# Rheostat for ho trains



## Jcaru (Dec 30, 2010)

I have a mrc280, which is a two cab transformer. Each cab is 14.5vdc and 8.5va (I'm assuming that is amps, not sure what the v stands for). Anyways I have 3 track that I'd like to control separately from this transformer. I'm thinking of using a rheostat to accomplish this, but I'm not sure what size rheostat i need. The trains I'm using are the bachmann Thomas trains. Any help would be great.

Thanks

- jason


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## tankist (Jun 11, 2009)

fist of all there is no room for assumption, the V in "VA" is there because it is not Ampers but Volt-Amperes . quite a different thing.

as for your main question, as far as i understand you want to regulate power of constant AC channel with potentiometer after rectifying it (which you didn't mention). i would not do this.


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## T-Man (May 16, 2008)

You are better off just using another transformer.
With a toggle switch you can alternate between two sections but to operate all three at once? Well you could use an old slot car controller, some with driving wheels held their speed Made by Aurora in the 60's. but that may tax your current transformer. You may find an old stand alone throttle at a train show they did make them.

Second Thought
Anton referred to the AC accessory terminals. It is better to get another transformer than to convert it.
IF you get the slot car controller or have one ,you will need two. It will divide the power of one of your throttles, turn it up and connect the two controllers in parrallel. You can use this for small trackage but you risk the chance of being under powered.


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## Jcaru (Dec 30, 2010)

Tankist



> as for your main question, as far as i understand you want to regulate power of constant AC channel with potentiometer after rectifying it (which you didn't mention). i would not do this.


No, I don't want to use the middle constant AC Channel for this. Is the middle channel here AC for accessories for AC accessories only? If so aren't accessory's all DC powered? This is all new to me. 

I do have an understanding of basic power, AC, DC etc...

Now I have 2 tracks powered by one cab. So when I start the trains, both go and stop at the same time. I'd like to bring power out of the this cab to a switch. Out of this switch i would "y" it to two rheostats. One for each track, so that i could separately power each track.

I'd rather not purchase another transformer now. (budget reasons). rheostats are much cheaper that transformers, and would accomplish the same thing. If my reasoning is correct.


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## T-Man (May 16, 2008)

Accessories are AC. The Switch is AC powered unless you modified it. 
The engines are DC.
You have a nice transformer, the manual.
A starter transformer from a beginner's set is very inexpensive.


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## mr_x_ite_ment (Jun 22, 2009)

Jason...I have always just brought power to the whole layout at once, but I did run the power through a small switch panel that could have three different sections branching off of it. I could turn each section on or off, but I always left them on. 

I am wondering if you would be better off switching to DCC? Just a thought.



Just to follow up...I know DCC can be out of reach for some budgets, but many of the entry-level ones are getting much cheaper these days. Some might think DCC is a complicated system, but it is actually a lot easier than the situation you are describing. With DCC, you could have the power on to ALL track, but no train would move until you "tell" it to.

Chad


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## tankist (Jun 11, 2009)

Jason, since you say you understand the basics of electric power you know about voltage drop and heat dissipation on resistances. you will need a hefty reohstat to sustain that power - i see no reason to use rheostats here.

another power pack will run you from 5$ for used simple one to 20$ nice used MRC techII. 



mr_x_ite_ment said:


> I am wondering if you would be better off switching to DCC? Just a thought.


Chad, he doesn't want the expense of another DC pack. do you really think he wants the expence of DCC system + 3 decoders? with 3 independent track DCC is not needed


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## mr_x_ite_ment (Jun 22, 2009)

Ok, maybe I don't really understand what Jason is trying to do. 3 independent tracks and multiple power packs/controllers seem complicated to me. I only suggested the consideration of DCC to possibly simplify things a bit. He is free to do what he wants, and it doesn't matter to me which he chooses.

As to whether or not something is expensive, that seems relative. I DO NOT view DCC as expensive these days. I realize that the next guy might feel it IS expensive! I realize we all have to live within our budgets. I always try to save money whenever I can.

It is good that we have a forum like this. I enjoy seeing many different viewpoints. No one is really ever wrong here...there are always more ways than one to "skin a cat!"

Chad


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## mr_x_ite_ment (Jun 22, 2009)

As a follow up...wanting to have 3 independent tracks seems like a PERFECT time to consider DCC!


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## Jcaru (Dec 30, 2010)

DCC is probably the way to go. But since i just purchased everything recently, track, transformer, track etc.. I didn't want to buy another transformer if not necessarily needed. My first thought wasn't to have 3 seperate tracks running 3 trains at the same time, but you know how that goes.

Seeing that i could buy a rheostat at Radio shack for $4, i was thinking that would be the way to go until another year or so. Wiring it this way isn't complicated.

If I went DCC what transformers would be the one to purchase? The transformer i have now is the mrc280. 
I'd like to power a minimum of 3 trains at the same time.


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## T-Man (May 16, 2008)

I have bought DC power packs for a buck.

This will work.


They go for 5 a piece, so your idea is cheaper but these have a reverse switch and brake.


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## mr_x_ite_ment (Jun 22, 2009)

Jason...It wasn't my intention to deter you from doing what you were thinking about. It just sounded to me like you might be a prime candidate to at least take a look at DCC.

I don't know anything about the other DCC controllers out there...I only know my own. I went with the Bachmann E-Z Command. It was $83. It has performed flawlessly. The only drawback is that 3 trains might be the limit on what it can power. I have run 4 before, but it is too hard to keep track of 4 by myself. Other guys' opinions would count more than mine here. Best of luck, my friend!

Chad


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## tankist (Jun 11, 2009)

purpose of DCC is a system to overcome limitation of directly controlling only one locomotive. since in OPs situation tracks are not connected he can easily control all 3 independently as is, hence no need for extra expense .

and even if OP does decide to make a jump for DCC i would not recommend EZ system. while cheap and relatively inexpensive it lacks crucial functionality - it can not program CVs directly.


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## Jcaru (Dec 30, 2010)

You aren't deterring me from what i thought about doing. I originally thought about dcc, but the transformer i was reading about was about 200 which I didn't want to spend right away. 

What do you mean nby programming CV's directly?


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## mr_x_ite_ment (Jun 22, 2009)

I absolutely agree with you, Anton. Jason certainly doesn't need DCC if his current configuration is doing what he planned. I realize that used transformers don't cost very much...so maybe staying with his current plan is best for now. Anton, you also bring up a good point that E-Z Command will not program CV's. I was going to mention that as another drawback too. I don't really care to mess around with all that, but I have run into one situation where it would have been nice to have that ability.

Jason, a CV is a configuration variable. It is an aspect of the locomotive that can be fine-tuned to perform a bit better, such as the voltage required to get a locomotive moving. I don't know anything about setting CV's, but I am sure it can be a nice feature to have at times. I always tend to stay simple...lol.

Chad


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## tankist (Jun 11, 2009)

decoders store their settings (adresses , speed curves, function outputs) in registers called Configuration Values or CVs. EZ system can't assign values beyond the basic ones, meaning if you suddenly need to troubleshoot issue with your loco, and need to reset it, you stuck going to LHS or a friend with full featured system. its not nice to have, but absolutely must have thing if you ask me. as important as keeping a basic toolkit in your vehicle for the rare but possible event when you need to change a tire.
it is CV readback that is a feature that falls into "nice to have" (and EZ system doen't have that either obviously as there is no screen)

since pre-owned system is not much more expencive then EZ i see no reason wasting money on that. might as well get full featured tool from the start.





just my 0.00002 cents


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