Block wiring diagram help

 
  gombul Station Master

Location: Canberra, Australian Capital Territory
For the sake of clarity I've persisted with the 'pink paper' sketch as I think showing a few examples make this clearer. Hopefully the text on each image is clear. While non conventional, I find the colours help me analyse current flow.

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  apw5910 Deputy Commissioner

Location: Location: Location.
(sorry wandering of track a little) I cannot remember why we did it those many years ago.But In the very early days of MMRS when I was just starting out a PMG (Telstra?) tech was pretty senior in that Club. He provided heaps of scrap wire, relays and PMG "type" intelligence and dominated the layout wiring at MMRS.
First thing we were all taught was to use two transformers and a common return. One transformer pumped out power to the +ve side and a second identical and matched transformer supplied the -ve side. We bought masonite boards painted grey pre drilled for a circle of brass cheese head screws. To these we measured various links of jug element replacement wire, straightened in places to attach to the backs of the cheese heads via washers and two nuts each. A nice handle, center shaft with wiper was loosely fitted to a middle bearing. The off position was unconnected to the jug element and resistance changed as the wipers moved across two cheese heads at a time
Today I would not go that way, but 50 years ago almost everybody used the "Allan Dowel" (?) wiring system, single strand pmg wire ( and all its problems) as well. ugh!!  I still see old layouts still using it, but would love to be reminded of why we used it in the first place? Was it a legacy of three rail systems?
Rod Young
comtrain
The system you describe didn't need a reversing switch at all, which was the advantage when high amperage toggle switches were expensive (especially DPDT types). The "common return" can be thought of as 0V at all times, with the other traction power wire varying from -12V to +12V depending on where the rheostat was set. Bit like audio signals or RF in coax. I had an old Tri-ang controller with a big red knob that was "centre-off" with a split power supply that did this as a child. The transformer had a 15V-0-15V centre-tapped winding and a selenium bridge rectifier.

I like single strand PMG wire, although I get it from stripping cat-5 cable nowadays. Use it for point and signal wiring (with common return). It's stiff enough to stay where you put it, without needing lots of staples to hold it in place. But I use multistrand flexible wire for the droppers through the baseboard for track power, which is mainly figure-8, 10amp flex to minimize losses.
  gombul Station Master

Location: Canberra, Australian Capital Territory
I overlooked the fact that my 3 legged LEDs are actually common cathode. This updated diagram has the resistors moved onto anode inputs... Sorry for the confusion. Once I get to the bottom of all this I'll be writing up an article showing the way I ended up skinning the cat.

  miktrain Deputy Commissioner

Location: Adelaide SA
I overlooked the fact that my 3 legged LEDs are actually common cathode. This updated diagram has the resistors moved onto anode inputs... Sorry for the confusion. Once I get to the bottom of all this I'll be writing up an article showing the way I ended up skinning the cat.
gombul
The resistors can go either way as long as they are in series but as Aaron said separate resistors is best.
Please don't use any of your diagrams as you will regret it later, the LED wiring will work but the controllers will all be wired with common return and yes, all you who are about to say but it works, I know, but if you want to change to DCC later it can cause all sorts of big problems like failed decoders and weird shut-downs. Much better to do it right first time than rewire later.

Basic rules for easy wiring and trouble free running:
Run a separate power supply for each controller.
Run a separate power supply for points/CDU.
Run a separate power supply for lighting etc.

Join the negative of all supplies together, If using AC supplies (recommended) do this at the controller after the diode bridge
Double insulate all your blocks
Do not have any other common returns

Here is a better way to wire the switching for your LEDs and controllers
https://ozfreemo.com/members/index.php/Tony/Help-Files/controller-switching-with-panel-indicator
Unfortunately you need standard LEDs not the three colour that you have but they are so cheap it would only be a dollar for the lot. Please note well the orientation of the LEDs it is important and the diagram is right.

The really nice thing about this method is it is self diagnosing when a wire comes off.
Top LED not working, no power in.
Bottom LED not working, no earth.
Both LEDs on, control wire disconnected, or in your case track isolated.

If you want to stay away from relays then use the same set up but with 4PDT switches as Parkeston has said.

Tony

Edit on link to update to new location
  Aaron Minister for Railways

Location: University of Adelaide SA
The wiring in that diagram looks remarkably familiar. Reverse biased diode on the relay coil please...
  gombul Station Master

Location: Canberra, Australian Capital Territory
Ok, how about this (mostly my interpretation of Parkeston's post). Still keeping it simple (no relays) but separate power supply for LED and trains. By the way, my LEDs are common cathode. May as well use them if I can.

  Aaron Minister for Railways

Location: University of Adelaide SA
Stop common supplying the controllers!!
  miktrain Deputy Commissioner

Location: Adelaide SA
The wiring in that diagram looks remarkably familiar. Reverse biased diode on the relay coil please...
Aaron
Yeah, forgot that in my rush to upload it, now added.

You should recognise it, that is the way all well wired layouts are done, like our main layout and Paradigm but not "Lacklusture" which is why it has so many problems.

Tony
  miktrain Deputy Commissioner

Location: Adelaide SA
Ok, how about this (mostly my interpretation of Parkeston's post). Still keeping it simple (no relays) but separate power supply for LED and trains. By the way, my LEDs are common cathode. May as well use them if I can.
gombul

Ditto to Aaron, NO common supplies for the controllers, one per controller.

You also need to revise the output of your controller supplies, 12 volt is not enough, aim for around 15 to give you the ability to get ~12 to the track.

If you don't want to use relays, that is fine but remember all your track power has to go through the switches located at the control panel then to the layout so more heavier wire (more expensive) is needed, but if you use relays they can be located nearer the track and use lighter and less wire to control them.

Tony
  Parkeston Station Staff

Ok, how about this (mostly my interpretation of Parkeston's post). Still keeping it simple (no relays) but separate power supply for LED and trains. By the way, my LEDs are common cathode. May as well use them if I can.

gombul
Almost as I described.  The only change that you need to make to this diagram is to connect controller 2 to the "LEDs" power supply.

Each controller needs its own power supply, which is why the second power supply goes to the second controller.  But, because the LEDs are independent of the rest of the wiring, they can also be wired to the second power supply (or the first).

The LEDs won't add too much extra load to the power supply, so there's no need to power them separately.  You can if you want to but you don't need to.
  gombul Station Master

Location: Canberra, Australian Capital Territory
  Parkeston Station Staff

gombul
Spot on!

Depending on the actual voltage of the power supplies and the LED specifications you may need to adjust the value of the resistors a little bit, but the value I specified (720 ohm) should work in most cases.

Edit:  You will still need the reversing switch for the reversing loop, so that you don't get problems (i.e. smoke and sparks) when the train moves from the loop to the adjacent block, especially if the adjacent block is powered from the same controller.
  miktrain Deputy Commissioner

Location: Adelaide SA
Edit:  You will still need the reversing switch for the reversing loop, so that you don't get problems (i.e. smoke and sparks) when the train moves from the loop to the adjacent block, especially if the adjacent block is powered from the same controller.
Parkeston

There is no reversing section to wire, just wire the two loops in opposite directions and all will be fine. If you don't believe me redraw the loops and joining track, but not on top of each other, then mark one with left/right or +/- and then the other opposite, then go from one to the other via the joining track and it will become clear.

Tony
  gombul Station Master

Location: Canberra, Australian Capital Territory
Good eye Tony, I see what you mean.

As I can see, an issue remaining is prevention of one loco passing from one power source to another as it crosses blocks. This was the issue I was trying to mitigate by having only one power source for all track - the theory was that I would only have to manage polarity crossing in one spot (B3 to B6) and no crossing the steams (ghostbusters term).
  miktrain Deputy Commissioner

Location: Adelaide SA
Good eye Tony, I see what you mean.

As I can see, an issue remaining is prevention of one loco passing from one power source to another as it crosses blocks. This was the issue I was trying to mitigate by having only one power source for all track - the theory was that I would only have to manage polarity crossing in one spot (B3 to B6) and no crossing the steams (ghostbusters term).
gombul
There is no polarity problem but there always will be the possibility of controller swapping when there is more than one controller. That is an operator issue not a wiring one - look at the controller switch position before entering the block.

After another look at your plan unless your sidings are very long ,you could just power them from the local track ie red from yellow and tan from green, as you can not use them without first setting the point.

Tony
  gombul Station Master

Location: Canberra, Australian Capital Territory
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?
  Parkeston Station Staff

Edit:  You will still need the reversing switch for the reversing loop, so that you don't get problems (i.e. smoke and sparks) when the train moves from the loop to the adjacent block, especially if the adjacent block is powered from the same controller.

There is no reversing section to wire, just wire the two loops in opposite directions and all will be fine. If you don't believe me redraw the loops and joining track, but not on top of each other, then mark one with left/right or +/- and then the other opposite, then go from one to the other via the joining track and it will become clear.

Tony
miktrain
I'm sorry but I disagree.  The reversing loop (in pink) will need to have its polarity reversed before a train moves back out to the next block.

As the train runs from the previous section the polarity must match it as the loco(s) cross the join.  As the train runs around, the polarity will be wrong for the exit section, so the polarity must be reversed before the loco(s) cross the join leaving the loop.

If you don't do this the loco will cause a direct short circuit of the controller as it crosses the join.

In any case it will be very important to use controllers that have protection on their outputs.  If they don't then their life span may be quite short in this setup.
  Parkeston Station Staff

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?
gombul
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.
  gombul Station Master

Location: Canberra, Australian Capital Territory
I thought it did seem to make sense that if the blue section has voltage on outside and yellow section voltage on inside then where they meet (B3 to B6) the polarity is matched. I need to think it through carefully with regards to block control operation though.



As for the controllers I'm using, it's these kits from Ken Stapleton. He shares his circuit diagram on this page. 1.5 AMP PWM WALK-AROUND THROTTLE
  Aaron Minister for Railways

Location: University of Adelaide SA
There is no reversing section to wire, just wire the two loops in opposite directions and all will be fine. If you don't believe me redraw the loops and joining track, but not on top of each other, then mark one with left/right or +/- and then the other opposite, then go from one to the other via the joining track and it will become clear.

Tony
miktrain
I'm sorry but I disagree.  The reversing loop (in pink) will need to have its polarity reversed before a train moves back out to the next block.
"Parkeston"


THERE IS NO REVERSE LOOP!! And therefore, THERE IS NO REVERSE!!

All you are looking at is a glorifiedly long crossing between two tracks. Wire it accordingly, as per Tony's post.

The only reverse situation is if you cross between controllers that are reversed, but that is a problem no different to switching between two parallel tracks driven in opposite directions. The regulation forward/reverse switch and some operator vigilence will take care of the whole issue.
  Parkeston Station Staff

I thought it did seem to make sense that if the blue section has voltage on outside and yellow section voltage on inside then where they meet (B3 to B6) the polarity is matched. I need to think it through carefully with regards to block control operation though.


gombul
Sorry, you are correct.  If you wire it that way you will have no problems (other than block control).  Please accept my apologies.
  Parkeston Station Staff

There is no reversing section to wire, just wire the two loops in opposite directions and all will be fine. If you don't believe me redraw the loops and joining track, but not on top of each other, then mark one with left/right or +/- and then the other opposite, then go from one to the other via the joining track and it will become clear.

Tony
I'm sorry but I disagree.  The reversing loop (in pink) will need to have its polarity reversed before a train moves back out to the next block.


THERE IS NO REVERSE LOOP!! And therefore, THERE IS NO REVERSE!!

All you are looking at is a glorifiedly long crossing between two tracks. Wire it accordingly, as per Tony's post.

The only reverse situation is if you cross between controllers that are reversed, but that is a problem no different to switching between two parallel tracks driven in opposite directions. The regulation forward/reverse switch and some operator vigilence will take care of the whole issue.
Aaron
OK, now my brain is working.  Apologies to Tony who is correct.  There is indeed no reverse.

Must not post before finishing coffee...
  Parkeston Station Staff

As for the controllers I'm using, it's these kits from Ken Stapleton. He shares his circuit diagram on this page. 1.5 AMP PWM WALK-AROUND THROTTLE
gombul
OK, the first thing I note is that these controllers use AC power supplies.  You will need to get the power for your indicator LEDs from somewhere else.  You could build a little circuit with a bridge rectifier and smoothing capacitor, connected to one of the AC power supplies, for LED power or use another supply if you have one that you are using for something else on the layout.

With these controllers there should be no problems passing from a block controlled by one to the next block controlled by the other, providing they are both set for the same direction.  The loco may briefly accelerate a tiny bit as it does but the maximum voltage through the motor won't be any different so there's no danger to the motor.

I'm not sure what will happen if the controllers are set to opposite directions as the loco passes from one to the other.  The loco itself should just stop (and not be in danger) but each controller will be trying to power the other, so they will go into current limiting mode.  The heatsink will end up getting quite hot in this state, so one or both of the controllers would end up shutting down.

My guess is that they would probably be OK without any extra protection but the controllers would get quite hot to hold if the problem is not noticed quickly.  The lack of train movement may be a clue to a possible problem, though.
  gombul Station Master

Location: Canberra, Australian Capital Territory
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.

As an aside, I asked Ken about his AC supply. I hope he doesn't mind being quoted:


The controllers use AC so that a sample of the AC waveform can be used to generate the PWM wave shape that allows the controller to yield the performance that modellers love.
Ken Stapleton
  miktrain Deputy Commissioner

Location: Adelaide SA
OK, now my brain is working.  Apologies to Tony who is correct.  There is indeed no reverse.

Must not post before finishing coffee...
Parkeston

That's ok, sometimes we all have to step back and read what is written before posting. Glad you can understand it now.

Tony

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