Basic DCC question from newbie


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choffman41

New Member
I started HO many years ago but am a DCC illiterare newbie. My present layout is powered by an ohmite VT-8 variable transformer and a rectifier. It is rated at 7.5 amps output at 120v. Can I use this to power the rails and add the rest of the necessary DCC stuff or is it better to buy the whole kit? Thanks for any advice.
 

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For starters, that unit is a variable AC supply - DCC systems require a DC supply. You *could* add the proper components to rectify and filter the output into a clean DC source, but I hardly think it would be worth it. I'd be a bit nervous powering my DCC system with that regardless. Each DCC system requires a specified input voltage. With that unit being variable, you would first need to set it to the correct voltage using a meter. My biggest fear would be that somewhere down the road it might get bumped, or curious fingers give it a twist to a higher voltage and fry your system.

Also, I don't think any manufacturer would be too keen on a damaged DCC system that was powered with a home brewed supply like that.

Power supplies DESIGNED for each specific system aren't very expensive - go with components that are designed for and work together.

Mark.
 
I would echo what Mark said. Power supplies are pretty inexpensive. Actually, you can use an AC power supply with the Digitrax command stations. Read your manual carefully before connecting power.
 
OK, I see your point. Actually, I could probably sell this thing for a fair price. So as the next step, what exactly would be a good starting system for a relatively small layout with maybe two or three trains running and no exotic frills? Not looking for specifics, but maybe a general idea of what I'd need. Thanks.
 
There are DCC sets available. I'm not really familiar with what's in them as I have pieced my system together based on what I need. Digitrax has a few systems available. You certainly wouldn't need more than the 5 amp system. The radio link is a great feature to have with it so you aren't constrained to standing at a control panel. The Duplex system is a step better so you don't have to plug your throttle into the loco net to acquire a locomotive.
 
Digitrax DCS-51 Zephyr would be my choice, comes 100% complete to power a small layout like yours. In response to your original question, Lenz, NCE & Digitrax full DCC systems all work with 16-18 volts AC or DC with at least 5 amps capability.
 
choffman41 said:
what exactly would be a good starting system for a relatively small layout with maybe two or three trains running and no exotic frills?
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This is the most frequently asked question on model railroad forums today. If you search these threads there should be bunches of conversation about "the best DCC" system.

Not looking for specifics, but maybe a general idea of what I'd need.
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The basic DCC system consists of a power supply (such as the topic that started the thread), the DCC command unit, at least one throttle, and a decoder for each locomotive. Of course I always recommend one throttle for each train to be run.

NCE has the DCC-Twin (very limited but also very simple), the NCE Power Cab (full featured), Digitrax Zephyr, MRC Prodigy Advanced. I own both the Twin and a Zephyr and can recommend both for their respective niches.

When I first started in DCC I jumped straight into a full blown system. Specifically a Lenz Set 101. I soon upgraded it to wireless. Since then I also have purchased a full featured NCE Pro-Cab wireless, and a CVP Easy DCC also wireless. I can recommend any of the three. I still consider the Lenz my primary, but the NCE is getting more and more use as more and more layouts that I go to operate on use that particular system.
 
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The NCE Power Cab is easy to use and will handle the sort of layout you describe. Should you later expand your layout, NCE has an upgrade path that incorporates the Power Cab, so your initial investment in the Power Cab will always be useful.

Having said that, it's often a good idea to purchase whatever brand of DCC system is popular in your local area or local model railroad club. This gives you a built-in group of experienced users to consult for assistance.

The popular brands of DCC equipment have helpful discussion groups on Yahoo. I can speak only for the NCE group, which I find is full of terrific expertise.

- Jeff
 
Ditto what Jeff says. I would do some investigating on the DCC systems before making the plunge. I am familiar with operating an NCE, MRC and Digitrax. I think you really need to know which one will be comfortable to operate on your layout. I am most comfortable with my MRC Prodigy 2 wireles but I can also operate an NCE and Digitrax. Do some reading on the net and if you are working with a good local train shop see what they have to say. Also a good Idea is the specific forums. They usually support questions quite well and quickly.
Thanks
Wayne
 
Thanks for all the suggestions. In my ongoing research I am learning that the AC power in a DCC system is not 60 Hz so I have abandoned the idea of using this transformer. I'm going to heed the advice and buy a complete system.
 
What type of model railroad equipment runs on 120 volts?

If you only have that VT and rectifier what provides protection from shorts?
 
It's putting 12v to the tracks so I suppose the short protection would be the same as any dc model railroad power supply. The rheostat is on my control panel so if a short occurs, I just turn the rheostat down to zero.
 
choffman41 said:
It's putting 12v to the tracks so I suppose the short protection would be the same as any dc model railroad power supply. The rheostat is on my control panel so if a short occurs, I just turn the rheostat down to zero.
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Wait .... what ? You were running your trains using the dial on THAT power supply ? It outputs AC line voltage - how were you running your DC trains with it ? You could melt stuff with that thing !

As for the power on DCC rails, it is an AC-like waveform. On a scope, it looks like a square wave AC but at a much higher frequency. The DCC power supply does not connect directly to the tracks. It is fed through a command station which superimposes the information packets on the high frequency line to the track. The key is having the correct power supply to match the command station's requirements - which will vary from system to system based on the requirements. Don't try to "rig" something like that for your DCC system - it's not regulated and it's not filtered, who knows what might happen if you get any fluctuations in your line voltage. It's not worth the risk.

Besides, most all DCC starter sets and even the more advanced ones come with a matching power supply already in the package.

Mark.
 
Mark R. said:
Wait .... what ? You were running your trains using the dial on THAT power supply ? It outputs AC line voltage - how were you running your DC trains with it ? You could melt stuff with that thing !

I'm running the output through a bridge rectifier. As to the voltage, sorry, I left out an important part of the equation. I run the variable 0-120 output into a 120/12 transformer then to the rectifier. The variable transformer is really only being used for the rheostat. The track voltage never gets above about 14v max. I realize it sounds like a Rube Goldberg setup, which it is, but it was all free stuff when this layout was built a few decades ago. Anyway, I'm going to tear it all out and probably go with the Power Cab starter setup. Should be more than adequate for what I'm doing here.
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choffman41 said:
Mark R. said:
Wait .... what ? You were running your trains using the dial on THAT power supply ? It outputs AC line voltage - how were you running your DC trains with it ? You could melt stuff with that thing !

I'm running the output through a bridge rectifier. As to the voltage, sorry, I left out an important part of the equation. I run the variable 0-120 output into a 120/12 transformer then to the rectifier. The variable transformer is really only being used for the rheostat. The track voltage never gets above about 14v max. I realize it sounds like a Rube Goldberg setup, which it is, but it was all free stuff when this layout was built a few decades ago. Anyway, I'm going to tear it all out and probably go with the Power Cab starter setup. Should be more than adequate for what I'm doing here.
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Ahh... That's sounds better. Not an uncommon setup from years (and years) ago. But certainly nowhere near "state of the art" power for an DC analog railroad. The needs of DCC are much different from DC so buy an approved power supply from the maker of whatever DCC command station you choose.
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