mainly I think due to the fact they were on turnouts forming crossovers so obviously the polarity had to be changed on those as they were opposite each other, i'm learning! I know a little bit more about tortoise units now! LOL! Thanks to everyone who contributed,

 

Best wishes,

 

Jim.

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As an irrelevant, but hopefully reassuring, aside, I had a bit of a realisation the other day. People worry about the fact that tortoise motors are in effect powered all the time. I have about 15 tortoises, installed about 2006/7. So was the power source, a simple, cheap plug in transformer. It has never been switched off, supply outages apart, in all that time. I turn off my Digitrax system between running sessions, but not the transformer to the point motors. So I can attest to tortoise motors remaining powered up for more than 12 years without any casualty. 

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20 minutes ago, Oldddudders said:

As an irrelevant, but hopefully reassuring, aside, I had a bit of a realisation the other day. People worry about the fact that tortoise motors are in effect powered all the time. I have about 15 tortoises, installed about 2006/7. So was the power source, a simple, cheap plug in transformer. It has never been switched off, supply outages apart, in all that time. I turn off my Digitrax system between running sessions, but not the transformer to the point motors. So I can attest to tortoise motors remaining powered up for more than 12 years without any casualty. 

 

Very reassuring.....Thank you! I have a plug in transformer supplying the tortoise units separate to the DCC system too, with a power distribution board so the same transformer will be supplying my electromagnets (For DG couplings) which are installed but not yet connected and eventually servos for the signals are planned.

All I was expecting the DCC to do was control the trains but as I've found out the tortoises need a track supply if you want to liven the frogs! I'm on quite a large learning curve at the moment so all advice and reassurance is most welcome! Thanks ever so much!

 

Best wishes,

 

Jim.

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A quick suggestion:

When I'm doing point wiring (or other polarity sensitive) I use clip leads (test leads with alligator clips) on the wires until I know I have them the right way round.

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