Re: How DCC signal is superimposed onto AC voltage
Vollrath, Don <dvollrath@...>
Well...Yes & no. The concepts of modulating one signal (the carrier) with another (the signal) have been around for a long time. Think Radio & TV. Then add the cpmplications of color TV, then hundreds of channels multiplexed on a single cable. They didn't have microcomputers/microcontrollers when those products were invented and sold by the millions. But if you will pardon the pun, you are on the right track. Model RR products are physically small. One COULD use discrete components (Resistors, capacitors, transistors, etc.) to detect and properly decode the composite signal. But without using any integrated circuits you would be talking about thousands of components, in a really big box...And a nightmare of reliability problems. First came Integrated circuits (available in 1960's), then the programmable Microccomputers (1970's), then Microcontrollers (1980's) and other small surface mount components. The basic concepts of DCC were invented in the 1980's but used by only by one or two competitive companies. However, it is the combination of availabity of compact low cost microcontrollers, and the standardization of DCC through efforts of the NMRA, and the mass of interested modelers with money that makes it all available today. The microcontroller does make it possible to fit that much flexible logic in that small of a box at a reasonable price.toggle quoted messageShow quoted text
So, Yeah. Without the Microcontroller we wouldn't have DCC.
[mailto:WiringForDCC@...]On Behalf Of Aaron Lau
Sent: Monday, December 12, 2005 7:08 PM
Subject: [WiringForDCC] Re: How DCC signal is superimposed onto AC
Thank you very much. I have a clearer picture on how signal is
superimposed on AC.
Just for curiousity sake, since this is so simple, why wasn't this
being introduced long time ago...like in the 60's or 70's? What make
it so 'acceptable' in the 90's? The only reason I can of (not even
sure if i am right)is that the signal can only be decoded by a
microcontroller. Am i right to say that?
--- In WiringForDCC@..., Mark Gurries <gurriesm@c...>
AC power outlet. Thus when the term AC is spoken, people jump tothat
concept of what AC means and stick to it. That is not the personsfault
for that is often all they ever been exposed to (known) as thecurrent
that is flowing back and forth changing voltage polarity as itgoes at a
rate described in terms of a frequency.a
fixed 120V current that changes polarity 60 times a second.only
difference is that they step down the voltage to something safersuch as
16V. But it is still a 60Hz Sinewave.definition.
the voltage is 14.25V, 12V for N scale.traditional
definitions of AC power.signal
with another, but for DCC theshiftfrequency (or period) of each cycle of AC is changed between twodifferent frequencies to represent abinary one or zero. This is a form of integral cycle frequency
keying. For DCC the carrier ismeasuresa flat-topped rectangular AC rather than sinusoidal.
the time between them toanddetermine if a one or zero is being transmitted.
zeroes) is spelled out in thevoltagedetails found at www.nmra.org.
term, butvoltage? I tried finding websites to explain it in technical
how toto no avail.
decode it.Best Regards,
Yahoo! Groups Links