# DC power pack with DC out for accessories?



## drabina (Mar 19, 2013)

Are there any DC power packs that will have DC out for connecting accessories? With today's LEDs built into pretty much anything, I do not think there is much need for AC terminal. Even if I were to convert the output to DC, 18V AC after rectification would give me over 25V. This is a bit too much for a few LEDs that I have. I am trying to avoid running two power supplies (one for track and one for LED accessories) and I would like to stay with one power cord for my small layout.


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## traction fan (Oct 5, 2014)

*DC output*



drabina said:


> Are there any DC power packs that will have DC out for connecting accessories? With today's LEDs built into pretty much anything, I do not think there is much need for AC terminal. Even if I were to convert the output to DC, 18V AC after rectification would give me over 25V. This is a bit too much for a few LEDs that I have. I am trying to avoid running two power supplies (one for track and one for LED accessories) and I would like to stay with one power cord for my small layout.


drabina;

I have an old MRC power pack that has constant DC output terminals, in addition to the normal terminals for variable DC (train) and AC. You might google Model Rectifier Corp. or look for a website. They may have a modern version with the DC output you want. 
If you are unable to find a pack with extra constant DC outputs, you can use resistors and/or a voltage regulator to tame the high DC voltage you would get from rectifying the AC output. I did something similar for my LED power source. I rectified the output of a 16 volt doorbell transformer and used resistors to get it down to 3 volts DC output. This works very with fifty, tiny, surface mount LEDs; connected in parallel. The LEDs somewhat duplicate, the many ceiling lights in this photo of the real Seattle Union Station. I scratch-built an N-scale model of this station. The model has fewer lights!

good luck;

Traction Fan:smilie_daumenpos:


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## GNfan (Jun 3, 2016)

If it were me, I'd look for a Bachmann "starter set" power pack at a swap meet, use a voltmeter to find the setting that gives a useful voltage and glue it in place; and use the AC output to power turnouts.


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## CTValleyRR (Jul 26, 2014)

Just out of curiosity, why do you need a power pack with a DC output? That is, why a power pack output, not why DC. If you already have an unused on, I get it, but why buy a power pack at all.

If you shop around on the internet, you can find a wide variety of wall warts providing all sorts of DC output volt / amp / watt combinations. Buy one and strip off the connector on the output side.

That's how I'm powering all of the servos that operate my turnouts.


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## drabina (Mar 19, 2013)

CTValleyRR said:


> Just out of curiosity, why do you need a power pack with a DC output? That is, why a power pack output, not why DC. If you already have an unused on, I get it, but why buy a power pack at all.
> 
> If you shop around on the internet, you can find a wide variety of wall warts providing all sorts of DC output volt / amp / watt combinations. Buy one and strip off the connector on the output side.
> 
> That's how I'm powering all of the servos that operate my turnouts.


Because I would rather have just one power cable going to the layout and simplified wiring underneath. I am building small switching layout for my kids to play with and I do not want to splice 110V wire to run additional transformers.


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## CTValleyRR (Jul 26, 2014)

drabina said:


> Because I would rather have just one power cable going to the layout and simplified wiring underneath. I am building small switching layout for my kids to play with and I do not want to splice 110V wire to run additional transformers.


I'm not following you.

You need separate wiring for the track bus and accessories anyway, so you're not saving on any wiring there. Use power distribution blocks (like this: https://www.walthers.com/12-position-prewired-power-distribution-block-rated-at-15-amps), which come in several terminal configurations, to minimize wiring under the layout. Wall wart input connects to the master terminals, accessories wired to the others.

I only have one 110v extension cord from my wall to my layout. I have mounted a power strip underneath, into which is plugged the wall wart for my servos, the plug for the MRC Prodigy Wireless, the wall wart for the Symphony 77 sound system (which my sons enjoy), leaving a spare socket for a soldering iron, minivac, hot glue gun, etc. etc.. Zip ties keep all the excess wiring bundled up neatly. The switch on the power strip is the master power switch for the layout.

Obviously, you do what you want on your own layout. But I think your requirement to use one power pack for everything is making things a lot harder than they need to be.


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## Texas Pete (Sep 28, 2011)

You can use a bridge rectifier to convert the AC accessory output of your power pack to DC. AC connects to the inner two connections (with the ~) and DC comes out the outside wires (+ and -). It's a miracle!

This particular one, the KBU4J, is rated 600v, 4 amp, should be plenty enough for your purpose. Available from electronics suppliers like Mouser and Digikey.

Pete


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## Chet (Aug 15, 2014)

I use a couple of old MRC power packs for accessories. I do use the AC output to operate my old twin coil switch machines. My layout is over 30 years old so a lot of things are old school. I use the variable DC out to power lighting, which are incandescent bulbs and signals. I drop the voltage to around 8 to 9 volts. Brightness is fine and the lower voltage probably adds life to the bulbs and some have been in use for over 25 years. 

I see no need for me to change anything at this time as everything is working fine. If it ain't broke, don't fix it.


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## sid (Mar 26, 2018)

haha funny im in the process of building a pc power supply to do just that. run any and all dc accessories . ive even found a very cheap controller to control speed of my engines with the adition of a couple toggle switches to reverse them. all in a very compact 2x2 box or could very well be even smaller if i think about it for a while .. pc power was free from old pc the controler for speed was $5 the toggles were 5 for $6. not bad for $11 bucks and a lil time sodering the toggle. have enclosed pic of the controler for speed . i disasembled it to show size of the guts. possability of taking these and making a very small control box of my own specs , maybe three or four controlers to on box. these are dc to dc 8 amp capable. have the pc power and toggle mostly hooked up . can post pics if wanted. should add that the pc power has 12 volts dc at 12 amps plenty of juice and also 5 volts dc plus 3 volts dc lots of different voltages an amps too.


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