Hi Bob (Nelson), and thanks again for sharing your wisdom
I'm still very interested in this concept, and just now circling back to it after a few years. I have some questions, but don't wish to burden others on the CTT Forum.
Could you please, please email me at: cando614 "at" aol dot com?
Thanks sincerely,
Ted Sowirka, Fort Worth, TX
I run two trains on the same track by putting a rectifier and filter capacitor in each locomotive, so that it is sensitive only to the half-cycles of one polarity. The two transformer outputs go through synchronous rectifiers (each comprising an SCR and a driver transistor) to connect each output to the track only during the half-cycle assigned to it.In the 1960's Lionel had slotcar sets that used rectifiers in the cars and in the controllers to allow two cars on the same track. There were still two lanes. The set came with a pair of switch tracks (one controlled by each racer) so the cars could switch lanes to block eachother.
This is great Bob, thank you so much!! I'm not an EE so I'll have to get help from someone who is. I'm reluctant to ask for more. But for others' benefit, and for the sake of more completely documenting this approach, some photos and/or schematic diagrams would be great. This is so good I think it deserves to be IN the magazine, or maybe a TCA / LCCA publication.
Folks operated tinplate trains for YEARS before the advent of TMCC. A lot has been written about cab control / block systems but they all involve much wiring. Frankly I'm surprised that this scheme wasn't more widely adopted, and isn't discussed in the literature more often. Thanks again for sharing!
The Wikipedia article on synchronous rectification, https://en.wikipedia.org/wiki/Active_rectification , emphasizes the efficiency advantage over a conventional rectifier diode realized by actively switching an AC supply voltage waveform on and off to a DC load in synchrony with the voltage polarity. For example, a synchronous rectifier may connect the AC supply voltage to the load when the supply voltage is positive and disconnect it when it is negative, so that the load receives only the positive half-cycles.
I use the same supply-to-load switching concept, but I switch two different AC supply voltages to a single track. I switch the first AC supply voltage to the track during the positive half-cycles and a second AC supply voltage to the same track during the negative half-cycles. Each of two locomotives on the track has a rectifier diode in series with its motor, so that the first locomotive responds only to the positive half-cycles of the track voltage, and the second locomotive responds only to the negative half-cycles.
The switches that I use are two identical silicon controlled rectifiers (SCRs, from the NTE5550-8 series). An SCR is a rectifier, but one that does not begin to conduct in the forward (anode-to-cathode) direction until current is put into a third terminal, the "gate" and stops conducting when the anode-to-cathode current goes to zero. The anode of first SCR connects to the first supply voltage. The cathode of the second SCR connects to the second supply voltage. The other anode and cathode are connected together and to the center rail of the track.
The first SCR is driven by a 2N3906 PNP transistor whose emitter connects to the first supply voltage and whose collector connects to the first SCR's gate, through a 1N4148 diode and a 100-ohm resistor in series. The second SCR is driven by a 2N3904 NPN transistor whose collector connects to the second supply voltage and whose emitter connects to the second SCR's gate, through a 1N4148 diode and a 100-ohm resistor in series.
A 3300-ohm resistor from the circuit common supplies each transistor's base with current, and a 1N4148 diode between the gate and the emitter protects against reverse voltage. Each complete switch circuit occupies about 1 cubic inch and is attached to the frame of one of my type-Z transformers, with the frame serving as a heat sink for the SCR.
If the rectifier in the locomotive is no more than a diode, there will be a 30-percent drop in the RMS voltage due to the blocking of half the half-cycles of the waveform of the supply voltage. On the other hand, if you wire an electrolytic capacitor in parallel with the locomotive's circuitry downstream of the rectifier diode, the RMS voltage may be increased by as much as 40 percent. In practice, I generally use a 5 millifarad capacitor, or twice or half that, according to the load I expect from that locomotive, to approximate the normal voltage. The exact capacitance is not critical.
The single-diode rectifier is fine if you have only two locomotives, or don't mind always pairing a positive locomotive with a negative one. But it is not hard to make the locomotive rectifier switchable: Just make up a bridge rectifier and put an SPST switch in series with any two consecutive diodes. When one switch is closed and the other open, the rectifier will allow the locomotive to respond to only one polarity. When both switches are closed, the locomotive will run on either polarity or, more important, on full-wave AC, almost as if it was not modified. And when both switches are open, the locomotive will not run.
One problem with the switched rectifier is that the circuitry downstream of the rectifier may not share a common with the locomotive frame. So you will need to move any items that are grounded to the frame to a separate common bus, for example, field windings of universal motors, E-unit frame, and lamp sockets.
I often use this synchronous-rectifier scheme even with a single train, by turning up the channel that I don't use for the locomotive to keep passenger-car and caboose lights on whatever the train speed. The lights lack rectifiers, so of course they respond to any voltage that is on the track.
If I have assumed too much famiarity with electronics, please say so, and I will go into more detail. I can also describe how to wire an air whistle to be controlled like a separate locomotive, or to be switched to operate with the normal whistle controller when running conventionally if anyone is interested.
Bob Nelson
Sorry to resurrect an old thread, but IMO this is a gem, and very timely since ERR / TMCC decoder boards are temporarily unavailable:
lionelsoni I run two trains on the same track by putting a rectifier and filter capacitor in each locomotive, so that it is sensitive only to the half-cycles of one polarity. The two transformer outputs go through synchronous rectifiers (each comprising an SCR and a driver transistor) to connect each output to the track only during the half-cycle assigned to it. This scheme prevents using the usual whistle relay. However, I have my whistles also wired with rectifiers. So, instead of two locomotives, I can control one locomotive's motor and one whistle tender's motor, allowing me to "quill" the whistle in a way impossible with a whistle relay. All my whistle-motor rectifiers respond to positive half-wave voltage, since I can always assign the locomotive to the other polarity. Each tender can be switched to normal relay operation if desired. My locomotive rectifiers use a more complicated switchable bridge scheme than you would need if you limit yourself to a permanent assignment of polarity to your locomotives. I do this so that each locomotive can be assigned to either polarity, as needed, or to full-wave operation, which is handy if running on someone else's layout. It is also possible to replace the synchronous rectifiers at the transformer with simple diodes if you are willing to control speed with two rheostats fed from a single transformer output.
I run two trains on the same track by putting a rectifier and filter capacitor in each locomotive, so that it is sensitive only to the half-cycles of one polarity. The two transformer outputs go through synchronous rectifiers (each comprising an SCR and a driver transistor) to connect each output to the track only during the half-cycle assigned to it.
This scheme prevents using the usual whistle relay. However, I have my whistles also wired with rectifiers. So, instead of two locomotives, I can control one locomotive's motor and one whistle tender's motor, allowing me to "quill" the whistle in a way impossible with a whistle relay. All my whistle-motor rectifiers respond to positive half-wave voltage, since I can always assign the locomotive to the other polarity. Each tender can be switched to normal relay operation if desired.
My locomotive rectifiers use a more complicated switchable bridge scheme than you would need if you limit yourself to a permanent assignment of polarity to your locomotives. I do this so that each locomotive can be assigned to either polarity, as needed, or to full-wave operation, which is handy if running on someone else's layout.
It is also possible to replace the synchronous rectifiers at the transformer with simple diodes if you are willing to control speed with two rheostats fed from a single transformer output.
Bob, has your scheme ever been documented in a feature article, perhaps in CTT magazine, TCA or LCCA publications, etc.?? I might be VERY interested in doing the same type of thing, but I need more documentation to do so.
I'm not familiar with synchronous rectifiers, but I can see the advantages of this approach vs. using two rheostats. If you don't mind me asking, what make and model of rectifier(s) are you using? Do you need two rectifiers, or just one? Also, could you please provide a wiring diagram, or describe the "switchable bridge" scheme inside the locomotive? Are you controlling current in just the armature, or both the armature and field?? Sorry for all the questions!
I'm not sure if I will implement your whistle/horn control. But I can definitely appreciate a bullet-proof, reliable way to independently control two trains on the same track. Especially postwar / MPC vintage locos, which I'm very nostalgic about, but they would not easily convert to direct radio control.
Look forward to learning the specifics necessary to recreate this scheme at home! -Ted
Perhaps simpler (?) would be to lock in forward only, for both engines. Then separate at points opposite each other on the tracks. Because virtually all engines run at different speeds at the same transformer setting, one will catch up with the other. Sometimes quickly, sometimes slowly. One way to slow down this problem is to add more cars or loads in cars on the faster train, thus slowing its speed to almost (perhaps exactly) the same as the slower train. In addition to this you can make a passing siding with 2 switches/turnouts and then make the siding a seperate block and park one of the trains there by killing the power with a throw switch, until the other has passed.
Has anyone ever used "CTI" on American flyer two-rail conventional layout? They say:
CTI system is completely "gauge independent." It is currently in use with all model railroad gauges from Z through G".
I need to see the "men at work" I say!
How about a video?
AZ-Flyer
“Tell me and I’ll forget; show me and I may remember; involve me and I’ll understand.”
AZ-Flyer@American Flyer Cabinet-top Layout (5'x16'): http://az-flyer.blogspot.com/
http://www.cti-electronics.com/whatscti.htm
Here is a possiblity.
Bob.M This is what I had in mind for a multi loop layout. It is from the Lionel TrainMaster Owner's Manual:
This is what I had in mind for a multi loop layout. It is from the Lionel TrainMaster Owner's Manual:
The reason this diagram works, and does not carry the same precautions as the KW & ZW require, is that the electronic circuitry of the PowerMasters does not allow for fault currents, the throttle set higher takes the load off the lower throttle, the triacs don't mind being back-fed with the higher voltage.
Rob
lionelsoni .... But, when you connect any of the A, B, C, or D terminals of a ZW together, you create a circuit that can supply a very large current that passes through no circuit breaker. ...
.... But, when you connect any of the A, B, C, or D terminals of a ZW together, you create a circuit that can supply a very large current that passes through no circuit breaker. ...
Good point. I had not thought of that.
I don't know what's inside a "Power Master". But, when you connect any of the A, B, C, or D terminals of a ZW together, you create a circuit that can supply a very large current that passes through no circuit breaker. The Lionel warning is an understatement--the voltages need to be exactly equal. If they are very close, the current may be limited by the wire resistance and, more likely, the resistance of the carbon rollers. It is also brief, as the train moves over the gap, which is why you can get away with it if you're careful. You could also get away with having no circuit breakers in your house wiring--if you're careful.
Yes, the breaker is (should be) rated at 15 amperes.
One way to make a ZW safer is to add individual breakers on the four outputs. These can be rated at 5 to 10 amperes if you like, since no one train is likely to draw more current than that. This is a good idea even if you are using a proper block system, since even then it is possible to get the switches wrong and connect two outputs together over a gap. But adding these breakers does nothing to reduce the arcing and voltage-spike production.
There is a similar layout in the ZW manual.
Quoting the ZW manual, dated January 1954:
"When crossing from one loop to another it is important that the voltages supplied to the inner and the outer loops are approximately equal."
The circuit breaker in the ZW serves the common lead. I had to repair mine in 2003, as it was tripping at 4 to 5 amps. I think normal is 15 amps.
I have quoted Lionel's fine-print disclaimer on the KW's service manual; but here it is again:
"Note that the circuit breaker does not protect binding post combinations A-B, B-D and C-U."
As far as I know, that is the only time Lionel acknowledged the problem; but they used the same single-circuit-breaker arrangement in all their multiple-train transformers.
The safety situation is not so bad when you use separate transformers and wiring heavy enough to handle the current before one of the circuit breakers trips. But there are still possible risks from arcing and from voltage spikes generated by the transformers' stray inductance.
Bob.M lionelsoni: If you go this way, do not run the train from a track powered by one transformer output to a track powered by another transformer output, especially if the two outputs come from the same transformer. .... I have done this for decades, just approximately matching the voltages prior to crossover...
lionelsoni: If you go this way, do not run the train from a track powered by one transformer output to a track powered by another transformer output, especially if the two outputs come from the same transformer. ....
If you go this way, do not run the train from a track powered by one transformer output to a track powered by another transformer output, especially if the two outputs come from the same transformer. ....
I have done this for decades, just approximately matching the voltages prior to crossover...
You lucked out.
There is ZERO overload protection among differently set outputs of Lionel's better transformers.
If you are using a newer ZW PowerHouse controller or PowerMasters, the risk is actually minimized - the back-fed triacs don't give a hoot.
lionelsoni If you go this way, do not run the train from a track powered by one transformer output to a track powered by another transformer output, especially if the two outputs come from the same transformer. ....
If one is using a rugged postwar transformer, such as the ZW, and not an electronic version, what is the problem with letting the engine cross over the gap between the two sections? I have done this for decades, just approximately matching the voltages prior to crossover.
And why should it matter whether it is 2 transformers or one? These have bimetallic circuit interrupters which would trip if anything was grossly wrong.
If you go this way, do not run the train from a track powered by one transformer output to a track powered by another transformer output, especially if the two outputs come from the same transformer. Instead, use a single-pole-double-throw-center-off (SPDT-CO) switch for each track, to assign the two tracks to the same transformer for the interchange. Note that using two transformers in this way also allows you to have as many blocks as you want to buy switches for on each loop and allows you to stop a train in one block while running two others in other blocks.
I realize you said "on the same track", but don't overlook the simpler solutions.
Since you are considering buying some O-36 track,the simplest way to run 2 engines is to have 2 separate ovals, with the O-27 being the inside loop. Attach one transformer to each loop.
You could add a couple of switches to connect the 2 ovals, using an insulated pin to keep the center rails isolated between inside and outside loop. Maybe add a siding to park one engine temporarily.
Optionally add a CAB-1 controller (12868) and 2 TMCC Powermasters (24130) so you can walk around the layout running the 2 engines. This works with conventional, postwar engines.
If you ever buy a TMCC engine, you need to add a TMCC Command Base (6_12911). You will still be able to operate the conventional engines. Since I have only 1 TMCC engine, about the only advantage is the ability to use the uncouple function anywhere on the layout.
Personally, I rarely run 2 engines at the same time, as I am too worried that one will fall off the track if I am not paying close attention to it.
sciencemonter- Welcome to trains.com!
Darren (BLHS & CRRM Lifetime Member)
Delaware and Hudson Virtual Museum (DHVM), Railroad Adventures (RRAdventures)
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For kicks and grins, I made a layout where the two outside rails were isolated from each other for two circuits, and the center rail was ground. I then painted the wheels on opposite sides of two engines with insulating paint. It worked, but the paint wore off pretty fast.
It was quite a while ago, so I don't really remember how well it worked...but I would guess it didn't work great or I'd still be using it...
What I have posted, however inconvenient, are all schemes to provide completely independent control without TMCC (nor DCS nor DCC), as requested. There is another one, Lionel's "Magic Electrol", that lets you control direction independently, but not speed: You rewire the whistle relay of one locomotive to operate the E-unit rather than the whistle.
Well, overhead catenary is a LOT of work to setup and maintain!
I should mention another, much older method that amply predates TMCC. That is to use means other than a center rail to get current to the locomotives.
In the early days of model railroading, it was common to use an outside third rail, like that used on some prototype railroads. Lionel sold outside-third-rail shoes for applying to their locomotives for this purpose. This was done even for steam locomotives, whose pickup shoes were supposed to be unobtrusive.
It is also practical to run models of electric locomotives, like the GG1 and EP5, from overhead wire. In fact, you will find that these locomotives have solder lugs under their pantographs for just that purpose.
By using one of these two techniques along with the usual center rail, you can run two trains independently, or three trains using both techniques together.
I find it a lot easier to use TMCC to run multiple locomotives on a single track.
KRM...Block systems will work but you will need to lock the engines in the direction you want them running in...
Not if you use rheostats to maintain E-unit position. With newer electronic reverse units, the bleed voltage can be very low, but you want it to be adjustable to give better visual operation(whether mechanical or electronic).
Same here, adding a second transformer for cab B would eliminate the need to lock out the E unit's. You can also use delay off relay's to make control rail shorter.My friend did it on a 10 x 8 layout. You still need to tweak it to work the you want it to operate, and this can get very complex.I went to TMCC to keep it simple and easy to trouble shoot, and you can run as many trains as space allow's.
Mike
I agree Block systems will work but you will need to lock the engines in the direction you want them running in. And they work better on larger layouts
Kev
Joined 1-21-2011 TCA 13-68614
Kev, From The North Bluff Above Marseilles IL.
You can use an automatic block control system that has been used by Lionel operators for over 70 years:
No, you cannot control conventional locos independent of each other, unless there is some kind of electronic upgrade kit that would allow you to do that, however I am not aware that there is.
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