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As I said before, any foreign HO DC locomotive is compatible with US track, DCC, and accessories. The Br.218 already has the DCC sound decoder installed. NEM and NMRA standards are the same concerning supply power and DCC.

I don't know how to make that any clearer.

I've been modeling Germanic railroads for over two years now.

To answer your question, DCC can be used on AC or DC.
 

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Let me try my own answer:

All decoders marketed after about 2005/6 have been deemed 'dual mode', meaning they'll sense and operate on either DC or AC current, with the latter being DCC (digital) current with the signal embedded. Note that this is true only for decoders on factory default settings. Second hand decoders, or second hand engines you purchase with unknown decoders, or with decoders having the previous owner's custom sound levels and motion characteristics programmed into the appropriate CVs, should be restored to factory defaults by performing a reset...FIRST THING YOU DO. Why? Because many of us remove that dual mode capability by entering a value into CV29, and if you don't know this and expect your decoder to sense your DC-only layout, you will get nothing out of your locomotive. No lights, no motion, no sounds.

So, about this Roco locomotive. It is possible it has no decoder, and somehow makes sound. That would make it a DC locomotive. I've never heard of such a thing, except for the short-lived BlueLine experiment by Broadway Limited Imports about 13 years ago. But, maybe Roco is doing something similar. I suspect, however, that it merely has a 'dual mode' decoder and that it comes ready to operate on either type of track current, DC or DCC.

Your post headline asks if DCC is AC or DC. It is AC. The DECODER will respond in a rudimentary way if it senses DC current, and you'll be able to move your locomotive forwards and backwards, sound the horn/whistle, and the lights will work. But, without a DCC controller, you'll not be able to get all of the motion and sound qualities and adjustments that your DCC decoder is capable of. There's no sound level adjustment possible in DC, no motion adjustment such as inertia and momentum (CVs 3 and 4 respectively), and so on.
 

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the loco description says it uses a PluX16 DCC sound decoder. it's not clear what "Elect. system: DC" is attempting to say.

i wouldn't say "DCC is run from AC" as in AC power, but that DCC is AC, carrying both power and signalling.
 

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Discussion Starter #5
As I said before, any foreign HO DC locomotive is compatible with US track, DCC, and accessories. The Br.218 already has the DCC sound decoder installed. NEM and NMRA standards are the same concerning supply power and DCC.

I don't know how to make that any clearer.

I've been modeling Germanic railroads for over two years now.

To answer your question, DCC can be used on AC or DC.
Thanks for the clarification. I'm just trying to be cautious and understand what I'm buying since I've never bought from Europe before. It certainly is a lot simpler than I originally thought though, so this'll probably be the last post I make regarding stupid questions like this (and hopefully I'll be getting my hands on a 218 sometime soon!)
 

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Discussion Starter #6
Let me try my own answer:

All decoders marketed after about 2005/6 have been deemed 'dual mode', meaning they'll sense and operate on either DC or AC current, with the latter being DCC (digital) current with the signal embedded. Note that this is true only for decoders on factory default settings. Second hand decoders, or second hand engines you purchase with unknown decoders, or with decoders having the previous owner's custom sound levels and motion characteristics programmed into the appropriate CVs, should be restored to factory defaults by performing a reset...FIRST THING YOU DO. Why? Because many of us remove that dual mode capability by entering a value into CV29, and if you don't know this and expect your decoder to sense your DC-only layout, you will get nothing out of your locomotive. No lights, no motion, no sounds.

So, about this Roco locomotive. It is possible it has no decoder, and somehow makes sound. That would make it a DC locomotive. I've never heard of such a thing, except for the short-lived BlueLine experiment by Broadway Limited Imports about 13 years ago. But, maybe Roco is doing something similar. I suspect, however, that it merely has a 'dual mode' decoder and that it comes ready to operate on either type of track current, DC or DCC.

Your post headline asks if DCC is AC or DC. It is AC. The DECODER will respond in a rudimentary way if it senses DC current, and you'll be able to move your locomotive forwards and backwards, sound the horn/whistle, and the lights will work. But, without a DCC controller, you'll not be able to get all of the motion and sound qualities and adjustments that your DCC decoder is capable of. There's no sound level adjustment possible in DC, no motion adjustment such as inertia and momentum (CVs 3 and 4 respectively), and so on.
That's what I was originally assuming, so thanks for the clarification.
 

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Gregc, DCC, DCC is AC. It is dual mode capable conventionally for those who can't operate the decoder using AC. It will take the DC current and pass it through to the outputs, but with limited range of function. In fact, all of a decoder's outputs are rectified to DC, as one would eventually realize due to its DC can motor, DC lights, and DC amplifier and speakers. But if you want the decoder's full range of functions, you must have the digital signal, and that can only be passed to the decoder via a square wave AC current. DC, to my knowledge (I'm not an electrical engineer, not even an electrician) is incapable of carrying a digital signal because it has no wave form ("direct").
 

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Gregc, DCC, DCC is AC. It is dual mode capable conventionally for those who can't operate the decoder using AC. It will take the DC current and pass it through to the outputs, but with limited range of function.
not sure what I said that elicited this response.

yes, some DCC decoders will operate on DC if the DC voltage is high enough. The processor must just pass the rectified (max) voltage to the motor switching the polarity of the h-bridge to match the track polarity.

similarly it is possible to operate one DC locomotive, one without a decoder, on a DCC system using loco address 0. the DCC signal typically has an average voltage level of 0, half the time it has one polarity and the other half the other. but the command station can stretch the idle pulse so that there is an average DC voltage, either + or -, to drive a DC locomotive in either direction this is not recommended because even an AC current is generating heat in a DC motor across the tracks, even when the average voltage is zero.
 

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Perhaps I read more into your pervious post to mine than I ought to have. You said, "i wouldn't say "DCC is run from AC" as in AC power..." You can't power a DCC system with DC. You must plug it into an AC source suitable for the power supply powering the system, and that power supply is not a DC power supply. A DCC power supply, like my Digitrax article, outputs 15 volts AC.
I know that my Digitrax DB150 can run a DC locomotive, no decoder, using Add "00" simply by zero stretching (or rather, not) to that address.
 

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You said, "i wouldn't say "DCC is run from AC" as in AC power..."
maybe I misinterpreted the OPs original statement. can't imagine why anyone would care how their DCC system is powered.


You can't power a DCC system with DC.
you don't think a DCC system would work if I replaced the wall wart outputting ~13VDC with a car battery?
 

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There seems to be a fair amount of misunderstandings here. Limiting things to just the track power, there are DC systems (like non DCC HO), A/C systems (like Lionel) and DCC systems. The DCC output is not A/C it is pulse width modulated DC signal. The Pulse width modulated DDC signal contains packets of information that are sent to the decoders. And Mesenteria, your DB150 can be powered by either a 15 A/C or DC power supply (I have powered my DB150 with either), most DCC controllers now just use a DC power supply.
 

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I think this is a confusing area. The DCC power input is DC. It turns that into a PWM pattern (pulse width modulated) onto the track which sometimes is described as AC.

Well maybe it is technically ... But to the just knowledgeable enough to be dangerous like me ...


When I think AC I think wall current, 60 hz 120 v.
 

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i'm sure a DCC system can be designed to accept either an AC or DC output from a wall wart plugged into a ~120V AC wall socket.

the DC voltage used within a DCC system are not simply output as PWM. the ~14VDC voltage of a DCC system is applied to the track using an h-bridge, common motor controllers and used in a decoder, allowing the polarity of the output to the track to be easily reversed.

in the waveform from NMRA S9.1 below, the horizontal line represents 0V and the waveform is both positive and negative. in other words the waveform is AC (but not like your Lionel set).

 

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it is width modulated, but it is not a pulse in the sense that it goes from 0 to some voltage and back.

the NMRA standard clearly said "levels that have opposite polarity"

i would expect a red green bi-color LED driven by DCC to appear yellow. The same bi-color LED across a PWM DC signal would appear one color and when connected oppositely, the other color.
 

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All the OP wanted to know is if this locomotive will run on DC track and be able to use DCC.

Every mole hill turns into a mountain around here.
 

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Yes but I almost understood it. Getting closer. And I have a digital scope. It's mostly a paper weight. But I could put out it in the track and look at pwm signal. What I mean is I could connect the probe to the track. If I put it down n the track it would be something else.
 

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a pulse width modulated signal is typically used to create an analog voltage from a digital output by controlling the duty-cycle of the digital output to achieve a desired average voltage. DCC decoders use PWM to control the motor voltage.

but while the time between polarity changes on track voltage is used to convey the 0 or 1 digital signal value (see S9.1), i wouldn't describe the DCC signal as PWM any more than I would ethernet or I2C signals. And I'd hate to think anyone thinks that DCC drives tracks voltages using PWM to control locomotives.
 

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I thought it was an encoding scheme to embed cmd codes. I understand DCC engine side uses pid control and bemf for motor sensing.
 
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