# Any need for DC?



## gtsonoma (Dec 24, 2020)

I have the Digitrax DCS100 and will run locomotives, turnouts and other track stuff with the DCC rail bus.
The Digitrax website specs AC or DC input for the DCS100 so it seems I can build a simple 120 volt to ~14v power supply. Line cord, fuse, on/off switch and a transformer.

Pretty much all the DCC electronics have the option to be powered by the rail bus or a separate 12v DC supply. 

About the only other thing I think I need is lighting of various things around the layout, can these lights be AC ~14v ? and can they be powered from the rail bus?

I can add to the transformer a bridge rectifier, capacitor and regulator to get 12 volts DC if needed but I am not seeing much need. What am I missing ?


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## traction fan (Oct 5, 2014)

gtsonoma said:


> I have the Digitrax DCS100 and will run locomotives, turnouts and other track stuff with the DCC rail bus.
> The Digitrax website specs AC or DC input for the DCS100 so it seems I can build a simple 120 volt to ~14v power supply. Line cord, fuse, on/off switch and a transformer.
> 
> Pretty much all the DCC electronics have the option to be powered by the rail bus or a separate 12v DC supply.
> ...


 For turnouts to be switched by the DCC system, you would need stationary decoders. These receive a digital signal, just like the decoder in a locomotive, and output the DC or AC burst to operate the switch machine. The switch machine then moves the points.

Traction Fan


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## DonR (Oct 18, 2012)

You have a very powerful DCC system. Far more so than the typical layout controller. Most of
us use the 2 amp DCC systems widely available. They are powerful enuf to run several
locos at tye same time even on very large layouts. You must be 
anticipating running a number of locos WITH SOUND at the same time.. Can you give us a more complete description of your
layout plans? How many and the 'motor' type of turnouts?

Except as noted by traction fan...the DCC controller should only feed the track. The exception is if you
use stationary decoders to operate your turnouts. Otherwise, turnouts, signals, lights and other
accessories should have a separate power source. Many of us use old wall warts of the needed
12 to 15 V AC or DC. LEDs require DC.as do Tortoise type turnout motors. Twin coil motors can
be run on AC or DC.

Read the specs for your DCS100 carefully. You could damage your system with
the wrong power supply.

Don


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## mesenteria (Oct 29, 2015)

I think the lights, the pea bulbs, need DC if they're said to be DC only, but you'd have to inquire. As the others have said, most of us use other power supplies to power structure lighting and signals on the railroad. If you have turnouts slaved to decoders, then you need to power the decoder using the rails, just like the decoders resident in, and controlling, the locomotives, and for the same reason; the DCC system delivers its instruction packets through the rails.

I also have a turntable from the steam era. It has digital rail power so that locomotives will do what I tell them to do, just like elsewhere on the layout. Rails is rails! However, the power to turn the bridge is supplied by a different component, and that's a wall wart with the correct specifications as stated in the turntable manual. So, the turntable has one controller. It controls the indexed turning of the bridge....only. The power to the rails comes from the same cord that connects to the motor/drive housing under the base of the turntable. That power bus has wires that go to the rail wipers, and it's bridge control wires are also under the same insulation. But they are quite separate.


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## gtsonoma (Dec 24, 2020)

Thanks for all the input guys. My layout is all on paper currently so I have nothing to post here. Layout is in a 12 x 10 bedroom, covers 3 walls, is about 120 sq ft with a center access isle and is on 2 levels. About 100' of track, a number of sidings, spurs and a couple of reverse loops, about 24 turnouts.

Circuitron Tortise turnout motors are powered by a stationary decode, the decoder is powered by and gets it digital signal from the rail bus. Smail motors have a built in decoder and these are also powered by the rail bus. Stationary decoders like the Digitrax DS64 are powered by the rail bus. It seems pretty standard that stationary decoders do not have a DC voltage requirement.

The DCS100 is rated at 5 amps and is way more than I think I need with having 3 maybe 4 locomotives in motion at the same time.

Structure and street lighting using the grain of wheat type bulbs that can run on either DC or AC

I am still not seeing any reason to have any DC power, or am I missing something ?


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## traction fan (Oct 5, 2014)

gtsonoma said:


> Thanks for all the input guys. My layout is all on paper currently so I have nothing to post here. Layout is in a 12 x 10 bedroom, covers 3 walls, is about 120 sq ft with a center access isle and is on 2 levels. About 100' of track, a number of sidings, spurs and a couple of reverse loops, about 24 turnouts.
> 
> Circuitron Tortise turnout motors are powered by a stationary decode, the decoder is powered by and gets it digital signal from the rail bus. Smail motors have a built in decoder and these are also powered by the rail bus. Stationary decoders like the Digitrax DS64 are powered by the rail bus. It seems pretty standard that stationary decoders do not have a DC voltage requirement.
> 
> ...


With your stationary DCC decoders the only remaining reason I can think of for DC power might be for your lighting. Incandescent bulbs like the grain of wheat bulbs can indeed run on either DC or AC. In fact AC is actually better since it helps the bulbs last longer, assuming equal voltage. However, sooner or later all incandescent bulbs do burn out. Most of us use LEDs now because with a current limiting resistor and proper voltage, they last almost indefinitely. If you prefer the incandescent lighting, then I agree, you won't need DC.

Traction Fan


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## Lemonhawk (Sep 24, 2013)

The DS64's can use rail power, but I prefer to wire them to use their own power (12 volt DC wall wort) rather than waste rail power. Check out using a RS_100_15 Mean Well power supply from Jameco to power your command station RS-100-15: MEAN WELL : AC to DC Power Supply Single Output 15 Volt 7 Amp 105 Watt : Power Supplies & Wall Adapters. 12 volt or 5 volt DC wall worts are great for powering LED's with an appropriate resistor in series with the LED. I typically use a 1000 ohm 1k resistor when connecting them to 12v DC.


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## wvgca (Jan 21, 2013)

LEDs normally reqire DC, but they can be driven from AC, not sure about tortoises


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## Lemonhawk (Sep 24, 2013)

Tortorise and Switch-master are stall motor types and take DC, you reverse the voltage to them to have them change direction, but unlike solenoid operated turnout, you can leave the voltage on as the motor is designed to operate in this manner. While LED's can be driven with A/C if your bothered by the rapid blinking of Florescent lights, you will notice the blinking of the LED's as they cycle with the A/C.


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