Howdy,

Basic question: Can one part of a line be run by an MTH Z4000 and another little part of the same line be run with a Lionel CW80 (or CW40) without problems? Even though there is a break in the line using a standard block-type sectioin, my concern is putting the "Pure Wave" MTH Z4000 together with the "Chopped Wave" Lionel. While the current is not going from one to the other, it still seems like the common grounds will intermingle. Does this matter?
I experimented with this and I noticed that when the train crossed over from the Lionel CW40 section onto the MTH Z4000 section, the green light on the CW40 blinked (went off for a split second and then went back on)--is it trying to tell me something? When I tried this with a CW80 replacing the Z4000, there was no blink from the CW40 when the train crossed from one to the other.
Here's my reason for needing this: The main line (run by the Z4000) goes into another room where I can't see it. It then turns around and comes back. The problem is I have little space to make this turnaround and have to use 36-inch diameter curves. This means that if the train is high balling for most of the layout, it will need to slow down when it gets to this tight circle. I thought it would be possible to have a CW80 or 40 run the tight circle. The throttle on that would be reduced, and the train would slow down around the circle, avoiding a derailment. Then after it left the CW80/40 circle it would go back to high speed on the MTH Z4000 line. Any thoughts on this arrangement? Good, bad, harmless, problematic? Thanks.

I assume you're not running command control?..... Is there ever a time when one pick up roller is being powered by one source while the second pick up roller would be powered by the second source?..... Seems like that would be "interesting".....

Why not get a cheap Z 1000 or 750 and avoid any possible problem?
Just buy a controller only, and power it from the fixed 18v out of your big transformer. I find too many issues with CW80 chopped sine wave.

You are paralleling the 2 transformers via the wire between the pickup rollers. Not a good thing IMO. If you really have 2 do this I would isolate the 2 transformers with a couple of relays and an isolation block so they are never paralleled.

Dale H

If you don't have DCS yet, that what you need, then you can hit the brakes on the HiBall

OK, so everybody thinks this is a bad idea. OK, I'm on board. Yes, Mr Muffin, and Dale H, one roller is hitting the power from one transformer while the back roller is still on the other. Dave Allen, will take your suggestion under advisement, or Ope Express I probably don't have to go 140mph. Thanks all.

Any time the center roller bridges both blocks, if the voltages don't match exactly, you will get a short circuit. The circuit breaker on the CW80 is sensitive enough that it's probably sensing this.

Even if you match the RMS voltages between the two outputs, there will still be a voltage difference due to the differences in waveform. Thus, regardless of what you do, you're always going to have a short circuit.

I'd suggest wiring with block control, so that you can avoid having to transition between power districts powered by different power sources. This is good advice in general. I do this, and I power my layout using a pair of postwar ZWs.

Aside from this, there should be no issue mixing power supplies with different waveforms on a common ground.

Ben10ben, I've not had any problems with variable voltages when using a CW80 and CW40 for the two different lines, even though there are times when one roller would be on one power source, and the back roller on the other power source. I've had no problems, in the same way, with one track controlled by the left throttle fo the Z4000 and the other with the right throttle. So, do you mean the voltages have to be the same when there are different wave types involved? That aside, can you explain "wiring with block control?" I don't understand how it's physically possible to have one roller hit one block without the back roller still being on the previous. Thanks.

quote:

Originally posted by Rhaichen:
...I've not had any problems with variable voltages when using a CW80 and CW40 for the two different lines, even though there are times when one roller would be on one power source, and the back roller on the other power source...

This is actually OK with the CW/PowerMax/PowerMax Plus transformers, PowerMasters too. They will share the load, the higher set transformer taking the biggest hit by powering the whole train during the transition. The triacs don't mind being "backfed". This is something you shouldn't do with mismatched, non-phased, or traditional postwar transformers(especially different taps/posts/circuits on the same transformer) - there will be a short due to the potential difference.

quote:

Originally posted by Rhaichen:
...can you explain "wiring with block control?" I don't understand how it's physically possible to have one roller hit one block without the back roller still being on the previous. Thanks.

A transition section the length of your longest train between the two transformers is used, with a SPDT selector switch to pick which transformer of the two powers that section.

Start with the switch in position for the transformer running the train, when the train is completely on that track, flip the switch quickly to transfer to the next/other transformer, which is set to about the same speed level.

quote:

Originally posted by ADCX Rob:

quote:

Originally posted by Rhaichen:
...I've not had any problems with variable voltages when using a CW80 and CW40 for the two different lines, even though there are times when one roller would be on one power source, and the back roller on the other power source...

This is actually OK with the CW/PowerMax/PowerMax Plus transformers, PowerMasters too. They will share the load, the higher set transformer taking the biggest hit by powering the whole train during the transition. The triacs don't mind being "backfed". This is something you shouldn't do with mismatched, non-phased, or traditional postwar transformers(especially different taps/posts/circuits on the same transformer) - there will be a short due to the potential difference.

quote:

Originally posted by Rhaichen:
...can you explain "wiring with block control?" I don't understand how it's physically possible to have one roller hit one block without the back roller still being on the previous. Thanks.

A transition section the length of your longest train between the two transformers is used, with a SPDT selector switch to pick which transformer of the two powers that section.

Start with the switch in position for the transformer running the train, when the train is completely on that track, flip the switch quickly to transfer to the next/other transformer, which is set to about the same speed level.

Even if the transformers are properly phased,the pickup rollers in a car are connected by a 22 gauge wire. This may not be heavy enough to carry the current differential if the transformers are far apart in potential. As mentioned by others, transformers with unlike waves can never be phased. It is not just the sine wave shape,if the circuit is designed with capacitance the secondary could be delayed from the primary. With unlike modern transformers we are only guessing unless we have a schematic.

PW transformers if paralleled by the rollers with unlike potential by the pickup rollers can get sections of the secondary winding burnt,and this would not necessarily be breaker protected. To see this for yourself,put a PW ZW on a bench and plug it in. Connect a 22 gauge wire between A and B. Set A throttle at 6 volts and B throttle at 16 volts. Watch the wire fry while the breaker does not trip. This would be similar to the wire connecting the rollers in a passenger car or caboose jumping 2 blocks set at different potentials. This is also a bypass in the secondary winding,not recognized as a fault by the breaker. This may not damage modern transformers as they MAYBE do not back feed but the wire in the car can still fry.

Using the insulated rail method and 2 DPDT AC relays,you can automate the transition block so the transformers are not paralleled. As mentioned you can also throw a switch but it has to be done when the train is completely on the transition block.

Dale H

The best thing to do is use your cheaper/smaller power supplies for lighting, signels and accessaries. Buy a ZW or MTH large transformer for train power. If you intend to grow your trains this would be your best bet.

Tex

quote:

Using the insulated rail method and 2 DPDT AC relays,you can automate the transition block so the transformers are not paralleled. As mentioned you can also throw a switch but it has to be done when the train is completely on the transition block.

Three questions...

Are all (or most) relays "break-before-make" type so that the voltage mis-match (short) does not happen withing the relay switch?

Does the above mentioned method work for both directions on the transition block, or is another (or two) relays required to accomodate bi-directionality?

Is there a handy published reference describing this method for not paralling transformers?

Comment...

Three Rail Innovations has relay boards have have "power passing" modes for this -- but again, I don't know if it works for both directions.

quote:

Originally posted by Rail Reading:

quote:

Using the insulated rail method and 2 DPDT AC relays,you can automate the transition block so the transformers are not paralleled. As mentioned you can also throw a switch but it has to be done when the train is completely on the transition block.

Three questions...

Are all (or most) relays "break-before-make" type so that the voltage mis-match (short) does not happen withing the relay switch?

Does the above mentioned method work for both directions on the transition block, or is another (or two) relays required to accomodate bi-directionality?

Is there a handy published reference describing this method for not paralling transformers?

Comment...

Three Rail Innovations has relay boards have have "power passing" modes for this -- but again, I don't know if it works for both directions.

1) relays are designated by the amount of contacts and coil voltage. For contacts you can have SPST this would not be make-break,however SPDT,DPDT,3PDT,4PDT would be. The first number is the amount of circuits,the second is whether or not it make-breaks. To do the block isolation you would need a SPDT,and DPDT. There are no shorts in the contacts unless you wire them that way. The coil circuit is independent from the contacts unless you wire them in the coil circuit. Coil voltages vary. Common values are 5,6 12,24,28, volts DC and 24,110,and 220 VAC. 12VAC are not that common but exist. 12 and 24 volt relays are the most commonly used for model railroading. For track power contact ratings should be 10 amps or more.

2) the method would be bi directional. To make it I would use 2, 24 VAC DPDT relays. Make an isolation block as long as the longest train run,isolating the center rail. On both ends of the isolated section make a short outside insulated rail section,1 track long would be fine. Using the insulated rail method wire a relay on one side so it latches through its own NO contact and through the the NC contact of the other relay. So the train traveling one direction latches the relay and the other relay cancels the latch when it gets to the other side of the block. Using the other DPDT contact run the common to the isolated center rail,run transformer 1 hot to the NC contact and transformer 2 hot to the NO contact. When the train reaches the end of the block in either direction the whole train will be on the transition block and the transformers will switch the power on the transition block from one to the other according to train direction.

3) I do not know of any book but the circuit is commonly used and simple to make.

Dale H

Dale H wrote:

quote:

2) the method would be bi directional. To make it I would use 2, 24 VAC DPDT relays. Make an isolation block as long as the longest train run,isolating the center rail. On both ends of the isolated section make a short outside insulated rail section,1 track long would be fine. Using the insulated rail method wire a relay on one side so it latches through its own NO contact and through the the NC contact of the other relay. So the train traveling one direction latches the relay and the other relay cancels the latch when it gets to the other side of the block. Using the other DPDT contact run the common to the isolated center rail,run transformer 1 hot to the NC contact and transformer 2 hot to the NO contact. When the train reaches the end of the block in either direction the whole train will be on the transition block and the transformers will switch the power on the transition block from one to the other according to train direction.

I delayed so long in replying, as I was trying to sketch out the solution schematic described in the bolded section above.

I think that my difficulty came from assuming that I needed to latch through the NC connection of the other relay for both directions -- which seems impossible.

Am I correct to define a "default path" as the one that comes from side whose power goes through the NC connection on one half of a DPDT relay? The relay that is activated from the insulated 3rd on this side only disconnects the NC connection of the other relay -- ensuring that the relay with the track power through it reverts to the NC (default) power.

And to further verify: the important limitation is that a train from the default direction is short enough to clear the insulated 3rd rail on default side before its rollers bridge the power rail insulating pin on the other side?
.

Regarding the "make-before-break" discussion, I think my question/comment was mis-understood.

Rotary switches, which can be DPDT, seem more conerned with this, and specify their make-before-break versus break-before-make behavior. I assume, but don't know for sure, that most Toggle DPDT swiches are break-before-make.

My comment was that if a DPDT switch did exhibit make-before-break behavior, the different voltages would be shorted through the switch for the (short) period of time before the "break" happens.

I notice that of the solutions mentioned so far, something appears to have been overlooked:

quote:

The main line (run by the Z4000) goes into another room where I can't see it. It then turns around and comes back. The problem is I have little space to make this turnaround and have to use 36-inch diameter curves. This means that if the train is high balling for most of the layout, it will need to slow down when it gets to this tight circle.

(emphasis mine)

Is it possible to isolate the non-visible section and simply feed track power to it from the mainline through a bank of resistors? The only complication I can see from that is managing heat from the resistors. But assuming you can do that, this suggestion would slow the train down without the need to know when to flip a block switch (which is kind of difficult to do seeing as you can't see the train at the point it needs to slow down)

---PCJ

I would try the trick of wiring up a bridge rectifier 'weird'. Matt Jackson, I think, did a nice write up on it once.

I second the idea of using a resistor to step down the voltage to your isolated turn-around loop. I've done it on the downhill side of my fly-over track so I don't have to constantly watch to see when a train is starting downhill and reduce the throttle. That section of track is always a fixed, lower percentage of whatever the transformer is set at.

I've used fixed value ceramic resistors for this (can't remember the values offhand), variable ceramic resistors, and am presently using some of those old Lionel variable resistor controls sold when transformers only had fixed taps. You can usually find them at swap meets for less than $10.

I've also used this method to keep a "holding" current still flowing in the track controlled by my automatic stop station. It not only keeps the e-unit from cycling, but I think it gives the train a more realistic stop sequence; coasting to a stop rather than the abrupt stop you get with a complete current shut off.

FJ

quote:

Originally posted by Rail Reading:
Dale H wrote:

quote:

2) the method would be bi directional. To make it I would use 2, 24 VAC DPDT relays. Make an isolation block as long as the longest train run,isolating the center rail. On both ends of the isolated section make a short outside insulated rail section,1 track long would be fine. Using the insulated rail method wire a relay on one side so it latches through its own NO contact and through the the NC contact of the other relay. So the train traveling one direction latches the relay and the other relay cancels the latch when it gets to the other side of the block. Using the other DPDT contact run the common to the isolated center rail,run transformer 1 hot to the NC contact and transformer 2 hot to the NO contact. When the train reaches the end of the block in either direction the whole train will be on the transition block and the transformers will switch the power on the transition block from one to the other according to train direction.

I delayed so long in replying, as I was trying to sketch out the solution schematic described in the bolded section above.

I think that my difficulty came from assuming that I needed to latch through the NC connection of the other relay for both directions -- which seems impossible.

Am I correct to define a "default path" as the one that comes from side whose power goes through the NC connection on one half of a DPDT relay? The relay that is activated from the insulated 3rd on this side only disconnects the NC connection of the other relay -- ensuring that the relay with the track power through it reverts to the NC (default) power.

And to further verify: the important limitation is that a train from the default direction is short enough to clear the insulated 3rd rail on default side before its rollers bridge the power rail insulating pin on the other side?
.

Send me your address and I will snail mail you a sketch. The switching from one transformer to the other is done when the whole train is on the transition block or as it enters the transition block. Only one transformer can power the transition block. Latched Transformer A,unlatched transformer B,for example.

On a train going left (powered by transformer A) to right for example the front wheels latch the relay coil as it enters the transition block via the outside insulated rail. The transition block immediately is connected to transformer A. When the train reaches the end of the transition block the front wheels break the latch, connecting the transition block to transformer B (B powers the right side) Since the whole train is on the transition block no rollers are jumping the transformers.

A train going right to left. As the train enters the relay coil is unlatched (the front wheels break the latch if the relay coil is powered). The transition block is connected to transformer B. As the train reaches the end of the transition block,the relay latches (via the outside insulated rail) and transformer A is connected immediately to the transition block. Again since the whole train sits on the transition block 2 rollers can not connect both transformers. The system will work as long as the transition block is as long or longer than the train or the train does not accidently uncouple.

Dale H