[TimP]

Planning to use the DCC power to build some electronics into various bits of rolling stock and I have a basic question perhaps some of you can help with...

When no control signals are present, am I right in assuming that the voltage applied to the rails has an alternating square waveform ... and if so what is its frequency ... is it simply the 50 Hz of the mains or something else ?

Then assuming that to be so, are the control signals synchronised to occur always at some fixed point in a power cycle ... such as the first positive rise ? In other words there must be some way of ensuring that control signals are not interrupted by power transitions.

Sorry spent a couple of hours on various websites and can't find this info anywhere.

Thanks

TimP

 

[Petal]

Have a look at this site for the basics
http://www.awrr.com/dccintro1.html
and
http://www.geocities.com/OzDCC/artpub.htm

 

[dwb]

Did you try the NMRA site (NMRA Standards page)?

David

 

[SPROGman]

QUOTE (TimP @ 4 Mar 2008, 19:11) <{POST_SNAPBACK}>Planning to use the DCC power to build some electronics into various bits of rolling stock and I have a basic question perhaps some of you can help with...
If all you want is power, then you can simply treat it as an AC waveform and fullwave rectify it. You should, however, use discrete high speed or schottky diodes and not a single package bridge rectifier. DCC is (for practical purposes) a square wave so the peak and RMS values are the same and you do not need large resevoir capacitors (just a small decoupler of a few uF). in fact, the charging current of a resevoir capacitor will play merry hell with the system and look like a short circuit to the command station at power on.
QUOTE When no control signals are present, am I right in assuming that the voltage applied to the rails has an alternating square waveform ... and if so what is its frequency ... is it simply the 50 Hz of the mains or something else ?
Control signals are always present. No, it's not 50Hz. Binary data is sent by varying the pulse width for 1 and 0 so there is no fixed frequency. A constant stream of 1s is nominally 8.6Khz and a constant stream of 0s is 5Khz (ignoring "zero stretching" used to drive DC locos).
QUOTE Then assuming that to be so, are the control signals synchronised to occur always at some fixed point in a power cycle ... such as the first positive rise ? In other words there must be some way of ensuring that control signals are not interrupted by power transitions.
The control signal *is* the power signal.

Andrew Crosland

 

[TimP]

Thanks to everyone for your help - esp SPROGman for your extra help - as yes am planning some reservoir capacitors.

If I get anything working I will stick up the designs and some photos.

TimP