Very simple help needed TVS

You really don't need a diagram. The TVS just goes direct from red post to black, or hot to common, just like you were going to short across the terminals. I have 1 to 2 foot drops from the track connected to block feeders by 2 post terminal strips. I just hooked them across the two posts on the terminal strip under the track. You can do it at the transformer if it is easier.

Excellent reply, John H.

I got this number from a gunrunnerjohn post. Is this what I need to put from red post to black post on the transformer? If reading correctly, there is no need to place a TVS anywhere other than the transformer.

1.5KE36CA at Digikey

Brent

Looks good.

No need  for more than the one, but at least one per power district , no harm / no foul for over using them where convenient. Although we are talking microseconds and the speed of light here, the closer to the component(s) being safeguarded, the better.

Like Rob says, one on each power district.  If you have a large layout, there is some benefit to having one or two at distant points across the track power.  We're not only talking the speed of light, but also any inductance of the wiring back to the transformer.  The closer the TVS is to the locomotive, the more likely it will damp any damaging transients.

Railpower distribution Terminal Strip shown for multiple rail connections on a single power district [ or loop]. Wire run to strip is from a 180 PoHo outfitted with spade lugs. Strip is Jumpered to energize all 6 screws on the Hot side and on the Common side of the strip. A TVS is connected between one of the jumpered Hots and  Common. [pictures below in reverse order].

Also shown a fuzzy photo of a TVS connected between the Hot[A] and Common [U] binding posts on a pw ZW protecting the wire run feeding the railpower district or a distribution strip as below. Can be similarly connected on all railpower posts[D, etc.]

Thanks Y'all

I now understand the terminal strip and transformer connection.

To really cover all the bases , would it be OK to install a TVS on the track ( I think this is what gunrunnerjohn is telling me)? I am using Fastrack and thinking about connecting one to the center rail and side rail at various points.

Does it matter which end of the TVS is connected to the "Hot" terminal?

Folks, your help is really appreciated and I am a real believer that the only stupid question is the one not asked.

Brent

Anywhere is fine.

They are bidirectional, so polarity doesn't come into play.

Brent,

Not sure how you have your PH180s connected to the track, but since you did not say anything about the TMCC Direct Lock-On I assume you cut off the PH180's plug.   If not, the Lock-On would replace the fast acting fuse.  Because the PH180 has a very fast CB, additional circuit protection is not used by some.

Attached is how I would do the TVSs since they are cheap insurance.  One going out to each loop, and one at each track connection on each loop.  Some would say this is overkill.

FYI, the Lionel TMCC Direct Lockon does not have an internal TVS, and it also will kill the DCS signal if you run PS2/3 locomotives.

Thanks all for this information and pictures, the PH 180's are connected direct to the Fastrack.

TVS are on order .

Thanks Y'all

Brent

In process of installing TVS on the transformers and the terminal strips, pretty simple to do but a question.

Any problem with connecting the TVS to a pieces of Fastrack at various places on the loop. I am talking about soldering the TVS to the connections on Fastrack  not to the wire.

I understand attaching the TVS to the red & black wires at FT connections.

Thanks

Brent

No problem, just note that occasionally when a TVS fails, it fails shorted.  So, you'll have to hunt down the one that shorted if that happens.  This is not an everyday occurrence, just something to be aware of.

Thanks gunrunnerjohn, another question.

How do I know if a TVS fails? 

When I decided to get trains, never did I think so much was involved, should have started a few  decades  earlier.

Appreciate all you help

Brent

You will have a short that won't be very obvious.

Any one ever experienced a tvs short?

If you have a shorted TVS, you'll know.  And yes, I've seen shorted TVS parts, specifically in the MTH TIU several times.  I've also seen them in my previous career, we used a lot of them in aerospace for protection, and they do fail shorted.  They can fail shorted, open, or degraded.  Degraded is defined when they have a breakdown voltage greater than 150% of their rating.  Here's a lot more about TVS devices.

Failure Modes and Fusing of TVS Devices

I believe some here have reported having a shorted TVS in their TIU.  If they fail open I don't think you would know?

(See GRJ's post above, he posted while I was fiddling with this one.)

this out of the link provided above from GRJ.

It's fairly easy to detect a shorted TVS, after all, they're shorted!

It's very difficult to detect the other failure modes without independent testing out of circuit.

Hi, I bought the diodes recommended here for my layout. I plan to start installing them.

One of my loops will have a toggle switch to select and AC or DC transformer. I have a British O gauge train that runs of DC. Will this bidirectional diode work with DC power? I have read about using directional zener diodes with DC.

Thanks,

George

Great info. Thanks to all for contributing.

I have a postwar ZW controlling one track which would need the TVS.

I also have 2 Z4000s controlling 2 tracks a piece with a TIU connected to both transformers. Would these 4 tracks require a TVS? I run DCS, TMCC, Legacy and conventionally.

Thanks!

George, the bi-directional TVS works fine for AC and DC.

Gerry, I'd put a TVS on the track feed from each transformer output.  It's more than the transformer that can generate voltage spikes.

Just to carry this one step further, if you use a distribution block to power your individual track feeds (such as the MTH 12 or 24 port block), this is also a great place to put a TVS, right across the red and black input posts.

Conveniently all mth 3 way posts (for use with banana plug, spade lug, bare wire) have cross holes drilled close to the base, revealed when you unscrew the plastic thumbnut. This is an ideal place to put a tvs, just stick the wires through the respective holes and tighter it up. This applies to Z4000's, TIU's, etc.

Rod

I’ve been getting a loud “pop” when turning on the power at my power strip. I installed the upper level TVS today. No more “pop”!

George

Hmmm, George, loud popping noises are never good when dealing with electrical stuff. Were you able to localize the source at all? 

Rod

Rod Stewart posted:

Hmmm, George, loud popping noises are never good when dealing with electrical stuff. Were you able to localize the source at all? 

Rod

Not really Rod. The TVS didn't completely kill it after all. I still hear it. I have all my transformers turned on with a couple that have a small load. There are two MTH trains on one powered DCS loop with lighted cars. There are 9 transformers that turn on all at the same time. I think the sound may be coming from my electrical panel, so it's likely the breaker or the panel surge suppressor I have. Six of the transformers are PH-180's on a secondary power strip. If I keep that off when I turn on the main power strip, there is no pop. Then when I subsequently turn that power strip on, there is no pop either. It's when I try to turn everything on at the same time with the one power strip that I get the pop, and not every time. I think I have a little too much on the one power strip, all turning on at once. 

George

gunrunnerjohn posted:

George, the bi-directional TVS works fine for AC and DC.

Gerry, I'd put a TVS on the track feed from each transformer output.  It's more than the transformer that can generate voltage spikes.

Thanks gunrunnerjohn!

I once worked for a company that used power outlets with MOVs (metal oxide varistors) installed on them for all their field equipment. I had some fairly powerful audio equipment that had that nasty 'pop' when turned on. Borrowed a MOV equipped outlet from work and installed it to power all my audio stuff. The nasty 'pop' was gone, never to be heard again. I think some of the outlet strips with surge protection use MOVs. 

No idea how these would work with our train power and command systems, but might be worth investigation? Maybe GRJ or Stan or one of the other knowledgeable electronic folks here could explain whether they have a place in power to our trains or we should avoid using them? They might not be so good with Legacy due to the use of the ground for the Legacy signal, I really don't know?  

I use power strips for all my train stuff too, but they are only the inexpensive type and don't think they have any surge protection, just a bunch of outlets all in a row.

Just throwing this out as an idea to possibly eliminate the 'pops', and hopefully for further comment by those more knowledgeable.  

An MOV is a different animal than the TVS.  The MOV actually degrades every time it experiences a surge, the TVS will fail if it gets hit with a surge sufficiently over it's rating, but small surges do not degrade the part.

TVS diodes

• Clamp at lower voltages
• Do not degrade with time
• Have low capacitance, suited wherever signal sensitivity is a high priority e.g. USB ports
• More expensive

Varistors (MOVs)

• Clamping voltage is higher
• Degrade over time even when used within specification and become more conducting
• More effective at protecting circuits that requiring high capacitance
• Have greater tolerance for high energy/temperatures used on high voltage environments, e.g., power mains
• More cost effective

Thanks GRJ, I didn't know they degraded over time. I no longer have it to examine it's wiring or the MOVs. 

When posting above, I was thinking about the reported problems that can happen with the Legacy/TMCC systems when using power strips to power the base. Didn't want to cause any problems for anyone.  

Even thought the TVS diode has significant capacitance in the larger sizes, the MOV has even higher capacitance.  I think they're used in power strips simply because they cost less.  Personally, I'd prefer the TVS in the power strip as it doesn't degrade, so my 5 year old power strip would still have surge protection.

George S posted:

Rod Stewart posted:

Hmmm, George, loud popping noises are never good when dealing with electrical stuff. Were you able to localize the source at all? 

Rod

Not really Rod. The TVS didn't completely kill it after all. I still hear it. I have all my transformers turned on with a couple that have a small load. There are two MTH trains on one powered DCS loop with lighted cars. There are 9 transformers that turn on all at the same time. I think the sound may be coming from my electrical panel, so it's likely the breaker or the panel surge suppressor I have. Six of the transformers are PH-180's on a secondary power strip. If I keep that off when I turn on the main power strip, there is no pop. Then when I subsequently turn that power strip on, there is no pop either. It's when I try to turn everything on at the same time with the one power strip that I get the pop, and not every time. I think I have a little too much on the one power strip, all turning on at once. 

George

Hey George,

I would guess the load pop is due to the momentary current in-rush to the main power switch you are using, especially if you are using an inexpensive switch on a power strip.  Even if there is little or no load from the downstream transformers to the layout upon start-up, there is initial in-rush. This amp in-rush causes a noticeable arc popping sound in the switch as the current "jumps" as the switch contacts come together.  The higher the in-rush, the more arcing you will have.  This will eventually cause the switch to fail (burn out the internal contacts).  In-rush current is used a lot when starting motors, but it applies here as well.

A couple of things you can do about it.

1. As you have already done - limit the number items being turned on all at once.
2. Purchase and install a switch that is rated for the in-rush current. There are options here. 
   * A commercial grade wall switch may work.  Look for a 20 or 30 amp rated wall switch.
   * The next step up would be to install a "motor" switch.
   * Install a cycle duty breaker/switch.  For example a Square D QO series house breaker would work. This actually may work the best. It will cost you the breaker, the small box to mount the breaker in and some small electrical parts.
   * Another option, which is probably way overkill, would be to install an electrical disconnect.

The other issue folks may have comment on is:  If there is this much in-rush, could this affect the initial voltage output downstream and cause harm to items.  You will need to consider any live load attached to the the transformers upon power-up and determine if this initial low voltage could cause a problem.

Please note - amp and voltage go hand in hand.  Initial low voltage will have initial high amps and vice versa.

Hope this helps.

Dave

George S posted:

Hi, I bought the diodes recommended here for my layout. I plan to start installing them.

One of my loops will have a toggle switch to select and AC or DC transformer. I have a British O gauge train that runs of DC. Will this bidirectional diode work with DC power? I have read about using directional zener diodes with DC.

Thanks,

George

George, ever think about adding either a Dallee E unit or ERR TMCC to your Britt train so all would run on your AC power with TVS diodes ?          j

JohnActon posted:

George S posted:

Hi, I bought the diodes recommended here for my layout. I plan to start installing them.

One of my loops will have a toggle switch to select and AC or DC transformer. I have a British O gauge train that runs of DC. Will this bidirectional diode work with DC power? I have read about using directional zener diodes with DC.

Thanks,

George

George, ever think about adding either a Dallee E unit or ERR TMCC to your Britt train so all would run on your AC power with TVS diodes ?          j

She’s a collectible version, and I didn’t really want to open her up. I have the DC power supply and the wiring is installed to switch it. I guess it’s and option. If I went that route, I’d go with ERR and would probably have it professionally done.

George