TIU overcurrent/ voltage spike protection

Don, were you pulling passenger cars with Non LED bulbs (incandescent)?  If yes, the third diesel could have overloaded the circuit.  If a short caused the damage you need to put fast trip circuit protection in line between your TIU and the track.

See this page on my site for detailed Circuit Protection for Toy Trains .  I really like the Polyswitches because they come in lots of sizes and are auto reset when is cleared.

Personally, I do not prefer automatically-resetting breakers or polyswitches, because the short may still be there and you then have it cycling, with a spark and possible surging.  If I'm rerailing a train and it resets, sparks which are not beneficial to electronics.

I also do not feel that the internal 20-amp fuse in a TIU is adequate protection.  If you check the manufacturer's tables, there must be an overload current of considerable duration and amperage to pop a fuse or a breaker.  I use push button marine breakers in each TIU channel output, sized to cover max load I put on that circuit and no more.  They open before the Z4000's breaker.   I have 2 channels powered by a Powerhouse 180.  My external breakers have never opened, since the PH180's is so fast.

I would suggest you test your tiu input and out put why tiu is totally disconnect from transformer n track. then use a VOM meter on ohms and I think you'll find you'll find a dead short,  due to the fact that a TVS protection diode on the input or output shorted! if you find a short you''ll have to have an asc  tech  replace the defective diodes they are designed to catch  noise spikes to protect the tiu from damage!  they due occasionally do fail and cause a short!

Alan

Susan,

Thank you for the information. I'll certainly give them a try.

Don

Alan,

Yes it has a short in Fixed 1 output. I just sent my bad tiu to an ASC MTH tech (Ray Manley) I've used before and really like. I just took a chance and tried my replacement Dash-9. It started doing the same thing the first one did. The engine noise was on, then cut out for about 10 feet, then came back on. I immediately shut down my Z4000. I think I shut it off fast enough so there was no damage. I believe there is a bad batch of boards in these Dash 9's.  I'll send the locomotive to Ray and let him verify my suspicions.

Thanks,

Don 

RJR,

I'll also look into your marine breakers.

Thanks,

Don

I use 10 amp automotive ATO fast blow fuses between my postwar ZW and my TIU. I haven't had an issue and they blow very fast. You can run 3, 5, or 7.5 amp fuses depending on the load you're running. 

TIUs have Transient Voltage Suppressor (TVS) devices built into each channel. These are the components that absorb electrical spikes and prevent damage to the electronics on your engines. It is possible that the one on your Fixed 2 channel has failed closed. That would definitely give you a short indication. Your technician may find that is all that is fried with the TIU. Actually, that's a good thing, as the TVS is doing its job and sacrificing itself. A  cheap component to replace.

Chris

LVHR

Lehighline,

I verified the short before I sent my TIU to him. We'll see what he says after he works on it. I just wish there was somebody in the St. Louis area I could take my problems to so I wouldn't have to send my  problem loco's or TIU's by UPS or USPS to get them fixed. As far as I know I'm the only one who uses  O scale MTH DCS in the area.

Don

While not inexpensive, the electronic PSX-1AC is another option and can be set to protect from 4.8 amps up to 17.8 amps (Legacy 360 PowerMaster or TPC 300/400).  It is placed between the Z-4000 and TIU.  It is a very fast multi-function CB that arrives with the automatically-resetting function active.  Switches are available to make it manual reset which is what I have done.  While it has built-in TVS I still add external TVSs (they are cheap).  Here is a picture from the manual:

With help from forum members, here is how I am wiring them:

Since you run DCS there is a downside that could add extra work.  The PSX degrades the DCS signal a bit which may impact your layout setup.  If so, you need to add a 22uH choke between the PSX and TIU.  I use a 22uH 34A choke because I run at 15.4 amps.

In normal operations, the PWR In and Track PWR On LEDs are lit.

When a short occurs, power to the outputs is instantly cut off, the Track PWR On turns off, the alarm starts and the status LED light in the reset switch lights.  Once you have fixed the short, press the Manual Reset switch and you are running again.  You could disregard the LEDs and alarm and just have a reset switch.

If you want excellent protection and having all this functionality interests you, check them out at Charles Ro.

Cappilot,

I don't care about price, paying for my TIU's and locomotives postage & repair is also expensive and time consuming. I'm having a friend over ( who does my electronic work) and I'll have him look the drawings over and see what we can work up,

Thanks for the input

Don

If this helps, here is one way to wire the PSXs in.  Looks complicated, but really doesn't add much time to add the PSX/Chokes and TVSs.

the rev l has a tiu upgrade to help prevent damage to the electronics there is a mth service bulletin about what I'm talking about ! any asc tech can install this in a rev l tiu ! the tvs diodes helps catch the noise spikes that are created from track shorts and other things that happen especially on large train layouts or club layouts especially!

Cappilot,

That does help,

Thanks,

Don

Alan,

I'll double check and make sure the TVS diodes get installed.

Thanks, Don

CAPPilot posted:

If this helps, here is one way to wire the PSXs in.  Looks complicated, but really doesn't add much time to add the PSX/Chokes and TVSs.

Would putting another PSX in between the TIU output and the MTH Terminal Block in place of the TVS 1.5KE36Ca provide better protection ?

A TVS bleeds off voltage peak surges.  A breaker opens upon overcurrent.  You can have a high voltage surge without an overcurrent, and vice versa.  So the answer is no.

RJR posted:

A TVS bleeds off voltage peak surges.  A breaker opens upon overcurrent.  You can have a high voltage surge without an overcurrent, and vice versa.  So the answer is no.

So if you have an overcurrent situation coming back from the track through the MTH terminal block to the TIU, wouldn't the PSX placed between the block and the TIU provide better protection than just the TVS, since you're saying the TVS only bleeds off voltage surges ?

"So if you have an overcurrent situation coming back from the track through the MTH terminal block to the TIU, "

Not possible with TIU in active mode.  Current flows from its source, the transformer, through the TIU and out to the track.  It can be broken anywhere in the circuit; current in a circuit is everywhere the same, and if there are several devices in parallel, the total of the currents flowing through each is precisely the total current from the transformer..  A voltage surge is generated out on the layout, usually involving a spark.  The voltage surge does not create a damaging current; it can break down a component not designed to withstand such a voltage.

Picture a water system.  The pressure is the voltage.  The volume of water flowing is the current.  I can have high pressure, but if the only outlet is a pinhole, the volume will be very low.  Conversely, I can have low pressure, and a wide open hose, and get more GPM--current-- than is flowing through the pinhole.

Richie C. posted:

CAPPilot posted:

If this helps, here is one way to wire the PSXs in.  Looks complicated, but really doesn't add much time to add the PSX/Chokes and TVSs.

Would putting another PSX in between the TIU output and the MTH Terminal Block in place of the TVS 1.5KE36Ca provide better protection ?

Richie,

My diagram is TVS overkill.  I cut and pasted a couple of other diagrams to get it.

Here is my un-knowledgeable view of a TVS.  Per previous posts, there is a TVS failure mode that is undetectable so I have at least two between the transformer and engine.  In the diagram there are four: at the track; at the terminal block; in the TIU; and in the PSX.  Also per previous posts, you want the TVS as close to the thing you want protected (engine) as possible, which is why I have them at the track.  Some here advocate putting one in the engine.

The TVS on the terminal block in this diagram is not needed.  But, as I mentioned above, they are cheap insurance.  

I have one at the terminal block because my TIUs are wired in passive mode so it is not inline with the transformer.  There is an issue with passive mode I need to learn more about, but that is another topic.

I also like the PSX-ACs, they have both over voltage and over current protection and have worked well for me here. I bought these before I decided on my main power supplies (PH-180s), so I now have PSX-ACs supplied from PH-180s feeding my TIU inputs for maximum overkill. Like Cappilot, I am using most of the PSX-ACs additional options.

My current set up was completed a little over 5 years ago and I haven't lost a TIU channel or any engine electronics and I'm happy with the overkill. I'm using a Rev L TIU, and both DCS and Legacy systems. No problems other than from operator (usually me) error. All my MTH engines are PS3, Lionel engines are Legacy and all are diesels, FWIW.

Cappilot,RTR12,

I only run with DCS @22V. You mention a 22uH 34A choke because you run @15.4. What would I need to do? I have a Z4000 going to my TIU then to the MTH terminal blocks. I do want to make sure this doesn't affect my signal strength.

Don

I wired my PH-180s directly to into my PSX-ACs input, then from the PSX-AC output to the TIU input. I am not using any 22uh chokes. The TIU outputs then run out to my MTH terminal blocks and on to their respective track drops. For each of my TIU inputs I have one PH-180 and one PSX-AC. Only using the two fixed channels right now, but have all the stuff to add the two variable channels (as fixed) when I do some layout expanding.

I have just a basic standard DCS setup (wired per Barry's DCS Companion book) and just added a PSX-AC to each channel and power supply before the TIU. Two loops of track, isolated from each other, one TIU channel per track. Each track has blocks. I wired it for DCS and added Legacy a year or so later. This setup has been very reliable for over 5 years now. 

Cappilot would be the one to clarify here, but I think he has a bit of a different setup on his layout for more power. Anyway I think it is a bit more sophisticated than mine is and also larger too.

One more thing, if you ever get any Lionel command control engines be sure to cut your power back to around 18 volts. Lionel warns against using any more than 18-19 volts with their engines as it may damage them. 

RTR12, 

Thank you for giving me a clearer picture of what I need to do. I use my Z4000 to power all inputs by just jumpering from fixed input 1 to variable 1 ( which I use in fixed mode). Same thing for fixed 2 and variable 2. So I could probably get by with just two PSX-AC's. One for each set of wires coming out of the Z4000.

I won't have any Lionel engines so voltage shouldn't be an issue.

Don

Your setup sounds fine to me. I don't think you will have any trouble, but if you do there are plenty of folks here that can help you out.  As I recall, I think putting the PSX-ACs after the TIU is what causes problems and where the choke comes into play. I have been fine here with them before the TIU though. 

Charles Ro has the PSX-ACs as noted above, but I don't think they have any of the add on items for it's options. Tony's Train Exchange has them and also all the add on accessories for their options including a screw terminal kit for connecting the wires. The screw terminals need to be soldered, but after that the wires won't need any soldering. Nice if you should ever want to change things around. Charles Ro didn't carry them back when I got mine, but Ro may have slightly better pricing on just the PSX-ACs themselves?

Good luck!

Thanks again for all your help. If I run into trouble I know where to go.

Don

One more thing I forgot to add... I also use a few TVS here and there as well, as others have suggested.  

RTR12,

A few TVS's here and there? Can you be more specific? Also did you use the same value TVS as shown the drawings above?

Keep in mind I'm no electronics wizard.

Don

I have them on the input terminals of my MTH terminal blocks as Cappilot shows in his drawing above. I have one MTH terminal block per loop of track, 2 loops. Distance to my track drops from the MTH terminal strips is not all that far right now. I plan to add more TVS when I add on to my layout, but the addition plan is not yet finalized.

If I ever get to my expansion I might consider placing some of them at the track feeds. The best place for them is closest to the device being protected, but adding too many can possibly cause problems as well. Others here are much more knowledgeable at exact TVS placement than I am. I might just be asking the same questions you are here, when I get my expansion plans finalized, if I can't decide on my own.

Gunrunnerjohn puts them in his engines, but he doesn't make a special effort to do so. He only add them when he has to open up and engine to work on it and just adds one while he is in there working anyway. As I recall he doesn't recommend taking an engine apart just specifically to add a TVS.

I just tried to reach a happy medium with them on my layout. Since I have both the PH-180s (extremely fast breakers) and the PSX-ACs I wasn't quite as worried about adding TVS's as maybe others would be without all (or any of) the maximum overkill protection I have.

I am using the same value TVS as Cappilot shows as well, same part number 1.5KE36CA. Got them from Digikey - 1.5KE36CA. I think this is also the one most folks here are using. It's been in many threads here over the years. 

RTR12,

That sounds good, 

Don

Ok, it looks like most of the circuit protection is between the Power and the TIU. We are losing signal on our TIU channels and I think the problem is a voltage spike from something in the track circuits, non derail or relays switching power on the turnouts. If that is so will PTC's or TVS offer protection between the track and the TIU Output.  When I say losing signal I mean no signal out of the TIU period. Usually takes out the internal TVS. We have 10 amp breakers between the 180 watt bricks and the TIU so there is double protection on the input side

You'll have to precisely define what you mean by losing signal---symptoms, duration, conditions, etc.  Over the past 18 years, I've had many shorts & such, and haven't "lost signal".

TVS on the output of the TIU.  Fuses and current protection are for the overload of current like a derailed train shorting the track.  Voltage spikes from coils, minor derailment and such that do not generate a large current flow are protected by TVS and capacitor circuits that absorb the spike.  The problem is the TVS can degrade and no longer absorb spikes with no way to know when it fails if it fails open.  So.... you almost need to go on a preventive maint scheme that replaces them so often.  Especially for a large layout operation like you have.  Otherwise you need to get the San Diego group to come out a help you with the Phds.    G