Block wiring diagram help

 
  miktrain Deputy Commissioner

Location: Adelaide SA
Operator errors are a given. If a train is crossing blocks and momentarily receives current from 2 power sources, how likely is it of burning out the train motor? Are there "easy to install" fail safes I can install in the circuit - similar to switches in a modern home that trip if a spike is detected?
The likelyhood of a motor burning out if it receives power from two different controllers is about zero.  It is the controllers that will need to be protected in this case.  The wheels and pickups will effectively bridge the two sections, connecting them both together, so the motor is fine but the two controllers must be able to survive having their outputs connected together.

It is for this reason that it is important to use separate power supplies, completely isolated from each other (as per your last diagram), to prevent unexpected current flows when the train crosses between controllers.

If you choose your controllers well (i.e. with comprehensive output protection) then you should be OK.

No doubt you could also add circuit breakers to each section output for extra protection.  I haven't researched protectors for DC (I'm planning to use DCC) so I will defer to others for advice in this area.
Parkeston
If you leave the loco sitting there it will may be jittering between the two blocks which will not do it any good and may well do damage, so fix the problem asap.

The controllers should be OK if they have good heat sinking.

Yes, separate supplies but the controllers should be connected at the negative of the rectifiers (the earth symbols on the diagram) this will get those locos with diagonal pick-ups (Lima, Hornby etc) smoothly across the blocks. ALL blocks MUST be double isolated, NO common rail.

The controllers chosen have output diodes so should be fine provided they have good heat sinking.

Tony

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  miktrain Deputy Commissioner

Location: Adelaide SA
It seems as though this thread has just about run its course. Thanks to all who participated, it's been extremely useful.

I have a separate DC supply for structure lighting so I guess I can just run the LEDs off this. I may have mentioned earlier, since we are doing a video diary of the entire build I'll certainly be dedicating a chapter to the wiring - try and pass on what I've learned to the next boofhead! I'll post it here when done.
gombul

Use the DC supply.

As an aside check your switches as most of that type, switch opposite ie when you switch up the bottom is connected and if you switch down the top is connected. It is not a problem just wire it "backwards", this catches many newbies.

Tony
  Parkeston Station Staff

Yes, separate supplies but the controllers should be connected at the negative of the rectifiers (the earth symbols on the diagram) this will get those locos with diagonal pick-ups (Lima, Hornby etc) smoothly across the blocks.
miktrain
Something was bothering me about connecting the controllers at the negative of the rectifiers.  Yes, this would help the locos with diagonal pick-ups, but in the case of operator error (already established as a given) and depending on the switch settings, there is the possibility of ending up with 24 volts across those same diagonal pick-ups as the loco crosses into the next block.
  miktrain Deputy Commissioner

Location: Adelaide SA
Yes, separate supplies but the controllers should be connected at the negative of the rectifiers (the earth symbols on the diagram) this will get those locos with diagonal pick-ups (Lima, Hornby etc) smoothly across the blocks.
Something was bothering me about connecting the controllers at the negative of the rectifiers.  Yes, this would help the locos with diagonal pick-ups, but in the case of operator error (already established as a given) and depending on the switch settings, there is the possibility of ending up with 24 volts across those same diagonal pick-ups as the loco crosses into the next block.
Parkeston
No, that is the reason for doing it there and not using a common rail, it prevents the voltage adding that you are rightly concerned about as all voltages are referenced to that one point.

The important bit here is that there is only one common, all blocks must be double insulated, no common rail.

Here is diagram of the way it is https://ozfreemo.com/members/index.php/Tony/Help-Files/current-paths-01

The blue lines are where a short happens between the controllers this is only flowing through the wheels and pickups (still not good)
The red and green are what you are worried about and as you can see they are both the same (unless the controllers are set to different speeds (voltages)

This one is for common rail https://ozfreemo.com/members/index.php/Tony/Help-Files/current-paths-02

The blue line is where a short happens between the controllers as above this is only flowing through the wheels and pickups but note that there is a difference of 24 volts
The red and green are what you are worried about, only one will be active depending on the way the loco is wired and as you can see they now both have up to +/-12 volts across them and through your loco.  


We have both our permanent layout and display layout "Paradigm" wired that way by me and all future ones that I and Aaron do will be done that way. We run both DC and DCC on those layouts at the same time (in different blocks), something that all the nay sayers firmly believe and pronounce "Can't be done" and we can, and have, run from one to the other but that does require a little variation in the wiring that is not part of this discussion as you are only looking at DC.

Tony

Edit on link to update to new location
  Aaron The Ghost of George Stephenson

Location: University of Adelaide SA
The important bit here is that there is only one common, all blocks must be double insulated, no common rail.
miktrain
Hmmm, yes, something I seem to spend too much of my life doing. Explaining that in the electrical world we call it a common because it is common to many things, we do not call them common because there are lots of them...

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