Subject:
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Re: LDCC and Boosters
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Newsgroups:
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lugnet.trains
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Date:
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Tue, 24 Jun 2003 20:21:53 GMT
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Viewed:
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2796 times
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"Larry Pieniazek" wrote:
> In lugnet.trains, Mark Riley wrote:
> > "Tom Cook" wrote:
>
> > > I tried running two LDCC RCX bricks in parallel to gain more current. • It was
> > > not a success. I'm assuming phasing issues and conflicting commands • are to
> > > blame.
> >
> > Yes, the phase of the signals would have to be tightly in sync
> > to make this work.
>
> I'm wondering how you could possibly get the signals synced closely enough • for
> this to work without a physical cable connecting the two RCX internals
> (clocks??? I dunno). What is the cycle timing on these compared to • instruction
> clock rate? Even being off by 1% would, I would think, cause pretty good • surges
> of current, ne?
The CPU instructions can be anywhere from 1/8 to 1 microsecond
(or longer) in duration. Assuming you could sync up to within 1us,
you'd still be off by ~2% since the pulse duration for 1/2 of a
DCC "1" bit is 58us. Hooking up a pair of RCXs in parallel with
that kind of error would probably heat things up pretty quickly.
The test code I wrote to slave a second RCX using the sensor I
mentioned (in the other post) is only accurate to about ~8us because
of A/D limitations. It's probably not to DCC specifications
but the decoders I tested it with (DN121, DZ143) didn't seem
to mind. Improved code and/or an alternate sensor design
should be able to get it to specs.
Mark (who finds it kinda amusing to be geek'n in .trains).
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Message has 1 Reply:
 | | Re: LDCC and Boosters
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| (...) You'd have to look at the actual spec's for DCC, which are hosted by NMRA. I'm not sure what they actually call for- I know they are fairly tolarent of misdeeds. James (how nice to have someone geeking for us!) (23 years ago, 24-Jun-03, to lugnet.trains)
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Message is in Reply To:
| | Re: LDCC and Boosters
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| (...) I'm wondering how you could possibly get the signals synced closely enough for this to work without a physical cable connecting the two RCX internals (clocks??? I dunno). What is the cycle timing on these compared to instruction clock rate? (...) (23 years ago, 24-Jun-03, to lugnet.trains)
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