DIYbanter - View Single Post

Chris

On 16/05/2011 12:54, wrote:
On May 16, 2:06 am, Wolf wrote:
On 15/05/2011 4:16 PM, wrote:

Wolf wrote:

[snip]

he DCC decoders convert rail power (14-18V, 50/60HZ)
If you can't even the basics right about DCC, why bother posting?

[snip]

AIUI, DCC puts a digital signal on top of an AC propulsion current.

No, the "propulsion current" and the digital signal are one and the
same.

The
latter is rectified to sine wave DC by the decoder,

The DCC track voltage is a square wave digital signal and is rectified
to DC in the decoder.

and is in turn
chopped to provide average voltages below the maximum, thus controlling
the speed of the locomotive. If this is incorrect, please elucidate.

That bit is correct.

The signal is delivered to the locomotive in the form of data packets,
whose format is specified in NMRA Standard S-9.1. This standard also
indicates that the propulsion current is AC, Vmax between 14 and 18V RMS.

S-9.1 is the electrical standard. The voltage limits depend on other
non-DCC scale specific standards.

Basic data packets are defined in S-9.2.

My recollection of the propulsion current and the signal current
relationship is that the former is "ordinary" AC, ie, 50/60Hz,

NO. "AC" does not mean 50 or 60Hz other than in the very limited
definition of household mains.

depending
on country,

The country is irrelevant.

and the latter a high frequency, whose value I've probably
got wrong, because I wrote from memory. Kindly correct and elucidate my
errors.

You've hinted at the NMRA specs, why not read them for yourself?

The system you are describing is more akin to Hornby's Zero One, long
since deprecated.

MBQ

Its not rectified at all its transformed into PWM feed to the motor the
frequency can be varied on some decoders so that they can be tuned to
particular motor types. Works the same way as DC PWM controllers.

--
Chris