-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On Wed, Jun 20, 2007 at 08:57:22AM -0300, Gerhard Fiedler wrote:
> > If your communication is downstreams only a current-loop might be a nice
> > idea, although at 100 nodes the source voltage might be a bit high. 
> 
> Main consideration here is probably whether the public has access to the
> wires. The nice thing is that you don't have to deal with large currents.

The public very much has access to the wires, squirrels too. :)

> > There is no law that the lower voltage on the bus should be 0V: I can
> > imagine a but with for instance signalling levels 9V and 12V. 
> 
> Works for downstream only. You have some power to get rid of at the sender,
> though.

Hmm... such a system would nessesitate some sort of voltage regulator at
the slaves, unless the voltages were 5V and, say, 3V


What would the advantage be of such a system?

> > Alternatively signalling can be in HF, which can easily be added/removed
> > from the power line. 
> 
> Yes, RF or even audio (DTMF or modem type modulation).

So what would the node need to detect a HF signal? High-pass filter w/ a
capacitor?

> > 100 nodes might be too large for some setups, maybe split in separate
> > strings, or add repeaters.

Note that for installation reasons, the nodes really should be in a star
configuration, by strings do you mean strings of nodes?

> Good ideas. Add the possibility to do the communication in short intervals
> where you don't have power on the bus. 

What do you mean by the above?

- -- 
http://petertodd.org
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)

iD8DBQFGeVtV3bMhDbI9xWQRAhFEAKCBN6pm8GJDjYewXQFf1qEK5GofkQCgpdKN
pC3l9+qy1ShVrlbPNMu2VVs=
=x1Mh
-----END PGP SIGNATURE-----
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist