Bob and other electronic gurus, A TVS question

That's actually a Vishay (formerly General Semiconductor) part number, which you can get from many different suppliers:

http://www.vishay.com/diodes/protection-tvs-esd/pkg-1.5ke/

You're right that you need only one per circuit.  They are not particularly fragile.  You shouldn't have any trouble soldering them with any reasonable iron.

Thanks Bob, for yet another answer.  I will order in the morning.  I tried a local electronics distributor, but they did not have them at a low enough voltage rating.  (I try to use local when possible).

Dennis

I understand, (I think) from Dennis' post above.  I am further assuming, that since I feed the track power from the TIU, I can put one lead into the red & black terminal AT the TIU.  Right ?

Also, if I was to install in an engine, would it also go between ground and the pick-up roller?

Thanks, 

Don

I don't know about the colors of TIU terminals; but the TVS should go effectively between the center and outside rails of the track.  Thus, in the locomotive, between whatever the wheels are connected to and the pickup, as you say.

Thanks Bob !!!  (The TIU Red is positive to the center rail, and the black is Neg. to the outside rail.)

Thinking about it a little, And I think I will put a solder a wire to the leads on the TVS, then secure them in an area not directly attached to the TIU unit.  The reason is, I assume these units could get a little hot, and don't need to have heat generated real close unnecessarily.  

lionelsoni wrote:

I don't know about the colors of TIU terminals; but the TVS should go effectively between the center and outside rails of the track.  Thus, in the locomotive, between whatever the wheels are connected to and the pickup, as you say.

Bob, are you saying that the TVS would go across the outside & inside power wires similar to a light bulb or do you wire it in series like a fuse?  I bought a few of the TVS's from Mouser over five months ago and had trouble using one with a transformer to supply power to my switch motors. I wired it in on the power side and got nothing out of it, might the part be bad or did I wire it wrong?

Lee F.

They connect from the hot to the common wire.

In parallel, like a lamp.  If you did wire it in series, like a fuse, you wouldn't get anything through it, except any voltage spikes that exceeded its rating, that is, ironically the very spikes you are trying to eliminate. 

You know, as good of an idea as this is, I am suprised that the manufacturers don't have these wired into the transformers or available for seperate sale as a suggested add on.  With modern electronics that are so fragile, it would be a great thing.

Thanks again, Bob.

Dennis

Thanks Bob!

I just looked at the packing sheet that came with the TVS units, no instructions on how to wire it, just a shipping receipt.

Lee F.

 A couple of posters mentioned running DCS. A lightbulb placed between the center and outside rail do wonders sometimes to boost the DCS signal. I know little about electronics but have read many posts on TVS and sort of understand what they do. Just curious if they have any effect at all on the signal portion of DCS such as weakening it or confusing it. I was an early adopter of DCS and from what I remember the TIU had something built in for voltage spikes. Not sure though if it was protecting itself, the trains or both. You can never have enough protection. Would like to get some feedback from those using these on a DCS layout.

The TVS looks electrically like an open circuit until the instantaneous voltage exceeds its rated voltage, which shouldn't happen unless something (like the transformer) tries to feed a voltage spike to the track.  So I would expect no ill effect from using one with DCS.

Do TVS's have any polarity considerations?  My apologies if it's already been mentioned and I missed it.

Not if you get the right kind, which is bidirectional.  The Vishay part number is, for example, 1.5KE36CA, where the "CA" means bidirectional.  If it has just "C" then it is unidirectional and is meant for DC circuits.