Talk: DCC Tutorial (Power)

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If anyone has ideas on the next topic following this page, please chime in. TazzyTazzy 19:42, 5 January 2006 (EST)

Describing DCC as a special form of DC...

I'm don't agree with the description of the DCC power on the rails as a specail version of DC... it's not really distorted DC, but is actually an amplified digital pulse stream. I think referring to the waveform as DC just adds confusion.

I didn't charge in and change things because I'm not sure if this is the same terminology that the 'official' DCC standards uses or not.

Also-- your caption under the DCC waveform mentions a mirrored wave. Do you mean above and below zero volts? Paul E Musselman - PaulMmn@ix.netcom.nospam.com


-- Actually it isn't a mirror image, since during DC stretching, the waveform can be made more negative or positive, which means it cannot be a mirror image.

Terminator (Admin)

I agree with Paul, that the illustration is misleading, at least. The illustration depicts 2 signals of equal amplitude occurring simultaneously, which would produce a null.

Robert Austin aycbob@hotmail.com



Well, if you measure both signals with respect to ground, they should null. The caption is misleading as it is simply a digital signal that ranges from a positive to negative voltage, instead of the usual 0 to 5V used in logic circuits.

(Remember, you need to be logged in to edit pages, and need a valid user account, as part of the process employed to keep the spammers out.)

Terminator (Admin) 13:06, 23 October 2011 (EDT)

Analog VS DC

Although there isn't much (welcome to add to it) in the DCCWiki Style guide, it does mention the use of analog vs DC. Analog won't be confused for DC or DCC incase someone forgets the extra 'c'. TazzyTazzy 12:49, 3 January 2007 (EST)

DCC waveform: note it is two mirror image waves

I am an electrical engineer, trying to learn about the DCC track signal. I think the picture referred to (http://www.dccwiki.com/File:DCC_wave.jpeg) is either incorrect or very misleading. It appears that the red signal, on Track A, varies between 0 and +12 volts relative to some un-stated ground, assumed to be earth ground. It appears the blue signal varies between 0 and -12 volts relative to the same ground. The differential signal between the two tracks (Va - Vb) is a constant 12 volts. (Look at the picture and do the subtraction.) A decoder in a locomotive, or a hand-held DC voltmeter across the tracks, would measure a constant voltage of +12 or -12 volts (depending on how it was connected). I must be mis-interpreting the diagram, but hopefully you can see why it appears so confusing. I think ground must be defined, and then describe the voltage on Track A relative to ground, and the voltage on Track B relative to ground. On a related note, the phrase "note it is two mirror image waves" seems more confusing to me than helpful. I don't see any mirror image waves. I see a blue wave that is offset by 12 volts from the red wave. Rick314 18:52, 24 October 2010 (PST)

DCC uses a digital signal

Be careful when trying to describe a DCC signal, remember it is not AC nor is it DC. It is a digital waveform, and the voltage can vary depending on the scale.

Trying to measure it with a multimeter is not an easy task, as they are meant for DC or 60Hz AC waveform. So the results may not be what you think they should be.

Preamble

According the the Big Book of DCC, the preamble is twelve bits. Other references are for 10 bits. Which is correct?