passenger car block bridging

I kind of understand you mean that your passenger cars are bridging your blocks, but that shouldn't necessarily be a problem unless there is some kind of layout wiring/power issue.

How are you wired? Are you using toggle switch block control or are using a form of power district?  How many power supplies are you using and are they all in phase?  Are you running conventional or command?

Fred

From each pickup roller to the bulbs place a diode pointed toward the bulbs. On the next car point the 2 diodes away from the bulbs. Continue to alternate polarity between each car. Current will not pass through opposing diodes. Cars will receive the equivalent of about half of the voltage they did before. On an LED circuit conversion with a capacitor and constant voltage circuits this would make no difference, however light bulbs as is would be half as bright. Under command this is usually a +. If you use DCS also add a choke if adding a capacitor. 1n4001 diodes are OK very cheap to buy.

A second solution is to put a 1.35 amp resettable poly fuse between the rollers.

Here is a link to a poly fuse

www.allelectronics.com/make-a-...-0.65-1.3-AMP/1.html

A third solution is to use relays and make a transition block between the connecting blocks. That would eliminate roller jumping all together.

Depending on the track center gap and type,even one roller can bridge the block briefly but the first 2 methods will stop back feed through the connecting wires on the 2 rollers.

The relays with a transition block will eliminate roller jumping completely..

Dale H

Another solution would be to power the bulbs in each car with two small bridge rectifiers - each one getting it's AC from one of the truck's collectors, and chassis ground.  Connect the DC sides of the rectifiers in parallel and to the bulbs.

The avoids the possibility of a polarity imbalance and maintains brightness if desired.

avoids the possibility of a polarity imbalance

Just how is that?  The locomotive will still cross the same blocks as the passenger cars and it will still be affected by out of phase transformers.

Fred

1) You won't have to alternate the direction of diodes in each car or remember which cars have which diodes if you don't run the whole set(the polarity issue).

2) The lightweight wiring inside the passenger car is no longer carrying, potentially, the electrical load of an entire train, or whatever might be track powered(possibly 10-15 amps depending on the layout and equipment) in the adjacent block, if it's two pickups are bridging the two blocks(the current/amperage erratic/excessive speed issues).

3) The OP said nothing about a phasing problem - only the voltage differential passing a train from one block to another.  With long passenger cars and collectors on each truck, the train will behave quite erratically if the voltages don't nearly match.  The loco, with heavier wiring and closely spaced collectors, will likely only bridge the blocks once, briefly and quickly.  This is still a problem, especially with modern electronics, but nothing like when a whole passenger train continues it along it's whole length, or if you try to park a train with a passenger car bridging the blocks.

Unless I'm missing very basic just feed the lighting off of one pickup and eliminate the bridging all together.

Feeding off one pickup yields more flickering of the lights.  Personally, I prefer LED lighting, it only takes 30-40ma to light a passenger car brighter than it needs to be, so current draw is pretty much a non-issue.  Given the low current draw, a simple resistor between the rollers will solve the bridging issue.  Just feed the LED lighting from each roller with a 50 ohm series resistor.

Doh I knew that so why did I ask?  Thanks John.

Doh I knew that so why did I ask?  Thanks John.

Why just to make sure, right?

Originally Posted by wild mary:

Doh I knew that so why did I ask?  Thanks John.

Why just to make sure, right?

Yea but now I've got yet another black eye.

OK I'll ask; why alternate the diodes in each car? There is no connection between the cars except for the possible ground of the couplers. What would one car care about the polarity of the diodes in the other car?

Al

Al

Say we had 8 passenger cars with light bulbs and the didoes were always the same way. They could pull maybe 50 watts all off one half of the sine wave off the track transformer. Because of this there may be significant voltage drop off one side of the sine wave and a false triggering of the bell or whistle might occur. Also not sure how it would affect the transformer secondary,that would be a question for Dale Manquen. Now if we had 8 cars and 4 were one way and 4 the other ,the pull off the sine wave will be fairly balanced. With LED lighting,so little power is used that it probably would not matter.

As far as the lighting itself the polarity is not important.

The 2 bridge rectifier idea is interesting but would take a bit of time to wire.

Dale H

Someone mentioned relays. I once solved this problem the hard way with a circuit board in each car that worked on track power, and created 5v regulated DC that powered a 5v radio shack relay. The logic was: one pickup was the default, and if it saw power, the car lamps lighted, and the relay remained inactive. If the roller saw NO power, the relay would trip and default to the other pickup. If it saw power there, it tripped so fast, you saw no flicker as the relay switched over. Better still, no current passed from one roller to the other as they were now isolated. After making enough boards for an eight car train, however, I was pleased with the results, yet I questioned whether it was worth the labor to do another train. But it can be done.

Thanks Dale, did not think of that.

Al

Well, that's certainly the hard way, but interesting.

Wow that is some system!

What I meant was 2 relays and a transition block longer than the longest train run between the 2 power blocks being switched. The relays are positioned to activate at the outside of the transition block and work off the outside insulated rail. Only 2 short outside IR sections are needed. When the train approaches from one direction the DPDT relay coil is electrically latched with one of its own contacts through the NC contacts of the other relay SPDT. When the train leaves the transition block the relay is unlatched by the NC contacts of the other relay. The center contact of the unused set goes to the transition block center rail and the block power from the 2 power sources go to the NC and NO contacts. So the transition block can be powered by only one of the power sources which is switched as it enters and leaves the transition block. The system is bi directional. With this method the 2 power blocks can never be hooked together. Since the transition block is longer than the train there is no roller jumping.

Dale H

Boy, some of these solutions make me realize why I like command/control.

gunrunnerjohn.

BINGO!!! 

John running conventional IS command/control.  You're in command controlling everything.  For many of us guys that's the fun. 

You define it your way, and I'll define it mine.

The easiest way is obviously to use two bridge rectifiers.  That keeps everything isolated and there is no loss of brightness of the bulb. It is also probably the cheapest way.

People with command control with larger layouts run blocks with multi transformers and have the same issues with roller jumping. The blocks are connected via the 22 gauge wire connecting the rollers when the train bridges them thus 2 or more transformers are put in parallel. 20,30 and even 40 amps potential could be on the track when this occurs.

Derailments have also fried the pickup wires when the car is shorted between the center and outside rails even with modern transformers.Some time ago pictures of caboose wire meltdowns were posted.

The poly fuse recommended a long time ago by Dale Manquen makes sense and cost about $1 to add..

Dale H

Like I said, two diode bridges is the simplest solution.  No problem with derailments.

Dale, I've already agreed that the polyfuse is a good idea.  Most folks running command are using something like a MTH TIU or perhaps the TMCC Direct Lockon, these will trip immediately on an overcurrent and don't result in cooking the wires.  IMO a fast acting circuit breaker is mandatory, especially if you have any electronics involved.