# Best TMCC Circuit Protection?



## Bob B. (Feb 7, 2013)

I'm using an MRC Pure Power Dual transformer to provide track power to my TMCC controlled locomotives. This transformer has a circuit breaker for each side but I'm thinking I need a faster acting circuit breaker to protect the electronics in my TMCC locomotives.
Can anyone recommend a good piece of equipment to do this? The Lionel 6-1478 lock-on isn't rated for the amount of power the MRC transformer is capable of supplying. Could I still use that item to protect my trains? Thanks in advance for anyone's input on these questions.


----------



## walter (Jan 31, 2014)

From what I gather, you can use a Lionel 73-4120 direct lockons. They provide protection, but believe you need to purchase a cable to connect transformer to the Lock-On. (can't understand why they don't have regular connector nuts).
http://ri.search.yahoo.com/_ylt=A0L...-250.pdf/RK=0/RS=mBKup6Zg3C.NBfju7h5Q8PJQ1JY-


----------



## gunrunnerjohn (Nov 10, 2010)

You should also use a TVS Protection diode across the track feed. This is the one I use.

1.5KE36CA at Digikey

I'm pretty surprised that the TMCC Direct Lockon doesn't have one, but I looked and it's not there.

I personally don't like the TMCC Direct Lockon, it doesn't keep the power off, keeps banging it back on until you turn it off yourself. When I have a power trip, I want it to stay off until I fix things!


----------



## walter (Jan 31, 2014)

Thanks, I also am surprised that Lionel doesn't provide this, especially the newer ones.


----------



## Lynn D Bennett (Jul 27, 2013)

Gunrunnerjohn:

The part you recommended is for over voltage protection. It is a Zener diode that clips AC at high voltage. How does that help when the track is shorted and the power source is trying to deliver max current?

I would think a fast acting circuit breaker or FastBlow fuse would be better than relying on the circuit breaker in the power source.

Bob B.:

I know nothing of the MRC Pure Power Dual transformer circuit breaker but if it doesn't trip immediately from a derailment a person needs better protection. I offered a discussion here several months ago on what I found for a fast acting circuit breaker (that works!) in a post about the MTH 100 watt Power Brick whose circuit breaker was so slow the 20 amp TIU fuses would blow instead. Do a search on my posts to see the details.

LDBennett


----------



## gunrunnerjohn (Nov 10, 2010)

Lynn, it's not a Zener diode exactly, and it's for a different type of protection. The TVS doesn't eliminate the need for over-current circuit protection. Fuses and/or circuit breakers do not offer any protection against high-voltage spikes, that's what the TVS is for. Some additional information...

What Are TVS Diodes


----------



## Lynn D Bennett (Jul 27, 2013)

John:

Yes, it's not a zener in the traditional sense but a protection device for high voltage transients. 

I thought the poster was after protection for high current. Or are you just saying that in addition to fast action current protection you need this transient protection too?

I'm not up to speed on what can be expected in the way of transients on the rails of a toy train layout but my first reaction is that transient suppression is not necessary and only nice to have. With the exception of a lightning strike to the power lines (not very likely in my location, the High Desert of So Cal) I can not imagine what would cause the transients. It may be my lack of experience in this area that makes me think these devices are not necessary (???). Can you offer some experience on this? Do the tracks end up as a transient magnets?

I'm not arguing for or against but just want some enlightenment.

Lynn


----------



## gunrunnerjohn (Nov 10, 2010)

Lynn, high voltage transients can be generated any time power is removed from an inductor. That can be a motor, switch coil, operating accessory coil, and even your locomotive motors. Obviously, transformers are a good place to generate them as well.

This is a very common damage issue with solid state logic. I spent many years designing avionics for the commercial and military aircraft, and we were a major user of TVS protection as well as many other EMI measures.

If it has semiconductor logic, it's not a bad idea to use TVS protection. Of note, the MTH TIU includes a TVS diode in each output channel as a standard feature.


----------



## Lynn D Bennett (Jul 27, 2013)

John:

OK...you are correct. My aerospace experience did not include electromagnet devices or inductor components. My stuff was pure digital electronics. I did not think about the control of motors, etc. for a toy train layout.

About 6 months ago I finished a digital control system for my point to point wall HO trolley layout. It included three Arduino micro controllers. It randomly stops and starts the trolley at three stations for random stop intervals and includes momentum for stops and starts, all digitally done. The speed control is pure pulse width modulation. The final output was a simple analog switching amplifier that feeds the track and runs the trolleys one at a time. I have no transient protection on this layout. I have not suffered any losses to that final stage yet. Maybe there is a failure in my future(???).

With my use of MTH DCS TIU/AIU I'm protected, apparently. Good. The poster was after one of the Lionel digital control systems I believe which needs transient protection in your opinion, I presume.

Lynn......


----------



## walter (Jan 31, 2014)

Wire them across the output of transformer, or at the tracks? I just wired one across the transformer output, or should say the Powermaster.


----------



## gunrunnerjohn (Nov 10, 2010)

Lynn D Bennett said:


> OK...you are correct. My aerospace experience did not include electromagnet devices or inductor components. My stuff was pure digital electronics. I did not think about the control of motors, etc. for a toy train layout.


While some of my designs interfaced with electromagnetic devices, the TVS protection was primarily for lightning/Induced EMI protection. The lightning tests for Level A equipment that is exposed to the environment is non-trivial!


----------



## BigAl56 (Dec 14, 2011)

For my layout I use these 7 amp panel mount breakers. 

http://www.digikey.com/product-detail/en/W28-XQ1A-7/PB188-ND/45068

I install them into the side of my control panel as shown below in series with the feed to the block. You could just as easily mount them to the side of the layout. There is a companion locking washer that goes with them for securing them to wood panels. 

I also use 3 amp breakesr on the layout for protection on lighting and accessory shorts.


----------



## Lynn D Bennett (Jul 27, 2013)

The trick with Circuit Breakers (CB) is they must be fast acting. Most run of the mill Circuit Breakers are not. If CB's are not fast acting then, in the case of the MTH DCS TIU, the 20 amp breakers inside the TIU blow. That was the problem I had when I relied on the CB in the MTH 100 watt Power Brick. What a pain to have to pull the TIU off the layout and remove a bunch of screws just to change one blown 20 amp fuse. After doing it about a half dozen times (from common derailments suffered in the early stages of my layout build) I installed a fast acting CB (magnetic trip instead of heat trip internal design). I also went to Passive Mode for the wiring to keep the heavy current of a derailment out of the TIU. 

Better CB's have speed curves in their specifications. The ones I chose trips in about one second at the specified rating. Mine is an AirPax CB. To find a fast acting one I had to buy one surplus. It works as desired.

LDBennett


----------



## gunrunnerjohn (Nov 10, 2010)

FWIW, those 7A breakers that Al is using sure look exactly like the breakers that the Z1000 uses.


----------



## Lynn D Bennett (Jul 27, 2013)

John:

Looks can be deceiving! 

Without the specs you really have no idea of how "Fast" the CB is. In searching for the one I bought, most that I found readily available had a 10 sec or slower response time whereas the one I found surplus was a one second response CB. It appears these fast response time ones are not that popular and not always in stock at electronic supply houses. They are cataloged so they can be had. But they might be (??) special order. The key, I think, is that they are magnetically operated and not heat operated. The inductance of the magnetic coil seems not to effect the DCS signal as most of my layout is a "10" when I run the test using the appropriate signal strength commands in the remote DCS controller.

LDBennett


----------



## gunrunnerjohn (Nov 10, 2010)

Magnetic breakers are far more expensive, I'd bet money that those that Al has are thermal breakers.


----------



## Lynn D Bennett (Jul 27, 2013)

If the thermal breaker in a MTH 100 watt Power Brick is too slow then adding another thermal CB in series seems to me to be futile and no help. 

But a lot of money can be saved by having just one expensive magnetic CB vs. a whole bunch of potential ineffective cheap thermal ones.

Of course it depends on the usage. In my case I use the fast CB to protect the fast 20 amp fuses inside the MTH DCS TIU because the MTH 100 watt Power Brick CB is waaay too slow acting.

Just saying!

LDBennett


----------



## BigAl56 (Dec 14, 2011)

Surges are part of the game of running PW trains. That's why the breakers I use are not fast acting nor do I want them to be or they would be constantly tripping. They are thermal and there is a cool down time before they can be reset. According to the specs they trip within 4 seconds at 100% current. 

They work great and have protected my layout for years without a catastrophic failure.


----------



## gunrunnerjohn (Nov 10, 2010)

PW trains and modern electronics are two totally different things! It's pretty hard to cook a PW locomotive, much easier to do it to one of the modern command versions.


----------



## Lynn D Bennett (Jul 27, 2013)

Here's the problem and why I say for my case (and that of anyone using the MTH DCS TIU/AIU system) that a fast acting CB is absolutely necessary.

If you rely on the MTH 100 watt Power Brick CB to protect your TIU then it won't. It is so slow the 20 Amp (!!!) TIU internal fuse blows before the MTH Power Brick CB heats up enough to click the power off. Several reason that is bad:

1) Allowing 20 amps to pass through the TIU channel might eventually damage it. It is solid state and excessive current is the demise of most solid state devices.

2) To replace the fuses you have to remove the whole TIU from its mount point on the layout in order to remove all the screws.

3) There are MANY screws to remove and replace to get to one of the four fuses. I did this about six times (!!) from simple derailments before "fixing the problem" with the fast acting CB

Please note that if you have the Lionel 180 watt Power Brick I am told (by gunrunner john) that the CB is fast enough by itself. But they have been out of stock new for months and months. The last time I asked Lionel for a due date for sale, they could not give one. They are on the used market for almost the new price, in some cases.

If your layout is powered and controlled in some other way with a different system from my MTH solution then you may or may not need the fast acting CB. Also note that I said the response time was about one second (according to the specs for my CB). A one second "transient" is not transient at all but some kind of a problem.

We all have different experiences and get to choose how we do things. The above is my solution based on my needs and may not reflect your needs at all.

LDBennett


----------



## gunrunnerjohn (Nov 10, 2010)

The 20A fuse in the TIU is there to protect the traces on the PCB. However, for the variable channels the power does pass through the output triacs, and you can smoke them with 20 amps!

To date, I've never replaced the fuses in my TIUs, either the two here or the one at the club. All are powered by the Lionel PH180 bricks with an electronic breaker.


----------



## Bob B. (Feb 7, 2013)

*Scott's Odds & Ends TVS Module: any good?*

I found this website offering the following TVS module: http://shop.trainelectrics.com/Transient-Voltage-Suppressor-TVS-4.htm

"Finally - Protection for your layout against voltage and amperage spikes. With fast reacting time of less than 5 nSec, control your model railroad empire with confidence that both your trains and command system components are protected as much as possible. 

The new TVS-4 is a low voltage surge suppressor with four (4) individual channels utilizing newer generation transorb technology and spade terminals for easy hook up. Reaction time is super fast - less than 4 nSec - redirecting unwanted spikes to ground and away from our trains and equipment. Typically this is done without any interruption. 

Included is a FB-4 fuse block with 15A fast blow fuses for additional over-amperage protection. The TVS-4 performs equally well with conventional systems, Lionel TMCC® or MTH DCS™ without degradation to the command signal."

My Question: Does anyone think this module might be worth the $50 they are asking for it?


----------



## gunrunnerjohn (Nov 10, 2010)

Nope. It's four 50 cent TVS protection diodes and four fuse blocks. If that's worth $50 to you, you're a rich fellow.


----------



## Bob B. (Feb 7, 2013)

*Wiring TVS Diodes for Circuit Protection*

How does one wire TVS diodes for circuit protection? Are they just inserted between the power source and the track?


----------



## gunrunnerjohn (Nov 10, 2010)

Directly across the track feed, make it look like you're trying ti short the transformer feed with it.


----------



## Lynn D Bennett (Jul 27, 2013)

These device do absolutely nothing UNTIL the voltage on the track exceeds a specific voltage above the operating track voltage and then they short the track for the interval of the transient spike of high voltage. These are the same devices they put in computer power strips to protect against lightning strikes. If theses transients are allowed to get to the electronics they destroy transistors. The two thing guaranteed to harm transistors are over voltage and over current. Transistor are actually delicate devices and you can blow them by just touching them (static electric charge buildup on your body discharges through them, smoking them). Single discrete transistors are a bit more tolerant of handling but integrated circuits are NOT.

LDBennett


----------



## gunrunnerjohn (Nov 10, 2010)

Actually, most power strips use MOV devices, though I personally think they should be using the TVS instead.


----------



## mark d (Mar 11, 2012)

I'm using a lionel 180 w powerhouse for my tmcc layout. Would a legacy powermaster be added protection for my layout or just using the 180 w powerhouse is good enough?


----------



## gunrunnerjohn (Nov 10, 2010)

I consider it good enough. I'd simply add a TVS protection diode across the track feed for some spike protection.

1.5KE36CA at Digikey


----------



## Don Trinko (Oct 23, 2012)

Don't spend $50! I bought 100 of TVS's from ebay for a lot less than that! Don


----------



## gunrunnerjohn (Nov 10, 2010)

They're 72 cents in quantity one, and ten of them are $6.28. Where's the $50 coming from?


----------

