Hornby DCC systems

The Hornby blurb re the Elite unit says it outputs 15V AC power with superimposed signals. Tried to look at this on my rather duff scope, but can't lock on. Need to know the frequency of the "constant" 15V , ie. is it

50 Hz standard UK domestic mains, or something else? Whatever it is I'd like to know ( as usual, no response from Hornby itself.). Help appreciated. steve
Reply to
steve marchant
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Reply to
Graham Harrison

Reply to
steve marchant

Nooooooo....... I thought only our merkin cousins assumed "AC" means lethal voltage 50Hz!!!

The basic unit of time is nominally 58us (microseconds).

The data is binary and a 1 is sent as 58us one phase, 58us the opposite phase (ie the output polarity reversed).

A normal 0 is sent as nominally 100us in each phase, in practice 116us makes things easier.

So, the theoretical absolute maximum data rate is 8.6kbits/s for an endless stream of 1 bits. This never happens in practice and the actual data rate will vary between 4.3 and 8.6kbits/s depending on the data.

To drive a single unchipped loco "stretched zeroes" are use where one phase is lengthened up to 10000us to add a DC bias to the DCC signal and cause an unchipped motor to move. This is not a good idea and should be avoided since (1) some motors (especially coreless) do not like it and (2) the stretched zeroes reduce the effective data rate meaning commands to decoders are refreshed less often.

MBQ

Reply to
Man at B&Q

Being pedantic it's NMRA, not MNRA. As I understand it Lenz "invented" DCC but then (by agreement) the NMRA became the "owner" of the standards. I believe that although NMRA is a US organisation their DCC working groups include people from a number of countries. Despite the published "standards" I'm not sure everything from different manufacturers inter works quite the way it should.

Reply to
Graham Harrison

Actually, Keith Guterriez invented DCC; he called it CTC-16. See:

# "Introducing the CTC-16: A 16-channel command control system you can build", Keith Gutierrez, Part 1, Model Railroader, Dec. 1979, pp. 64-67 # "The CTC-16: A command control system you can build", Keith Gutierrez, Part 2, Model Railroader, Jan. 1980, pp. 86-93 # CTC-16: A command control system you can build, Keith Gutierrez, Part

3, Model Railroader, Feb. 1980, pp. 89-92 # "The CTC-16: A command control system you can build", Keith Gutierrez, Part 4, Model Railroader, Mar. 1980, pp. 89-93 # "CTC-16: A command control system you can build", Keith Gutierrez, Part 5, Model Railroader, Apr. 1980, pp. 71-77 # "The CTC-16: Epilogue", Richard C. Kamm et al., Model Railroader, Dec. 1980, pp. 132-136 (pp. 54-55 from Mar. 1991).

In 2003, Gutierrez was granted a patent on his system:

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The concept was developed by others, including Lenz, who arranged with NMRA to make his version of the command protocol (ie, the data format) standard. Since DCC was first adopted on a large scale in the USA and Canada, the NMRA standards became the de facto standards worldwide (as a several manufacturers who tried to go their own way have discovered to their cost).

Initially, NMRA left a large number of features as Recommended Practices, and also left the majority of CVs unspecified. The result has been a mess, which NMRA is trying to remedy by developing an expanded set of standards. At the very least, one would think that the sound chip makers would use a common standard for sound-related CVs and function numbers, etc. Not so, and I know for a fact that some manufacturers (and therefore I too) have lost sales locally because of incompatibilities. They better get their act together, IMO.

That being said, the basic functions (direction, speed, and addressing) work as intended on NMRA compliant devices.

cheers,

wolf k.

Reply to
Wolf K

Lenz developed and patented his system c1978. Presumably because of the cost of patenting, he only patented it for Germny/German speaking countries. The rest of the World was/is open market.

The NMRA took it up as their "DCC Standard" and have extended it's capabilities in conjunction with Lenz.

Regards, Greg.P.

Reply to
Greg.Procter

Err, the Lenz system has been around since 1978. Maerklin was the first firm to offer it to the public (but in a modified format to cover the 16v AC reversing) Arnold followed up with a DC compatible DCC version produced in conjunction with Ma's products. It was well established by the time the NMRA ratified it as their standard.

You're confusing "Digital command control" with Digital Command Control (DCC). The first being a description and the second a name for a specific system.

Regards, Greg.P. NZ

Reply to
Greg.Procter

"Greg.Procter" wrote

Just out of interest where & when did Hornby's Zero 1 system come into the equation, and would you even class that as (a simplified form of) DCC?

John.

Reply to
John Turner

From memory that was about 1974/5. (memory subject to date inaccuracies)-8 Zero 1 carried a digital control signal. As I said to Wolf, "DCC" is a name, d.c.c. or digital command control is a description and the two shouldn't be confused.

Regards, Greg.P.

Reply to
Greg.Procter

Zero 1 was introduced in the late 70s.

It was certainly "DCC" in that it was digital, but very much more limited in it's capabilities.

MBQ

Reply to
Man at B&Q

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