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.