TVS about to order 20 from Digikey..are these correct?

Here you go Dave, All you ever wanted to know about the TVS. 

 

Five Frequently Asked Questions about System Level Transient Voltage Protection

 

Near the end of the document they discuss the placement of the TVS.  Any time you have inductance between the item being protected and the TVS, the item being protected will receive a higher voltage spike.  You can't assume that all the voltage spikes come from the TIU channel and transformer, they can come from any inductance anywhere on the layout that suddenly loses power and has a collapsing magnetic field.  Many accessories have coils that activate motion, when you de-energize the coil you have the potential to generate a voltage spike.  If the engine is next to that accessory and some distance from the TIU (and it's TVS), your protection is substandard due to the inductance posted by the track and wire between the engine and the TIU TVS.

 

Will this be an issue?  Maybe not.  However, if there was no reason to have TVS protection, why is it in the TIU?

 

 

  Dave, if i am not mistaken you are pretty much 3 rail. One tvs per engine. The tvs would be installed across your positive pick roller and the other end of the tvs to your engine ground which shares your outer 2 track rails. The tvs listed above is not polarity sensitive.

  I prefer to pull the shell and install near the board. You may be able to turn your engine over and install at the trucks from the roller to truck ground. Hoping others will chime in with how to's.

If it ain't broke,break it and make it better

I know that this is an old thread, but it is relevant.
Regarding TVS's, I just ordered 50 of the ones listed above.

My question is whether there is a direction to these?
In the DigiKey picture, I see no distinguishing marks to indicate a direction.

willygee posted:

  Dave, if i am not mistaken you are pretty much 3 rail. One tvs per engine. The tvs would be installed across your positive pick roller and the other end of the tvs to your engine ground which shares your outer 2 track rails. The tvs listed above is not polarity sensitive.

 

Just for clarification - 3 rail is AC so the pick up roller is HOT not POSITIVE.  There is no + or -from track voltage.

Wild Mary (AKA Nick) Retired & "Riding The Wild Mary"

 

 

Forum Member Since 24 Sept. 2004

 

RWL posted:

I know that this is an old thread, but it is relevant.
Regarding TVS's, I just ordered 50 of the ones listed above.

My question is whether there is a direction to these?
In the DigiKey picture, I see no distinguishing marks to indicate a direction.

The CA in the part number indicates a bi-polar device that has no polarity.

gunrunnerjohn posted:

It makes no difference, TMCC/Legacy/Conventional/DCS.  Same voltage limits apply.

 

R U sure?

I smoked a Lionel board with my Z4000 turned up too high. I have run over 25 volts to a MTH board without issue.

" on Sour mash and cheap wine " ??

Why go back to DCC when I have DCS!

Gentlemen,

   I believe you guys are playing a big over kill on this TVS matter, I have never had a spike the TIU TVS could not handle, never ever had a problem.  If you want to add TVS to all your engines have at it.  Might be something to consider with a very expensive engine, maybe.

PCRR/Dave

Never worry about what other people think, be strong and walk in the way of the Lord.

 I personally don't think it's big over kill at all. Unlike a fuse, we have no way of knowing the TVS's in our TIUs are still handling all the spikes they've been getting exposed to? Also, how well do they work in the TIU if the layout is powered in passive mode? Distance applies too. For instance, if the front truck jumps the rail on a steamer, the sparks are much closer to a TVS installed in the engine, then the ones installed in the TIU. On some big layouts the TIU could be over 50' away. Then you have the guy who's pulling 50 cars with 6 engines who's drawing high amps through a channel that could have a bad TVS. Could you imagine all 6 of those engines getting fried at once from a spike that failed to get grounded because the TVS was bad and the breaker on the brick was too slow to open. Heck, for how cheap these components are, it wouldn't hurt to put two in an engine and maybe even a re-settable fuse.  

Dave Z

Dave Zucal posted:

 I personally don't think it's big over kill at all. Unlike a fuse, we have no way of knowing the TVS's in our TIUs are still handling all the spikes they've been getting exposed to? Also, how well do they work in the TIU if the layout is powered in passive mode? Distance applies too. For instance, if the front truck jumps the rail on a steamer, the sparks are much closer to a TVS installed in the engine, then the ones installed in the TIU. On some big layouts the TIU could be over 50' away. Then you have the guy who's pulling 50 cars with 6 engines who's drawing high amps through a channel that could have a bad TVS. Could you imagine all 6 of those engines getting fried at once from a spike that failed to get grounded because the TVS was bad and the breaker on the brick was too slow to open. Heck, for how cheap these components are, it wouldn't hurt to put two in an engine and maybe even a re-settable fuse.  

Thsnks for that explanation. Very good case you make.

Engineer-Joe posted:
gunrunnerjohn posted:

It makes no difference, TMCC/Legacy/Conventional/DCS.  Same voltage limits apply.

 

R U sure?

I smoked a Lionel board with my Z4000 turned up too high. I have run over 25 volts to a MTH board without issue.

If you read back in the thread, I was referring specifically to the voltage rating of the TVS protection diode, not the voltage tolerance of the various electronics packages.

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Alan Mancus


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