TVS for Postwar ZW at Outlet, instead of Track Outputs... Thoughts on this??

The TVS diode protects against voltage spikes caused by collapsing electromagnetic fields generated by the layout (relays, solenoids, motors, derailments etc).

A short video about those spikes:

Since the source is layout side, you want the protection layout side. Many people put them on the track, others put them on the output terminals of the transformer, and some do both!

With a ZW, it is easy to take 4 TVS diodes, shape them like this so they wrap around the binding posts, (A-U, B-U, C-U, D-U).

bmoran4 posted:

The TVS diode protects against voltage spikes caused by collapsing electromagnetic fields generated by the layout (relays, solenoids, motors, derailments etc).

A short video about those spikes:

Since the source is layout side, you want the protection layout side. Many people put them on the track, others put them on the output terminals of the transformer, and some do both!

With a ZW, it is easy to take 4 TVS diodes, shape them like this so they wrap around the binding posts, (A-U, B-U, C-U, D-U).

 

 

Thanks for the good information and video. The girl is cute, but should consider switching to decaf  ...She was helpful though.

OK, now... is there a specific TVS I need for the ZW? That's all I have to do is get four of them and put them between the hot and common posts on the back (and that won't cause short)?? Seems too easy. I've seen so many posts with guys building highly complex sequential TVS configurations onto wood panels and nearly chucked the idea of even using the ZW again with the thought of all of that hassle.

Which TVS would be appropriate for ZW outputs?

Here is my set up for PW transformers.

For PW transformers or any transformer that can put out 20 VAC or more, the TVS model 1.5KE36Ca is recommended.  If you only use PH180 or PH135 that have a maximum of 18 VAC then you could get by with 1.5KE33Ca models.

Per Gunrunnerjohn it is best to have the TVS as close to the board you want protected as possible, so he recommends in each engine.  I put mine at the track connection.  Because the TVS has a failure mode that is not detectable I also put one at the transformer as a backup.  I'm also thinking about adding them at the terminal block.  They don't impact operations and the are cheap.

For me it was a late addition, about 30 years. I use GG track and added the TVSs with Marx lockons. I also added fuses for the old ZWs.

The multi-receptacle power strips with surge protection provide the protection from the house side for the 120 supply. The other option for that is to have an electrician install the surge or lighting protection in the breaker panel or the supply to it.

I don't have that - a nearby lightning strike, lot next -door, surged through the ground and the weak link, which was Verizon FIOS equipment that was not protected. Fried various items throughout the house. I now have the power supply and their grounds protected.

That was most likely a once in a lifetime event, so the track protection should be the primary concern with a surge protected power strip for the 120 supply for the layout. 

Lightning can enter the house directly through the wall bypassing all protection. Yep I too had electrical damage from lightning so the power strips to the trains get unplugged from the wall when not being used. AND lightning can easily jump a wall switch as well. Don't underestimate lightning.

Jim

Is a TVS directional?

Jim Harrington posted:

Is a TVS directional?

Jim,

The TVS you need for this application are bidirectional. The recommended 1.5KE36CA is as seen on page 6 of the datasheet: http://www.mouser.com/ds/2/389/CD00000663-250565.pdf

Make sure the TVS units are bi-directional or they won't work. I bought around 15 TVS units from Mouser Electronics and installed a few so far, but will install the others soon. The TVS needs to be installed either at the transformer output or at the track power hook-up and must be installed going from positive to neutral.

Lee

Here's a direct link to the TVS I use: 1500W 36V TVS at Digikey

In looking a the way these are connected across common and hot, and with the desire to have them as close to the sensitive electronics as possible, can these be installed at locations in each each track block from inner to outer rail, rather than in the connecting wiring?

-Jim

Jim,

Now that is an interesting question.  I don't think that has been discussed before.  It seems like it would work as long as there is a TVS is between the engine and the transformer. I think this would include all possible routes between the engine and the transformer at the point of the short.  Let's see what others have to say.

The TVS can be placed between a hot and common anywhere, including directly on the track.

You can place them anywhere you like across the track power.  Some folks have tied them directly to the track at selected locations.  If I have an engine open for other work, I frequently put a TVS inside across the track power feed.

So in  a locomotive, is would be connected to the pickup roller and frame ground?

(since I have one open now...)

Yep, directly across the track feeds.

I just ordered these from Digikey, based upon this very informative thread, thank you all.

I do have an additional question, as mentioned above, if the TVS's have an undetectable failure mode (unlike a fuse) do they need to be replaced after a spike or other triggering event?

You will never know if a TVS has failed open without testing it out of circuit.  However, they are not like a fuse or a MOV device in that they will handle many surges over their lifetime without degradation.  If they failed shorted, you'll know, if they fail open, there's no way to know.

Thank you John. That clears it up for me.

Also thanks to all who posted photos and diagrams. As soon as my parts arrive, I'm ready to go.

John,

I looked at the link that you provided.  I'm curious though, how does one know if the TVS is non-directional or not???  I saw no mention of that.

thanks - walt

From the specifications of the part in the link.  It's a one channel device, and it has one bidirectional channel.

thanks John.  i ordered 25 of them after reading your helpful reply.

- walt

CAPPilot posted:

Here is my set up for PW transformers.

For PW transformers or any transformer that can put out 20 VAC or more, the TVS model 1.5KE36Ca is recommended.  If you only use PH180 or PH135 that have a maximum of 18 VAC then you could get by with 1.5KE33Ca models.

Per Gunrunnerjohn it is best to have the TVS as close to the board you want protected as possible, so he recommends in each engine.  I put mine at the track connection.  Because the TVS has a failure mode that is not detectable I also put one at the transformer as a backup.  I'm also thinking about adding them at the terminal block.  They don't impact operations and the are cheap.

Thanks for all of the great information. Will these do the trick then for all power supplies mentioned?

http://www.ebay.com/itm/QTY-10...4:g:RIAAAOSwcwhVQGNY

DDOTCDOT, those only provide 600W of protection, others are recommending 1500W protection.

bmoran4 posted:

DDOTCDOT, those only provide 600W of protection, others are recommending 1500W protection.

These then?

sorry miscopied the wrong link last time 

https://www.ebay.com/itm/181336444076

Yes, the 1.5KE36CA is what seems to be generally recommended around here.

Why in the world are you going to eBay and paying top dollar for those TVS diodes when Digikey will sell you 25 for the same price as the 15 on eBay?

Digikey shipping on small orders is only $3-4, so you're shopping in the wrong place.

gunrunnerjohn posted:

Why in the world are you going to eBay and paying top dollar for those TVS diodes when Digikey will sell you 25 for the same price as the 15 on eBay?

Digikey shipping on small orders is only $3-4, so you're shopping in the wrong place.

Actually, John, I don't know if you can make out my screenshot, but what I see is 15.95 for 25 of them, and only 2.50 for shipping... That's about $0.50 - $1.50 cheaper for me, than 15.97 + 3 or 4 for shipping via DigiKey... unless I'm totally missing something here, I apologize, I know you're trying to be helpful, and I am new to this, but I think my math is right.

The ones you specified have a band, so they're not the bi-polar type.  Those will not work for AC.

From the ad you posted, note the cathode band.

gunrunnerjohn posted:

The ones you specified have a band, so they're not the bi-polar type.  Those will not work for AC.

From the ad you posted, note the cathode band.

It is not uncommon for a generic picture to be used. Product description and part number match up exactly, including "Polarity:Bidirectional".

It may be "common" not to have the real picture, but if I have the choice to buy my parts from a reputable nationwide electronics distributor or eBay for the same price, the choice is very easy in my mind!  I know for sure that the parts that I get from Digikey will be the ones I ordered.  It's hard to say what you get from eBay, I've received stuff not as described any number of times.  Typically, the folks selling that stuff on eBay are surplus parts dealers or are just selling off some parts that they didn't use or have received and have no use for.  YMMV

Here's the confirmation email I just got from DigiKey for my order of 25 of them:

Your total cost is $20.14 in U.S. currency, including $3.03 postage.
We have billed this to your Visa credit card.

One more question so bear with me!  I'm not electrically smart so what is intuitive to many is not to me.

I'm wondering this: if I have 17 lockons, with track power flowing thru each, and put a TVS device on each one, I still have 8 left over.  Does it do me any good to put 8 lockons at various places with a TVS device on them WITHOUT having those 8 lockons connected to the track power source???  Kind of like 'stand alone' TVS devices.

I hope that question is clear.

thanks - walt

There is nothing wrong with that Walt in terms of TVS, but have you considered your accessory buss?

I only have a Christmas-time layout.  My accessories are powered from a separate trannie than those used for track power.  Accessory wires never touch anything that track power wires touch.

I humbly admit not understanding your question though.  Thanks for your comment on my initial question.

- walt

Just asking about accessories because some of the modern ones have circuit boards that may appreciate protection as well.

I got my order from Digikey today. Flawless and perfect and an American company! Thanks to Gunrunner John for the suggestion. I now have a reliable source for electronic products. I highly recommend them.

Now on to the install!

If Digikey doesn't have it, sometimes Mouser will have it, they're another excellent resource.  I order from other sources as well, but those are my two "go to" places when I want parts fast and of known quality.  It doesn't hurt that they're pretty cheap as well.

bmoran4 posted:

There is nothing wrong with that Walt in terms of TVS, but have you considered your accessory buss?

I gave the accessory comment some more thought:  If TVS devices are to capture spikes, why would an accessory experience a spike?  Remember, I use a completely separate trannie for accessories than the trains.

On a similar note, if the accessory protection makes sense, do you think it would be a good idea to protect my Miller signs since they each go for $40 to $60 and I have 12?????  Can a spike, if that's the right word, come thru a wal-wort?

thanks - walt