I've plunged for 10 amp W28s for the museum layout. They pop fast enough to suit me under a dead short at 1/4 throttle on the ZW, and there's plenty of margin for running anything up to and including a twin Pullmor GG1... 
Mitch
Here is the AirPax Instant trip times:
Here is the W28 series trip times (I've colored the area where the best of the W28s fall behind the protections of the Instant AirPax above):
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SteveH, bmoran4, GRJ, everyone—
Thanks so much for your kind replies/ thoughts/ advice on picking either the 7.5 or 10 amp rating of the Airpax breakers for my ZW. Right now my layout has totally separate double-track mainline loops. Per loop, I am running only a single engine of various types (Legacy diesels, and steam) with occasional running of 5- 1950’s Santa Fe aluminum passenger cars with TMCC Santa Fe A-A units with a total of 2 motors. Wire feeds to each loop are 14 gauge wire. I also want to be able to run 2 separate trains/ engines on one of the double track loops. Layout is approx 30’ long x 12’ wide.
So I will go with the (4) breakers of 10 amp ratings for each of the 4 outputs of the ZW.
Again, thanks for your help.
Carl J
Wondering if these Airpax 5 amp pp-11-0-5.00A-OA-S breakers are ok to use. I understand the '0' indicates instant, and the 5 amp rating....past that I am not sure if these are suitable for our applications. Thanks in advance, Jeff
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Well, they will limit you to a 5A maximum current on the tracks. If that isn't an issue, they'll work great. 
Thanks John!
@jeffrey O'Brien 082418 Yes those look fine and should operate like the PP11-0-5.00A-OB-V. The difference is the ones you're asking about come with Faston to screw terminals adapters. Where did you find them?
Steve, I found them on ebay. Seller had 4 of them, paid just over $30.00 for all 4 shipped. I thought that I would give the 5 amp a try given the price, then I noticed that the product numbers were not quite the same as in the pictures of the ones you have posted. Thank you for clearing up my concern; and thanks for all the research you have shared with forum members regarding the Airpax breakers.
For anyone wanting the Airpax 7.5A Instant breakers, they appear to be back in stock at Online Components
@jeffrey O'Brien 082418 Thank you for passing along your source for the 5A screw terminal variety.
@SteveH posted:For anyone wanting the Airpax 7.5A Instant breakers, they appear to be back in stock at Online Components
@jeffrey O'Brien 082418 Thank you for passing along your source for the 5A screw terminal variety.
I got some of mine from them and some of them from Sager Electronics.
John
Steve, thanks so much for this wonderful thread. I read it through several times with a good sleep in between to make sure I understood your input. I have ordered the breakers from the sources you listed. I ordered 2 each of 10, 7.5 and 5 amp. Half are back ordered till later this spring, but at least I have a plan. I am just now getting back into trains. When I last ran trains (in the 1970’s) it was O gauge tubular 3 track Lionel’s from the 50s. While my brother now has that set, I have been buying various old stock and accessories from that era. I now have about 100 ft of track and most of the other stuff I need and purchased a refurbished Lionel ZW (R) 275 amp transformer.
Again, it is my intent to run only the old stock, only on the old track. Engines, a few lighted cars and some decouplers, lighted buildings and street lights. I intend to have inner and outer tracks, switches, and a number of sidings. Overall size is about 8ft x 12 ft with several levels (mountain), etc. I was particularly excited to see your thread about running the 4 “terminals” independently and having breakers on each… new idea that was very helpful.
So, with that in mind, here are my questions (and please… excuse the ignorance… any experience I had as a kid was rudimentary and my one electrical engineering class was 35+ years ago). First, I have no clue what that diode is all about. What it does or how it works. Your helpful diagram shows the line coming out of the terminal (and thru the breaker), connecting to the middle track and coming back via the outer track to the common closing the circuit. But tangential to that and not in line with it the diode is just connected across the two lines. What does that do and how does that help. Additionally, there is another one just hanging out on the other side of the track. It is all perplexing… again, excuse my ignorance on the topic.
Secondly, my layout as a kid was an outer and inner loop. One power connection near the transformer and of course loss of power on the other side (and now I know why). But when I added an additional small loop off the side (and put power on it), as the train crossed over into that area the train would immediately reverse direction. I went off to college soon there after and never “solved the issue”. Off to army and life so… here I am building a new one and need to ensure I can hook up my power at multiple points on multiple loops and sidings that I can turn on and off. I’m sure it was a simple fix but… a little help as I begin laying this out to wire would be great.
Final question (for now), I have a number of those Lionel connections and was intending to use them to connect my power by “clamping” them to the track. But I have seen a number of people talking about soldering wires for a more positive connection. Had never seen that done. I have both the skill and equipment to do so… is that how you all suggest I connect power? Thanks again. Wonderful thread!
@Chills posted:...I have a number of those Lionel connections and was intending to use them to connect my power by “clamping” them to the track. But I have seen a number of people talking about soldering wires for a more positive connection. Had never seen that done. I have both the skill and equipment to do so… is that how you all suggest I connect power? Thanks again. Wonderful thread!
Let me say that just about everything you said count me in.
Re the above, the other complicating thing for the CTC lock ons is if you buy new tubular track from Menards, they will not fit without adjusting to the clamping posts, and even then they will sometimes disconnect if you bump them. I've spent a lot of time trying to see why things aren't running only to find out that the lockon is off.
Based on the OPs recommendation I bought 2 'PP11-0-10.0A-OB-V ' from onlinecomponents.com, and they should arrive today.
Sorry, another question already… I won’t have the first of the airpax breakers in till next week so haven’t held them in my hand. How do you all connect them? Is it just a spade style connector?
@Chills posted:Sorry, another question already… I won’t have the first of the airpax breakers in till next week so haven’t held them in my hand. How do you all connect them? Is it just a spade style connector?
It depends on the configuration of the breaker. I know of at least two variations. One has screw terminals, and another has tabs. I believe the tabs can accept TE FASTON connectors, or a soldered connection.
Answers follow:
@Chills posted:Steve, thanks so much for this wonderful thread. I read it through several times with a good sleep in between to make sure I understood your input. I have ordered the breakers from the sources you listed. I ordered 2 each of 10, 7.5 and 5 amp. Half are back ordered till later this spring, but at least I have a plan. I am just now getting back into trains. When I last ran trains (in the 1970’s) it was O gauge tubular 3 track Lionel’s from the 50s. While my brother now has that set, I have been buying various old stock and accessories from that era. I now have about 100 ft of track and most of the other stuff I need and purchased a refurbished Lionel ZW (R) 275 amp transformer.
Thank you for the kind words and I'm glad you found this thread to be helpful. If you would like to order the out of stock breakers, there are other distributors besides Online Compnoents. Domestically, Octopart.com is a good resource for showing which distributors sell various electronic components. Just type in the exact make and model number of the part you're trying to find.
I think you mean a 275 Watt ZW transformer.
@Chills posted:First, I have no clue what that diode is all about. What it does or how it works. Your helpful diagram shows the line coming out of the terminal (and thru the breaker), connecting to the middle track and coming back via the outer track to the common closing the circuit. But tangential to that and not in line with it the diode is just connected across the two lines. What does that do and how does that help. Additionally, there is another one just hanging out on the other side of the track. It is all perplexing… again, excuse my ignorance on the topic.
TVS diodes (link here) clamp high voltage spikes which is why they connect in parallel with the Hot and Common. The way they work is they become conductive only when the voltage across them exceeds their threshold. Derailments lead to rapidly changing voltage differences on the track circuit which causes electric coils (found around the layout in motors, transformers, solenoids, relays, and electromagnets) to force current to continue flowing as the voltage fluctuates rapidly due to the bouncing of train wheels, especially at switches. These voltage spikes are well above the component ratings on sensitive electronics found in newer command control locomotives and occur at a very high frequencies. The reasons for multiple TVS diodes around the layout is that even though the TVS diodes clamp the voltage to a safe level in one place, just inches away the high frequency voltage can be approaching a hundred volts. Unless, you're using MTH's DCS control, more distributed diodes are best (however if using DCS, the capacitance of multiple TVS diodes can degrade the DCS signal). My example showing only two was just to show how they connect. As far as where to connect them, the closer they are located to the sensitive electronics they're intended to protect, the better. I like to actually install them in more expensive locomotives right at the Control Circuit boards' power inputs from the track. Other good places are near transformers, any other coils and switches on the layout.
@Chills posted:Secondly, my layout as a kid was an outer and inner loop. One power connection near the transformer and of course loss of power on the other side (and now I know why). But when I added an additional small loop off the side (and put power on it), as the train crossed over into that area the train would immediately reverse direction. I went off to college soon there after and never “solved the issue”. Off to army and life so… here I am building a new one and need to ensure I can hook up my power at multiple points on multiple loops and sidings that I can turn on and off. I’m sure it was a simple fix but… a little help as I begin laying this out to wire would be great.
This sounds like it may have been a brief power interruption caused by a short unpowered or insulated section of track (maybe in the switch). These can be easily diagnosed with a multi-meter to find out where power is being interrupted.
@Chills posted:Final question (for now), I have a number of those Lionel connections and was intending to use them to connect my power by “clamping” them to the track. But I have seen a number of people talking about soldering wires for a more positive connection. Had never seen that done. I have both the skill and equipment to do so… is that how you all suggest I connect power? Thanks again. Wonderful thread!
Soldering is a great way to make secure track connections. Which method you choose is a matter of personal preference.
@Chills posted:Sorry, another question already… I won’t have the first of the airpax breakers in till next week so haven’t held them in my hand. How do you all connect them? Is it just a spade style connector?
The models of breakers provided in the original Topic Post at the beginning of this thread all have "spade" connectors. The female connector that attaches to them is a 0.25" Faston connector.
I was about to fire up my track with my brand new CAB-1L and BASE-1L, with my ZW with tvs diodes connected across the pairs of the 4 posts, and connecting my ppii-0-10.0a-ob-v circuit breaker. This would be to run my brand new TMCC capable 18565 loco. I remembered this thread, so I went back to look at your diagram. I didn't notice the first time that you have 2 diodes connected. I'm guessing that's not a mistake, but is it necessary? Then again, I don't want to fry my new stuff.
The closer the TVS diode is to the engine the better it works. Ideally it should be installed in the engine. Short of that, putting them on the tracks in multiple locations is a close second.
John
@texgeekboy Please see the second part of my post just before yours to see an explanation of where TVS diodes should go to provide optimum protection of the electronics in locomotives. To answer your question, extra TVS diodes are not necessary but are good insurance.
Sorry, late in replying... busy week or so. back to the TVS diodes. so if I connect them along various places on the track (I'll be running about 70 ft in total), I am (for example) using a snap link and then wiring this up between the two connections? sorry, again this type of protection is new to me. secondly, it is "absorbing" the extra voltage to reduce it? does it burn up (ie I have to replace it after each event) or somehow dissipate the voltage after? this may work even if the breaker doesn't blow? thanks for tolerating the many questions. I appreciate all the help this thread and the members have provided.
A circuit breaker protects against current overloads. It goes in line with one of the power leads to the track. You only need one.
A TVS diode protects against voltage overloads. It goes across the power leads to the track. Several, spaced around the layout are recommended.
Mike
@Mellow Hudson Mike posted:A TVS diode protects against voltage overloads. It goes across the power leads to the track. Several, spaced around the layout are recommended.
To be technically correct, the TVS protection diode protects against transient voltage spikes, it won't handle a continuous voltage overload.
Got it. can someone post a pic of how they connect their TVS diodes. thanks
Connect the TVS diode directly across the load like you' were trying to short it out. Here's a popular TVS part that's good for model train voltages.
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@Mellow Hudson Mike posted:A circuit breaker protects against current overloads. It goes in line with one of the power leads to the track. You only need one.
A TVS diode protects against voltage overloads. It goes across the power leads to the track. Several, spaced around the layout are recommended.
Mike
Ok, let's try it again:
A circuit breaker protects against current overloads. It goes in line with one of the power leads to the track. You only need one.
A TVS diode protects against voltage overloads (of short duration, i.e.. spikes). It goes across the power leads to the track. Several, spaced around the layout are recommended.
Mike
@Chills posted:... back to the TVS diodes. ... it is "absorbing" the extra voltage to reduce it? does it burn up (ie I have to replace it after each event) or somehow dissipate the voltage after? ...
Yes, TVS diodes absorb higher voltage spikes by shorting them out when the voltage across the 1.5K39CA diodes exceeds about 38 volts.
TVS diodes are unlikely to fail under normal circumstances (like the voltage spikes caused by derailments) after a single event. It should take many such events to cause them to fail. If/when they do fail, there are two possible failure modes:
- The most common, is they can fail in a permanently shorted condition. It should be obvious when this happens because they will trip the breaker.
- The much less common way TVS diodes can fail is that they fail in a open state and will no longer provide voltage surge protection. This is more difficult to test for and is the reason some people replace them regularly. Testing for this second failure mode can be accomplished by removing them from the layout and briefly connecting them to an independent voltage source slightly higher than their breakdown voltage (37.1 volts) and measuring current through them. If they no longer conduct sufficient current above the breakdown voltage, they should be replaced.
@Chills posted:... this may work even if the breaker doesn't blow? ...
In the event of a derailment, the TVS diode is designed to clamp the voltage spikes to a safe level coming from multiple sources on the layout (transformers, coils and motors), and an appropriately sized breaker will disconnect the current from the main power source (transformer). Both the breakers and the TVS diodes should work instantaneously in unison to reduce the risk of damage to sensitive electronics.
@SteveH posted:If/when they do fail, there are two possible failure modes:
- The most common, is they can fail in a permanently shorted condition. It should be obvious when this happens because they will trip the breaker.
- The much less common way TVS diodes can fail is that they fail in a open state and will no longer provide voltage surge protection. This is more difficult to test for and is the reason some people replace them regularly. Testing for this second failure mode can be accomplished by removing them from the layout and briefly connecting them to an independent voltage source slightly higher than their breakdown voltage (37.1 volts) and measuring current through them. If they no longer conduct sufficient current above the breakdown voltage, they should be replaced.
There are actually three failure modes. As Steve says, the predominant failure mode is shorted, this is the most common failure mode. They can also fail open, and finally degraded.
The typical method of testing a TVS is by using a curve tracer or simply a current limited power supply and a voltmeter or 'scope. Most times if the TVS isn't shorted, the only way you'll know if it's defective is by removing it from the circuit for testing. Given the low cost of the TVS device, that's typically counterproductive. Once you're removed them from the circuit, most people simply replace them if they suspect they're compromised open or degraded. Testing would be far more expensive than the replacement part.
I'm with @Chills, a pic is worth a thousand words, especially for the electrically illiterate such as myself. This is a picture of the motor area of my brand new 6-18565. My guess is to solder on the tvs diode to the 2 circled contact points. Would that be the proper thing to do? If not, what should I look for? Also, if the diode is connected directly to the engine, do I need one connected to the track? I was planning on connecting diodes to each of the 4 posts on my ZW, along with adding a circuit breaker.
Thanks.
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I was planning to install a TVS diode in the location you marked as well as where track power enters the control board, but some of the more experienced forum members including @gunrunnerjohn advised against connecting a TVS across the motor, because if it shorts it would likely cook the motor driver circuit.
Below is a picture of the generally accepted best place to install a TVS diode inside a locomotive. On this one, it connects between the black wire that runs from the frame ground ( common from outside rails) and to the red wire that comes from the center rail pick-up roller. The connections are spliced into these red and black wires as close as possible to where they connect to the motor control board. Even though yours is a TMCC diesel and this one is a steamer, the track power connections to the boards are similar and enter through the rectangular black 6 pin molex connector (shown disconnected for clarity), but the wire colors may be different on yours. You will need to trace the wires to determine exactly which ones in this connector correspond to track power center roller (hot) and frame (common).
Note that I protected the bare diode leads and connections from shorting against the shell and any other components using heat shrink tubing.
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@texgeekboy posted:I'm with @Chills, a pic is worth a thousand words, especially for the electrically illiterate such as myself. This is a picture of the motor area of my brand new 6-18565. My guess is to solder on the tvs diode to the 2 circled contact points. Would that be the proper thing to do? If not, what should I look for? Also, if the diode is connected directly to the engine, do I need one connected to the track? I was planning on connecting diodes to each of the 4 posts on my ZW, along with adding a circuit breaker.
Thanks.
Wrong, that's across the motor armature. The TVS diode wants to go across the track power inputs to protect the electronics. The motor driver outputs are designed well enough to deal with the transients coming from the armature, and that's also what the 1.0uf blue caps are for.
EDIT: I see Steve beat me by a few seconds.
Ok, thanks Steve and John. That was very helpful in helping me understand what it does and probably required more questions than necessary. I am NOT running the new fancy computerised stuff and at this point, nostalgic enough that I am happy with the ‘50s-‘60s post war diesels and steam engines. So, IF I am understanding all of this correctly, it sounds like I can just be content with the TVS diodes on each circuit coming from my transformer AND a few around the various loops on the track (correct me if you disagree… and think I should still put one in the engines). All that having been said, if you could indulge me with a few pics of how YOU are connecting them to your track, that will help me in making my final decisions. Also, thanks for the thoughts on failure. I will just plan an easy way to attach and plan to just replace them periodically. You guys have been an immense help as I jump back in after all these years.
@Chills posted:Ok, thanks Steve and John. That was very helpful in helping me understand what it does and probably required more questions than necessary. I am NOT running the new fancy computerised stuff and at this point, nostalgic enough that I am happy with the ‘50s-‘60s post war diesels and steam engines. So, IF I am understanding all of this correctly, it sounds like I can just be content with the TVS diodes on each circuit coming from my transformer AND a few around the various loops on the track (correct me if you disagree… and think I should still put one in the engines). All that having been said, if you could indulge me with a few pics of how YOU are connecting them to your track, that will help me in making my final decisions. Also, thanks for the thoughts on failure. I will just plan an easy way to attach and plan to just replace them periodically. You guys have been an immense help as I jump back in after all these years.
If you're running older equipment, the Airpax Breakers are still a good idea (in my opinion), but most operators would say the TVS diodes really aren't necessary because 50's-60's era equipment doesn't contain sensitive electronics and are fairly robust compared to the newer command control trains.
Yes, I agree with the breakers and have them on hand for when I get to the wiring phase of my layout. And that’s good to know about the diodes. Perhaps I will hold off on those unless or until I decide to buy some of those new trains.
@SteveH, Thanks. I'll be looking at the wiring as you described tomorrow. I should be able to find it out.
With the tvs diode installed in the TMCC engine, and that is the only post-1960 piece of equipment on my track, do I still need the diodes on the track? I will, of course, have a circuit breaker installed as per your diagram.
@texgeekboy posted:@SteveH, Thanks. I'll be looking at the wiring as you described tomorrow. I should be able to find it out.
With the tvs diode installed in the TMCC engine, and that is the only post-1960 piece of equipment on my track, do I still need the diodes on the track? I will, of course, have a circuit breaker installed as per your diagram.
In my opinion, to protect any single device with sensitive electronics, TVS diodes should be in at least a few other locations distributed around the layout to quickly dampen the high frequency high voltage spikes bouncing around the track circuit, especially near coils, transformers, and turnouts.
With only one diode, that signal would bounce around longer in time before dissipating. This would also place greater strain on the one diode in the locomotive, reducing it's longevity.
Maybe an sound analogy would be helpful in understanding this concept.
Lets say that the track circuit is like a large room with a bare concrete floor, walls and ceiling. The voltage spikes are like someone standing in this room clapping their hands a few times in quick succession. The sound will reverberate for a relatively long time after the person stops clapping in this sonically reflective space.
To shorten the time sound waves bounce around the room (like transient voltage spikes), thick carpet is added to 1/4 of the floor area (like TVS diodes) , but in practice this addition doesn't change the sound quality much, because it only covers a small fraction of the total surface area of the room. To make a more noticeable difference in the rooms' ability to absorb sound waves more quickly, more of the room needs to be covered with absorptive materials.
In the track circuit, more even distribution of TVS diodes will shorten the time the transient waveform bounces around (this is called ringing).
@SteveH posted:In my opinion, to protect any single device with sensitive electronics, TVS diodes should be in at least a few other locations distributed around the layout to quickly dampen the high frequency high voltage spikes bouncing around the track circuit, especially near coils, transformers, and turnouts.
You have to be careful sprinkling TVS diodes around if you run DCS. The parts we use are a fairly high capacitance and will quickly damp out the DCS signal on the tracks if you get carried away installing them.
In truth, if you're really concerned about spikes and your expensive engines, take the time to install a TVS in each engine across the track power input wires. That's the very best place for them, and you will also only add the stray capacitance for the engines that are actually on the active powered up tracks.
A related issue re circuit breakers and diodes. I was doing some stuff to my layout today and noticed that my fastrack operating track (uncouple/unload) wasn't behaving well. I isolated it and still had problems. Turning it over and looking at the wiring, one of the wires going to the uncoupler had melted. I did have a short a month ago (again, all postwar stuff, nothing modern). At the time I did not have diodes installed or a circuit breaker. I imagine a circuit breaker could have prevented that, right? Or, should I put a diode somewhere (instead or in addition) on the operating track wiring (a specific 'X marks the spot' would help a lot)?
The best protection (before a meltdown occurs) is the Bourns MF-R050 PTC re-settable fuse combined with replacing the factory control switch that is notorious for sticking in the On position. I'll edit this reply with a link to another thread showing how to install them which also includes more info about this melting issue with Fastrack Uncoupler electromagnets.
EDIT: Here are links to a couple of other threads relevant to the uncoupler coil melting and how to wire in protection:
https://ogrforum.com/...4#158674373762400784
and
@SteveH posted:The best protection (before a meltdown occurs) is the Bourns MF-R050 PTC re-settable fuse combined with replacing the factory control switch what is notorious for sticking in the on position. I'll edit this reply with a link to another thread showing how to install them which also includes more info about this melting issue with Fastrack Uncoupler electromagnets.
I bought a Lion Chief Polar Express set for a young relative and augmented it with some switches and uncoupler tracks. I found out two things after buying the parts: (1) the uncoupler track requires 10 volts AC so it cannot be connected to the Lion Chief power source and (2) the factory control switches both stuck. What was Lionel thinking? For a company that likes to advertise the "plug and play" compatibility of its accessories, the uncouplers are anything but. I understand they are not specifically labeled "plug and play" but still, they don't have to be the direct opposite.
I traced the wires from the pickups (center and outer). The center wires were yellow, and the were joined together with a wire connector and red wire was output. The outer rail wire was black. I found the molex like your pic. Now a final, and embarrassingly basic question. I expose some of the red and black wire before the molex, and then solder one end of the diode to the exposed red wire, and the other end to the exposed black wire, right? I couldn't discern that detail for sure from your pic. I have shrink tubing as you suggested.
I don't want to make any assumptions on a brand new engine. I am a quick learner, so I won't be asking this again!
To the TVS diode leads (which I trimmed to ~1/2" inch) , I opted to connect short wires to each before connecting those extensions into a three way splice (one 3-way splice for each of hot and common). The other 2 wires going into each of the 3-way connections are the cut ends of the original wires running into the molex connector.
This allowed a little more flexibility positioning the diode amongst the wire bundle, easier replacement of the diode later on, and enough room to slide the heat shrink tubing into position after soldering. I did try to make the extensions as short as possible to keep the diode as close in the circuit as possible to the board, without actually soldering it to the board.
Here's another picture with a wider overview.
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