Re: Simple data bus over DC Power Wires

From: Fred Bloggs (nospam_at_nospam.com)
Date: 06/22/04 

Date: Tue, 22 Jun 2004 13:56:38 GMT

Tony Williams wrote:
> In article <40D44990.30203@nospam.com>,
> Fred Bloggs <nospam@nospam.com> wrote:
>
>
>>There just may be:
>>http://www.interfacebus.com/Design_Connector_Field_Buses.html
>
>
> I looked there, but couldn't see anything related
> to multi-channel control over the DC supply wires.
>
> I have a pal who (in later life) is resurrecting
> his interest in model railways. Apparently there
> is now some reasonably standardised method of
> multi-device control via the DC supply through
> the rails. Trains, points and signals can all be
> controlled via one DC supply. It is supposed to
> be popular in the US model engineering market,
> but he hasn't been able to find out any technical
> details yet.
>

I don't think that DCC is suitable because it looks they reverse the
polarity on the rails or some crazy thing. The Siemens ASI seems to be
it. It uses a simple unshielded two wire data+power cable and the
network can be up to 64 slaves each of which can be multiple I/O. Noise
immunity is achieved by superimposing a narrowband sinewave that is
modulated by something called APM= Alternate Pulse Modulation- of just
exactly what-phase, amplitude, or something else-I don't know, but the
slave receivers require crystal timebases. The ASI has been around for
10 years now so that it is well-developed and supported- you can tie it
into almost any other industrial control bus, or PCI, or VME, or
whatever- and there are plenty of chipsets available for building a
product from scratch too. It has quite a bit of protocol overhead so
that custom development would not make sense unless you're building a
compatible product for market- an in-house actuator control bus should
use readily available off-the-shelf modules from any one of dozens of
manufacturers.