I can't believe that they would create an uncoupling track that requires 10-12 volt, and then run all their LC and LC+ trains at 18V. It either forces people to re-wire a section of their FT to handle the uncoupling track, or - as I imagine is more likely - set up on track power and potentially start a fire. [/rant over]
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To uncouple rolling stock only requires that you power an uncoupling coil for a fraction of a second, during which time negligible heat is developed, regardless of whether it is 12V or 18V. In fact, you will get more reliable operation of many magnetically activated couplers or operating boxcars at the higher voltage. All my magnetic uncouplers are wired with 18V fixed voltage and I have never had an issue.
On the other hand, if you're determined to hold the button down until you receive a meltdown, it won't matter whether it is 10V-12V or 18V, you'll burn or melt something.
@GregR that's good to know. It looks like it's just one connection (the magnetic power is isolated from the track, so all you need is to disconnect one wire and run it to the other transformer) but still, it's an odd "design feature". Maybe much ado about nothing on my part though.
I have a related question.
Can you use dc power pack that comes with the set if you have an uncoupling section? I purchased a LC set and a fastrack uncoupling section for the grandkids for under their tree. They like my dump and mail cars. So I also sent them a mail car. After sending them these items, today it struck me. Do I need to get them a ac power source? I run all Ac under my tree partly because I run three loops.
Mark W
@MWasko posted:I have a related question.
Can you use dc power pack that comes with the set if you have an uncoupling section? I purchased a LC set and a fastrack uncoupling section for the grandkids for under their tree. They like my dump and mail cars. So I also sent them a mail car. After sending them these items, today it struck me. Do I need to get them a ac power source? I run all Ac under my tree partly because I run three loops.Mark W
No - DC will melt the track. See:
ALL Operating Track sections have operated best with auxiliary "hot" power since the dawn of the five rail sections in the pre-WWII era. On my O Gauge tubular layout, ALL of my Operating Track sections are wired this way. That way , they operate best whether I'm operating in the Command 18v environment, or with Conventional 0-18v.
Jon 
I have a separate transformer, set at about 12V to run all my Fastrack uncoupler tracks. It is an easy connection under the fastrack, as it is designed to run off track power or a separate transformer. You simply change where the wire is connected and you have isolated the uncoupler from the track power.
I lowered the voltage to reduce the noise, and to produce less heat when operating the uncoupler. Be warned that the pushbutton that comes with the Lionel fastrack uncloupler sometimes sticks, which will melt your track in about 30 seconds ($25 gone up in smoke). I added an LED to all my fastrack uncoupler track sections so that I could see when the uncoupler is activated. I also found that connecting the fastrack to DCS AIU channels 1 or 2 would also sometimes stick and melt the uncoupler. Learned all this the hard way. Now I run my trains instead of sniffing for a burning uncoupler magnet melting my fastrack.
I ended up replacing almost every single Lionel push button, with a more reliable push button purchased at an electronics store.
You could also install a PTC resettable fuse inline with the switched power input to the uncoupling coil to protect it from overheating. The Bourns MF-R050 has the recommended specs.
I ran into that problem last year with the LC set my daughter and her husband got for my grandson. The uncoupler track wouldn't activate enough to uncouple the cars.
The problem was the under powered wall wart they are including with the sets now. I substituted a used laptop power supply for the anemic one and the uncoupler and everything else works great.
https://ogrforum.com/...4#154730474318827774
John
@SteveH posted:You could also install a PTC resettable fuse inline with the switched power input to the uncoupling coil to protect it from overheating. The Bourns MF-R050 has the recommended specs.
Bingo. I don't have FasTrack, but for MTH RealTrax the user chooses if an operating track (switch, uncoupler, whatever) is powered by track voltage or separate accessory voltage.
In the RealTrax turnout, there is a metal jumper/strap which connects the solenoids to track voltage. By inserting a PTC you can protect the solenoid from overheating if track voltage happens to be DC or if the turnout gets stuck continuously applying power (AC or DC) to the coil.
Since PTC's are less than $1, this is one alternative to wiring up 2 transformers to a "simple" Xmas-tree or similar layout.
Just be aware that the PTC isn't a be all end all solution here for DC operation. When used with the LC 18VDC power supplies, that 5-6 ohm uncoupler coil will be drawing close 4 amps which touches or exceeds the capabilities of the LC power supply. That is more than the 1.2 or so amps it would draw on AC. Even further, that PTC, when activated, operates by heating up and increasing resistance and therefore decreasing current. That means it is going to get hot hot hot while saving the coil. The PTC recommended is tied to the AC characteristics of the coil, not DC.
Stan, thank you for the affirmation. This reminds me of a thread from earlier in the year: Fastrack Operating Track Wiring and Issues where the solution was to install the MF-R050 inline between the control rail and the coil.
For the 5" FasTrack Uncoupler here's what the PTC connections could look like if using Track power. Note where the red arrow is pointing the wire would need to be de-soldered from the U- shaped terminal and one of the PTC leads would connect in its place. That de-soldered wire would connect to the other PTC lead as shown.
If providing Aux Power and Ground here is an example of the power connections. The PTC could still be inserted in-line with the coil wire as shown above.
I'm going to say that a lower PTC will trip faster (sub second) and thus provide some protection to the coil, but in doing so, be useless for providing expected operation from a DC power source. I also would think that the smaller PTC will generate more heat. Thus, I simply just don't recommend DC operation - period.
I see the one offshoot of this discussion as coming up with practical ways to operate the uncoupler with DC...not to debate AC vs. DC which has been covered in many OGR threads with links provided earlier.
In this OGR thread, @PLCProf provides the key electrical parameters for the FasTrack uncoupler coil... 5 Ohms and 10 mH. The math is tedious and is explained in the thread, but basically the coil "looks like" 5 Ohms to DC and 9 Ohms to AC. Amps = Volts / Ohms. For 18V DC, current is ~3.6 Amps. For 12V AC which is apparently the max recommended by instructions, current is ~1.3 Amps.
So the MF-R050 will nominally trip in 10-20 seconds with 12V AC applied, and just under 1 second with 18V DC applied. Yes, these are nominal curves and there are other factors in play but the idea is to see if we're even in the ballpark. I think we are.
Having the PTC trip EVERY time you fire the uncoupler using 18V DC seems a bit screwy. Instead I'd choose one of the higher current devices to trip in, say, 3-4 seconds (blue circle on the family of curves). In other words, assume you typically fire the coil in, say, 1 second so during "normal" operation the PTC never trips. Of course, there are going to be the guys that say they prefer to hold down the uncoupler button for many seconds as they slowly roll a coupler over the coil. That is, it can be a hassle to position a coupler directly over the coil sometimes requiring going back and forth. So that is a consideration. On the other hand, since coil pulling force is proportional to the current in the coil, the 18V DC powered coil, when active, pulls with at least twice the force of the 12V AC coil so this might give some wiggle room to having to exactly position the coupler over the coil!
Finally, it helps to step back and reflect on what's going on here. This all comes down to heat management. With 12V AC applied, the coil dissipates 7 Watts. With 18V DC applied, the coil dissipates a whopping 65 Watts! That's about 10 times more power which of course is why it trips about 10 times faster since the PTC is effectively a thermal sensor.
It has been documented in other threads that you need one of the higher power (Watts) DC power packs to operate the FasTrack uncoupler. That stands to reason if you are pulling 65 Watts (3.6 Amps) when you press the uncouple button!
But here's another thought. For those applications where a second AC-output transformer is used just for the uncoupler, why not make that second power pack a DC-output wall wart. Technology is such that DC-output bricks in the voltage and power ranges under discussion are more compact, lighter, and less expensive that AC-output bricks. A picture I like to show which I've posted many times before:
A 90 Watt universal laptop charger with selectable DC output voltage (12V, 15V, 18V, more) which goes for about $10 could be used for the uncoupler power. It could be set for, say, 12V DC output so the coil current would be about 2.4 Amps which would cut power to less than half yet still have more pulling power that the 12V AC coil. And all the "extra" 12V DC power could power up a bunch of 12V LED lighting strips to spruce up the layout!
But wait. There's more. 
For $1-2 you can get a DC-to-DC converter module that can convert the 18V DC track voltage down to, say, 8V DC. So this would supply about 1.6 Amps DC into the coil...or about 13 Watts rather than 65 Watts if directly using the 18V DC track voltage. There is some conversion loss so you'd need say 18 Watts of 18V DC power to generate the 13 Watts of 8V DC power. But the point here is this would allow you to use one of the lower-powered Lionel 18V DC power pack which are apparently what comes with their train sets rather than upgrading to the higher power 72 Watt Lionel DC power pack which is somewhat spendy IMHO. That is, in reading some of the other OGR threads, you need this 72 Watt version to reliably fire the FasTrack uncoupler.
Thank you for all the great responses.
As they are +1,000mi away from me, any rewiring, soldering, or dedicated power supply for the uncoupler would require me to be there. So, the immediate solution looks like getting them an AC source to run the train and uncoupler or wait for me to visit.
Your responses bring up another question. I have used a secondary AC power source for accessories and uncoupler when my track power is AC (z-1000). But, can you have the track power DC (LC wall wort) and the uncoupler using AC power wired like you wire the section when you are using two AC sources?
@MWasko posted:I have used a secondary AC power source for accessories and uncoupler when my track power is AC (z-1000). But, can you have the track power DC (LC wall wort) and the uncoupler using AC power wired like you wire the section when you are using two AC sources?
Yes. In the picture the Orange (AC Hot) and Gray (AC Common/ground) wires from an AC transformer could be connected as shown to the Aux Power and Aux Ground input connections on the Uncoupler.
You can use an AC AUX power source for the uncoupler magnet and remain DC on the track, but since you suggest adding a Z1000 in the mix at 100 Watts of AC power, that is more than sufficient to cover whatever the LC Wall Wart does AND the uncoupler track AND leave a little room for further expansion allowing for decommissioning of the cost reduced and less capable DC wall wart. This expands the freedom of the setup to run just about everything 3 rail O gauge ever made from items over a century ago to items hot off shelf without worry.
@bmoran4 Thank you for your explanation. I did some further reading on PTCs: composition, electrical characteristics, and operation and what you've said about them makes sense to me now. What I didn't understand initially was how:
@stan2004 Thank you for your suggestions on how one could possibly use lower voltage DC power sources for the Uncoupler. I especially appreciate the link to the Uncoupler rewind thread and the discussion on how reactance in an AC circuit decreases current draw by the coil and lack of inductance increases it with DC. There was a lot of great information discussed/presented there.
Again, thank you both for your contributions to this topic and the Forum at large.
@MWasko posted:... I have used a secondary AC power source for accessories and uncoupler when my track power is AC (z-1000). But, can you have the track power DC (LC wall wort) and the uncoupler using AC power wired like you wire the section when you are using two AC sources?
In this recent OGR thread involving the Lionel Gateman accessory, the instructions (dated 2013) for the Gateman explicitly notes the situation of 18V DC track power from the LC power pack but requiring a separate AC power source for the accessory:
What's curious are the warnings for the Fastrack uncoupler apparently dated 2008.
There is no warning against using 18V DC...or more generally no warning about using DC at all. There is a warning not to operate for more than 10 seconds. And a curious but un-explained (why) warning NOT to use the accessory AC from a CW-80 transformer. Interesting. I thought the CW-80 could be programmed to set the Accessory AC voltage to what you want. 
Reflecting on the original post of this thread, I suspect it's on someone's to-do list to update the Fastrack Uncoupler instructions to warn against using 18V DC track power?
My experience with uncoupling tracks is that the current draw is way too much to add to your track power, so separate power supplies are pretty mandatory.
@gunrunnerjohn posted:My experience with uncoupling tracks is that the current draw is way too much to add to your track power, so separate power supplies are pretty mandatory.
On larger setups, I fully agree with the desire to use auxiliary power. However, on a basic loop of track with a CW-80 and uncoupler, the train is stopped in neutral when the ucoupler is operated, so there isn't much of anything else drawing current so it isn't absolutely necessary. As calculated above, the current draw is shy of 2 amps, about the equivalent of a typical locomotive (which is now inactive), and so you are just swapping one current draw for another in roughly equivalent amounts.
My experience is 99% with command control, and I find the transients introduced by the coupler coil is detrimental to operation and health of the locomotive electronics.
@SteveH, see this thread for the CW-80 warning explanation: https://ogrforum.com/...20#28742126432605020
It boils down to an oversight where the common ground terminals were mixed up and so use of the accessory terminals would produce a short.
@gunrunnerjohn posted:My experience is 99% with command control, and I find the transients introduced by the coupler coil is detrimental to operation and health of the locomotive electronics.
Well, we all preach about TVS diodes for that. And it isn't just the uncoupler coil that can generate transients.
Geez, spend $30 on an accessory transformer for operating - uncoupling tracks, switch power, lights - use whatever voltage works best problem solved. It sure isn’t as complicated as all that.
I can see your point if you only have one uncoupling track to operate, why spend another $30, but if you’re going to expand and include any of the things I mentioned going forward it might be worth it cuz they all work a lot better on a separate power source.
@bmoran4 posted:Well, we all preach about TVS diodes for that. And it isn't just the uncoupler coil that can generate transients.
I actually have some knowledge of transients and the use of TVS devices as well as other remediation measures. 
However, as I said, the uncoupling track actually would upset the running of a TMCC/Legacy engine elsewhere on the track.
Again, IMO, it's pretty mandatory to have separate power for the uncoupling track.
@bmoran4 posted:@SteveH, see this thread for the CW-80 warning explanation: https://ogrforum.com/...20#28742126432605020
It boils down to an oversight where the common ground terminals were mixed up and so use of the accessory terminals would produce a short.
It was me that wondered about this. Thanks for the link.
Apparently there's a new version of the CW-80 is coming out hopefully not adding to the confusion!
@gunrunnerjohn posted:I actually have some knowledge of transients and the use of TVS devices as well as other remediation measures.
Again, IMO, it's pretty mandatory to have separate power for the uncoupling track.
You are changing the premise away from the simple R2R loop "exception" that I am suggesting may be made. When you throw in more complexities and include TMCC/Legacy, I fully agree with the use of accessory power - no argument from me there. And even on a small R2R loop, if they already have the means for accessory power, by all means they should use it for the uncoupler!
@stan2004 posted:It was me that wondered about this. Thanks for the link.
Apparently there's a new version of the CW-80 is coming out hopefully not adding to the confusion!
This was addressed a decade or so ago. Any CW-80s revision G or later (G prefix on the date code), or with a QC50-OK label are wired up correctly.
@gunrunnerjohn posted:I actually have some knowledge of transients and the use of TVS devices as well as other remediation measures.
Again, IMO, it's pretty mandatory to have separate power for the uncoupling track.
I guess that's why they call them "starter" sets...to get you started. I just have an issue with having to immediately upgrade to two transformers, or a transformer with separate track and accessory outputs when you add a "simple" accessory.
As for the transients, better safe-than-sorry of course considering TVS components are inexpensive. But recall the marathon discussions about TIU failures from track transients. They tended to occur in layouts with lots of train action/power. It was the intermittent shorts (e.g., engine rolling over a switch) and loss of track power (e.g., dirty wheels/track) with Amps flowing in the track that caused "di/dt" transients thru the inductance of the track.
I’m sure one uncoupling track will work fine off track power for a quick jolt at 18 volts. I will caution that the plastic buttons can stick and if not careful you will find the pungent aroma of burnt plastic unappealing and the buying of a new uncoupling track more so.
@SteveH posted:...@stan2004 Thank you for your suggestions on how one could possibly use lower voltage DC power sources for the Uncoupler. I especially appreciate the link to the Uncoupler rewind thread and the discussion on how reactance in an AC circuit decreases current draw by the coil and lack of inductance increases it with DC.
...
I realize the eyes glaze over when the techno-babble of resistance vs. impedance/reactance comes up. But on that side-track, my curiosity about the CW-80 accessory voltage "warning" stemmed from how the CW-80 generates the accessory voltage by chopping the "pure" sinewave from the transformer.
That is, 12V AC from a CW-80 Accessory Output is 60 Hz but a "messy" 60 Hz. So when the impedance of the uncoupler coil is calculated to be ~9 Ohms, that assumes a pure 60 Hz voltage driving it. The impedance of the uncoupler coil driven by a chopped 60 Hz voltage will be higher because there are higher frequency so-called harmonic components. Plus, the chopped waveform will have peak voltages based on the CW-80 pure sinewave "starting" voltage (e.g., 18V AC) so the peak currents into the coil will be larger for the "same" accessory voltage. The math is very tedious to do a proper analysis and I figure will be a small effect. But as explained, it was a wiring issue in some early versions of the CW-80 that is the issue so I was off track.
Again, I figure OGR is a discussion forum for the exchange of ideas.
@William 1 posted:I’m sure one uncoupling track will work fine off track power for a quick jolt at 18 volts. I will caution that the plastic buttons can stick and if not careful you will find the pungent aroma of burnt plastic unappealing and the buying of a new uncoupling track more so.
Needless to say, (but I'll say it anyway ) a stuck button at the prescribed 10-12V AC will also provide the aromatherapy and wallet-thinning experience.
Like adding TVS protection devices, perhaps adding inexpensive PTC devices to coil-based accessories would be a good rainy-day project. In the long history of coil-based accessories, inexpensive self-resetting protection components like the PTC are relative newcomers.
@stan2004 Thank you for the reply. I like details, "techno-bable" and math. These are some of the ways those of us who are interested learn more about electronics, science, mechanics, and craft. Discussion of these things leads to greater understanding and sometimes, if we're lucky, either a breakthrough or an eureka moment. Please keep it coming. For those whose eyes are starting to glaze, they have the option of skipping past it. 
Yes, but sometimes these discussions roam far off the original topic, which is not a bad thing for those interested but if the guy wants a simple answer to a very basic question…
My suggestion is to operate your one uncoupling track off track power at 18 volts. Be careful with the push buttons that might stick. If you want to expand to more uncoupling/operating tracks, switches, lights, operating accessories, get an accessory transformer.
@William 1 posted:Yes, but sometimes these discussions roam far off the original topic, which is not a bad thing for those interested but if the guy wants a simple answer to a very basic question…
My suggestion is to operate your one uncoupling track off track power at 18 volts. Be careful with the push buttons that might stick. If you want to expand to more uncoupling/operating tracks, switches, lights, operating accessories, get an accessory transformer.
Can you explain the reasoning behind a recommendation counter to the manufacturer and the mathematical/scientific models discussed (aside from sparse empirical tidbits)?
There are quite a few examples mentioned in this thread and elsewhere on the forum where excess current through the Lionel FasTrack Uncoupling coils and similar devices have lead to meltdowns. Anyone who chooses to power them with 18VDC (contrary to advice given here and in the manufacturer's directions) is repeatedly taking a ~$40 minimum gamble each time their layout is powered up. It seems to me like a little additional precaution would be worthwhile in the long run.
I’m not arguing that point, I’m totally behind using an accessory transformer, using track power is not the ideal option for anything other than powering trains as I think I tried to say. But I might agree with the one guy that said the power applied for the short time it takes to uncouple a car at 18 volts or whatever, it only takes a bump, prob wouldn’t fry the unit, it might, but only guys with more experience know the answer to this.
I think he was looking for a simple answer, not a dissertation on whatever that was, my initial suggestion was to spend $30 on an an accessory transformer, if he doesn’t want to spend the dough I think he could get by with track power. Just don’t let the button get stuck!
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