Help!

[jimbob]

OK when it comes to electrics l like to keep it simple.

So as such my line is a normal out and back with no problems, or was. I have now installed a connection between the two running lines, a basic 2 point crossover between the running lines. This now, or will when l finish, cause a short as the polarity of the running lines will conflict i.e. red to black black to red. Now the simple soloution (to me) is to put a isolater in at the end of the section to form a break and let the point blades do the rest.

This all seems simple to me but is it?

Electical idiot requires help please.

[Baimor]

Hi Jimbob. Yes just isolate the crossover from the rest of your circuit mate. You can use isolating fishplates (plastic) then add some droppers wired to correct your polarity if that makes sense mate? A simple circuit tester or test lamp will help ensure you have all your polarities correct. Hope this helps. Regards. Mark

[Baimor]

Reading your post again Jimbob I think I may have misunderstood. Are you fitting a crossover or points? Mark

[jimbob]

Sorry its points, though l think the solution is still sound. Would a DPDT switch work as well ? (not that l know what one is though!).

[traingeekboy]

I tried to post something last night, but the internets were wonky. So onto attempt number 2.

The problem of course is that the outside rail will end up being an inside rail, and vice versa whenever you have loops, or wyes.

The underside detail of the DPDT switch shows how you have to run the wires to get a reverse polarity when you flip the switch.

-If you are doing DC or analog, you need two DPDT switches. You have to align the voltage so that the train enters the loop with proper polarity. While the train is in the loop, you reverse the polarity of the mainline.

-If you do DCC, you only need one. After a train enters the reverse section, you just flip the switch over and it doesn't even stutter.

Reverse loops can seem daunting, but it's really pretty simple electrical work.

[jimbob]

Thanks gents, that helped a lot. Shall have a go next week.

Am l right in thinking that one DPDT switch will only control break?

[Baimor]

Glad you got it sorted fella. To answer your last question yes on dc one DPDT will control break. On DCC one will control break and polarity reversal.

[chris]

To clarify. When you say "out and back" I assume you mean a line that loops around.

An "end to end" would mean there is no loop and a train would reach the far end and then have to reverse to return.

When you add points will you have something that works like this?

Edited April 23, 2016 by Guest

[chris]

traingeekboy said:

-If you are doing DC or analog, you need two DPDT switches. You have to align the voltage so that the train enters the loop with proper polarity. While the train is in the loop, you reverse the polarity of the mainline.

I've not come across the two switch system before. I like it. It's a rather elegant way of getting rid of the need to stop the train requirement.

However, I imagine it will be rather difficult to remember which way is forward and which is reverse if you can flip this on both the controller and the DPDT switch. And wouldn't it be a real headache if you have more than one DC Cab?

[jimbob]

I get it, l think! I assume that in practise the change over could be anywere on the line that contains the loop? Just thinking l would rather have the unit in the shed than in the open.

[traingeekboy]

I am guessing this is the kind of arrangement you are talking about for your layout.

Chris, I hope you do not mind if I borrowed your image in order to clarify things.

The best way to wire it is to have the place where the lines cross from either direction be isolated. Otherwise you would have to wire two blocks for reverse running, if you did the loops.

It really isn't that complicated when it comes to running the layout as logic behind the switches never changes.

If you have two switches, then you wire them so that normal loop running has both flipped upward, or both flipped downward.

Normal running

Mainline/Reversal Block

UP / UP

DOWN / DOWN

If you want to reverse direction the train enters the reversal and you switch the mainline to the opposite direction after your loco is cleared through that area. You end up looking like this.

After having passed through the reverser block

Mainline/Reversal Block

DOWN / UP

UP / DOWN

Once your train has returned to the mainline block, and you want to keep running the oval, you flip the reversal section to match the mainline switch, and return to a normal running set up.

Normal running

Mainline/Reversal Block

UP / UP

DOWN / DOWN

So all you have to do is look at your toggles and they will tell you what switch needs to be where. It all really is that easy.

Ok, another problem is that you are likely to want multiple trains running at once. In that case, you will need a reverser circuit for both locos, and a toggle to designate which loco is controlling the reverse section separately.

If you want separate control of two locos on the mainline, you have to do this kind of logic set up. If you do not do this, the problem will be that as one train is going through the reversal section, you will change the polarity on the mainline and cause another train to come to a screeching halt as it suddenly goes into reverse.

MAINLINE BLOCK SWITCHES

LOCO A LOCO B

Both rails are isolated for each block

with toggles to determine what cab controls it

LOCO A or LOCO B

REVERSER BLOCK SWITCHES

A toggle determines what cab controls the reverser block

LOCO A or LOCO B

And each cab has it's own reverser logic section

of two toggles each.

UP / UP UP / UP

DOWN / DOWN DOWN / DOWN

And yes, it's at this point when the concept of DCC begins to rear it's ugly head, because it makes all the power problems much simpler.

[jimbob]

Your all be glad to hear that l went to the Epsom & Ewell MRC show today and bought a book on DCC wireing etc. Spent this afternoon reading it and even an electrical idiot like me can understand it!

Thank you all for your help.

Books Digital Command Control by Ian Morton published by Ian Allan. Covers all the basics of DCC contol not just wireing, points, chip fitting and sound, plus programming locos, consists etc. Cover price was £20, bit steep for a tight wad like me but l think its going to be a good investment!

[chris]

Great idea buying a book. I borrowed a copy of that book when I first started with DCC and I found it helpful.

In the most part DCC is about wiring things up. All the electronics are done by the likes of Lenz, NCE and Digitrax and you just have to connect up the black wires and the red wires to the correct tracks and modules. Even chip fitting is simple enough on the vast majority of OO trains. The most difficult bit is often taking the loco apart to get to the insides.