For this years Christmas display I'm running a TMCC equipped K-line Hudson in a 4x12  oval layout. I've yet to acquire any remote accessories so will run in conventional mode. Should I have any concerns using the older transformer with the TMCC electronics? 

I follow the curve - The track rules.

Original Post

 Nope - just use TVS Diodes as prescribed all over this forum. 

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).

 

 For power supplies in excess of 18VAC, such as your ZW, use the 1.5KE36Ca diodes.

If you only use supplies that are limited to 18 VAC then you could get by with 1.5KE33Ca diodes.

Obviously, the best place for the TVS is in the locomotive.  However, that being said, that's also the most difficult place to put them as you have to do every locomotive!  I'd consider putting them at the track connection for the power.

Ted, the dumb part is that they don't equip the locomotives and other electronic rolling stock with a TVS!  It's dirt cheap insurance.

bmoran4 posted:

 Nope - just use TVS Diodes as prescribed all over this forum. 

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).

 

 For power supplies in excess of 18VAC, such as your ZW, use the 1.5KE36Ca diodes.

If you only use supplies that are limited to 18 VAC then you could get by with 1.5KE33Ca diodes.

Thank you Bruce, your comments along with the PBS video made perfect sense and an easy learning session. I learned about this very topic from the world's best physics professor, Dr. Prucha at Wis State Univ - Whitewater, way back when I was a young'n! Sadly, he is no longer with us, but his legacy is about a man wwho loved to get up in the morning, get dressed up into a suit and tie, and go teach physics to a bunch of kids, and he had a smile the whole time as he spoke with his slight Polish accent. 

Sorry for the digression, sometimes peeps just want to share a very good memory 

Back on topic - I like to parallel a pair of tvs diodes wherever possible because a) they're cheap, and 2) that offers an increased level of protection against the rare open tvs diode, plus 3) I believe it might offer better current handling to prevent the catastrophic (to the diode) shorting failure. Sooo much cheaper than a new board!

So I called my local hobby store looking for diodes. Told them what I was doing and the information given here. They said it wasn't necessary to add these. Something about the sine waves are cut by half??? I'm a novice with this type of stuff.  They did mention they had disconnected the electronics for a customer and rigged locomotive to start in forward motion only. Confused on what to do.

I follow the curve - The track rules.

SilverChief posted:

They said it wasn't necessary to add these. Something about the sine waves are cut by half??? 

Unfortunately, your LHS misunderstood your ask and purpose of the TVS diodes. They are somewhat correct in that a traditional diode would act the way they are attempting to articulate, but completely missed the full context and provided inapplicable advice.

It is also unfortunate that most LHS likely don't stock TVS diodes just like they don't stock transistors, resistors, or capacitors. You need to use an electronics supplier.

Favorites online are digikey.com, mouser.com, newark.com. You can also find some on the 'bay as well. Just enter in the part number into their search:

bmoran4 posted:

 

For power supplies in excess of 18VAC, such as your ZW, use the 1.5KE36Ca diodes.

If you only use supplies that are limited to 18 VAC then you could get by with 1.5KE33Ca diodes.

 

SilverChief posted:

So I called my local hobby store looking for diodes. Told them what I was doing and the information given here. They said it wasn't necessary to add these. Something about the sine waves are cut by half??? I'm a novice with this type of stuff.  They did mention they had disconnected the electronics for a customer and rigged locomotive to start in forward motion only. Confused on what to do.

Maybe you should have asked where they got their engineering degree.

Couple of comments, first, if you are running engines with electronics in them (like Lionel's TMCC), you need this protection. If you are running older PW type equipment with no circuit boards in them, you do not need this protection - you did not mention what you're running.

Secondly, your local hobby shop is not the place to look for TVS diodes, I'm sure most won't have them. Instead, go to Digi-Key (buy in quantity for cost savings) or for cheaper (but slower shipping) on the old interweb - Here's an example

Your local hobby shop guy's comments about wiring a locomotive to start in forward only makes no sense to me unless his board was ALREADY burned out, and he wanted a quick and CHEAP fix just to get the engine rolling again

 

From watching the video and understanding.... what I think is happening ..... If you just slowly power down a transformer you should not ever have any problem  .. Looks like only when you stop something that is running  and decide to shut it off  ... is this right ?

SilverChief posted:

Follow up question - If in the future I use a smaller transformer will  the diode 1.5KE36Ca work or will I have to get the 1.5KE33Ca?

It isn't so much the "size" of the transformer as much as it is the maximum operating voltage of the transformer.

In general, for up to about 24VAC, the 1.5KE36Ca is a good universal catch all solution.

Some operators get very pedantic and because their power supplies only push 18VAC maximum, they decide to go with the 1.5KE33Ca even though a 1.5KE36Ca would be perfectly acceptable for 18VAC as well.

DanssuperO posted:

From watching the video and understanding.... what I think is happening ..... If you just slowly power down a transformer you should not ever have any problem  .. Looks like only when you stop something that is running  and decide to shut it off  ... is this right ?

Not necessarily - relays switch at full power, motors are consistently changing poles... the list goes on...

Besides the TVS diodes get an ATO fuse holder ( https://www.amazon.com/Parts-E...Holder/dp/B003N8SD9G ) and some 5, 7.5, or 10 amp ATO fuses. The fuses and holder can be picked up at any local auto parts store. Inset the fuse holder in line with the power wire to the center rail. The circuit breaker on the postwar ZW is no where near fast enough for modern trains. I run the TVS diodes and 10 amp ATO fast blow fuses between my postwar ZW and TIU. I've had no issues hurting PS2, PS3 or TMCC locomotives. 

Santa Fe, All the Way

GeoPeg posted:

Couple of comments, first, if you are running engines with electronics in them (like Lionel's TMCC), you need this protection. If you are running older PW type equipment with no circuit boards in them, you do not need this protection - you did not mention what you're running.

He literally says it in the first sentence

 

SilverChief posted:

For this years Christmas display I'm running a TMCC equipped K-line Hudson in a 4x12  oval layout. I've yet to acquire any remote accessories so will run in conventional mode. Should I have any concerns using the older transformer with the TMCC electronics? 

 

Music, trains, boneless chicken farming
David

All this help and effort.... I have the diodes and had intended to purchase the reconditioned ZW.... Now I'm thinking to just get the ZW-L and forgo adding all these extras.  All my other locomotives have TMCC so I might just bite the bullet and future proof my planned layout. 

I follow the curve - The track rules.

EscapeRocks posted:
GeoPeg posted:

Couple of comments, first, if you are running engines with electronics in them (like Lionel's TMCC), you need this protection. If you are running older PW type equipment with no circuit boards in them, you do not need this protection - you did not mention what you're running.

He literally says it in the first sentence

 

SilverChief posted:

For this years Christmas display I'm running a TMCC equipped K-line Hudson in a 4x12  oval layout. I've yet to acquire any remote accessories so will run in conventional mode. Should I have any concerns using the older transformer with the TMCC electronics? 

 

Ooops! Must have had trains on my mind!

GeoPeg posted:
EscapeRocks posted:
GeoPeg posted:

Couple of comments, first, if you are running engines with electronics in them (like Lionel's TMCC), you need this protection. If you are running older PW type equipment with no circuit boards in them, you do not need this protection - you did not mention what you're running.

He literally says it in the first sentence

 

SilverChief posted:

For this years Christmas display I'm running a TMCC equipped K-line Hudson in a 4x12  oval layout. I've yet to acquire any remote accessories so will run in conventional mode. Should I have any concerns using the older transformer with the TMCC electronics? 

 

Ooops! Must have had trains on my mind!

I actually laughed and was just bustin' chops.   All good...besides, trains on the mind is more than an acceptable excuse

Music, trains, boneless chicken farming
David

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