TVS over kill?

I think you just need one but make sure to place the TVS after the toggle.

Dale H

You can't have too many, but that may be overkill.

You are wiring them between the hot and ground, right?

Rod

At least one on every power district/'throttle output.

ThankS gentlemen I thought that was a little over the top.   I will have one for each handle of my z4000.    Btw to all those who participated in previous posts about tvs.  They were extremely helpful!    Thanks for sharing your kknowledge joe in buffalo

I'm sorry to jump in with a ultra basic question, but I thought the Z4K "protected" modern MTH engines from frying. I searched for "TVS" and understand the hazard surges and other dangers present to modern electronics.

Can someone help or point me to the correct thread so I can better understand the issues. It looks like I will finally have the opportunity to build another layout in the near future and much has changed since my last major layout thirteen years ago

Thank you

Paul

Dewey,

Thank you very much for the reply and pictures. I will take your advice and search again the prior threads on this subject. Much appreciated.

Paul

Dewey, allow me one more quick question. If the MTH TIU has TVS protection do I still need seperate protection as shown in the  pictures coming off my Z4K?

Thanks very  much.

Paul

Paul

The TIU should provide the protection. I no longer have DCS and a TIU so some experienced users should comment if different. For example, if simeltaneously running Legacy/TMCC on the DCS layout, are the engines protected by the TIU units??

If you want additional TVS units:

You can purchase TVS from Mouser Electronics:   1-[817]-804-3800

catalog #276-1.5 KE 36 CA . This TVS is bi-directional so it wires up either way. They are inexpensive--about $0.50 or less if ordered in volume of a dozen or so..

The TVS does a simple job, it clamps spikes that are greater than it's rated voltage.  It's almost impossible to have too many, so sprinkle them around.   Just kidding.

The TIU does have output TVS devices, though I personally recommend installing them in locomotives if you have them open as well.  At a minimum, you should have one installed on every power output from transformers to the tracks.  Obviously, if you don't have DCS, you don't have that output protection either.  If you have accessories with electronics, having one on the accessory output(s) is also a very good idea.

Check out this web site. They have a very informative paper on surge protection.

http://www.hirailers.org/

Also, it is a good idea to put a TVS on each input and output of any of your electrical devices like the Lionel/IC Controls products as well as any accessory that has a circuit board. The price to provide the protection is so cheap it would be crazy not to do it.

I think the TVS might have a few Pf of capacitance when used. A large number might degrade the DCS signal,I dont know for sure.

Dale H

well, I'm convinced that something can't be stopped!

I have a TIU.

I use a Powerguard on each output from my 2 trannies, meaning I'm using 4 of them.

I have 15A 35 watt fast blow fuses between the trannies' outputs and each TIU input.

Considering that I only have a Christmas layout, it seems incongruous that I have had 4 PS2 engines blow boards!  Out of 9 engines.

I don't know what's left to do!!??

- walt

Solenoid-driven accessories produce voltage spikes during regular operation.  If you have sensitive electronics (like a Dz-2500 switch machine) nearby, putting a TVS across the accessory might be a good idea.

If you read any of the posting from Dale Manquen you would find out that the QSI Powerguard do not necessarily have the same TVS components recommended on many forum threads. Install the correct TVS and forget about voltage spike issues.

This was from the BUY/SELL forum:

So, they are no longer still available at $81 + each on the Tin Rail site. I still have two purchased way back in the day from QSI wired on my layout. I sent a third one to Dale Manquen to take a part for evaluation and his report was not encouraging. As a result, [and although I left mine in place], I installed $.45 TVS in each power district for secure voltage spike protection.

Yeah Trainman, after Dale reported his finding of deficiencies I left two of my PowerGuards in place so I could watch the lights flash. But I now have multiple TVS installed for protection.

Professor Chaos DZ-2500 switch machines are motor driven not solenoid driven. Now Atlas machines are a different story.

Ron 

Motors give off spikes also when voltage is removed.

Dale H

Absolutely - it was solenoids on other accessories that were destroying the DZ-2500s!

Or at least that's what I think might have been happening.  I was having repeated failures on switches next to a mail drop and barrel loader (not precisely a solenoid, I know, but it still was generating spikes).

I put in TVSs (and snubbers for good measure) and have not had a failure since.

Ah ah. I read your post before putting brain in gear. That does make some sense. I haven't protected my dz-2500s but after reading your post I might change my mind.

Ron

Which TVS diodes to use?

I read in this OGR Forum  ( https://ogrforum.com/topic/tvs-over-kill)  that the 1.5KE36CA diode should be used for transient-voltage suppression on model-railroad circuits.

But I read in http://www.hirailers.org/techn...tm#Surge%20Protector that the 1.5KE33CA diode should be used.

So I am confused.  Can either one be used?   Is one preferable over the other?   I would appreciate some advice on this

/Ralph Platz

The 36 volt one is for a PWZW sized for when the whistle button is depressed.This peaks over 33 if the compensation winding is considered.

The 33 volt one can be used for transformers which put out a bit less such as the modern lionel brick. The 18 volts peaks a bit over 25 volts.

Dale H

I use the 36V ones, and I don't see any reason that you can't use those universally.  The small difference in breakdown voltage is insignificant as the transients we're truly concerned about are much higher than the breakdown voltage of either of these devices.

John,

Here's a question for you I've wondered about for quite awhile. I've used TVS diodes on my layout for several years now. But I don't know how you would test one to figure out if it's shot. Is there a way to do that?  In lieu of that, I just replace them periodically.

Roger

The only way to test them is to have a current limited variable power supply capable of delivering around 50 volts and ramp it up and check the point where the TVS conducts.  They are pretty robust devices and should last many years unless abused.

That's what I thought about testing. But bottom line, I guess, is that if it clamps on a spike, it's shot? Is that correct? Or would it take a very large spike to kill it? And then you wouldn't know anyway.

I just read a thread about this on a computer forum. Apparently, they use TVS to protect hard drives and when they go, the drive doesn't power up. But they said to test the diode with a multimeter and that if it reads 0 ohms, it's shot. Does that only apply to the ones used in computers?

The TVS is not like an MOV device, it can clamp thousands of transients and still be fine, they don't degrade like an MOV.  The thing that will kill them is a huge transient that simply blows them away or shorts them.

A TVS can fail either open or shorted.  If they're shorted, you'll know right away!  If they're open, the only way to know is the previous test I described.

One other "symptom" they did discuss is that it will smell burnt. LOL

Usually, if they fail open, they can be damaged visibly, but not always.

Dale H. and Gunnerjohn,

Thank you for your replies.  They clarify the question for me.

/Raph Platz

After reading this and other threads, and researching elsewhere, I'm still unclear about whether the QSI PowerGuard offers a sort of protection for sensitive DCS or TMCC/Legacy loco boards that adding the "TVS"-type device would not offer.  Having apparently fried the board(s) on my MTH UP 844 yesterday while testing it on some newly wired complex trackage with turnouts (plenty of momentary hesitations and accompanying spikes, I'm sure), the question is "not idle"! No TIU was in the circuit, since only the Z4000 transformer using conventional control was in use.  Can someone comment on this situation specifically? Thanks.

Click on link below for more information on the QSI Powerguard.

https://ogrforum.com/t...si-powerguard-review

Dale Manquen evaluated the QSI Powerguard once, I dont remember exactly what he said. From my impression, the inexpensive TVS is just as good for protection,maybe better. Also more than one can be used along the layout and even in the engine.

Dale H

I plan to power my main line through a TPC400 with two 180 PH bricks.  I run both Legacy and DCS, and I will connect my TIU in passive mode for this track.  The main line will be wired for DCS with 9 blocks continuously powered and two blocks switched for on/off operations to park trains.

I will have only one of the bricks on for most main line operations.  When I want to run multiple passenger trains with multiple engines I plan to have both bricks powering the main line.  Will the 36 volt TVS, 1.5KE36CA, be sufficient or should I use a different one.

Thanks.

Ron

Yes, install at least one. You can use a 36 volt or 33 volt one as discussed earlier.  Either one will clamp a spike to a safe limit.

Dale H