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Serial+power over single coax cable

Started by Dejan January 19, 2005
I need to transfer ca. 5MB/S over coax cable, that should simultaneously
be used as a power supply line. There would be several stations, LAN-like...
Any suggestions?

- Dejan


Dejan wrote:

> I need to transfer ca. 5MB/S over coax cable, that should simultaneously > be used as a power supply line. There would be several stations, LAN-like... > Any suggestions?
Way easier with CAT5 and ethernet in a star configuration, essentially off-the-shelf. How much power? Do you mean bus topography?
Dejan wrote:
> > I need to transfer ca. 5MB/S over coax cable, that should > simultaneously be used as a power supply line. There would be > several stations, LAN-like... Any suggestions?
That would depend greatly on the power needs of each station, the total length of the line, the distribution of the stations, and the ohms/unit length of the cable used. Start by deciding if the cable will distribute the power at all, then consider multiplexing schemes. -- "If you want to post a followup via groups.google.com, don't use the broken "Reply" link at the bottom of the article. Click on "show options" at the top of the article, then click on the "Reply" at the bottom of the article headers." - Keith Thompson
"Jim Stewart" <jstewart@jkmicro.com> wrote in message
news:au-dnSH9IthoLHPcRVn-hA@omsoft.com..
> > Way easier with CAT5 and ethernet in a star > configuration, essentially off-the-shelf. > > How much power? Do you mean bus topography? >
It would be easier. However , the requirement is coax. At the moment, the power drain from the coax is not an issue. Yes - it's a bus topology. Also, it would be a master-slave system, so there's no need for colision detection. Slaves only respond when asked by master, one at a time. Generally, what modulation types are preferred? - Dejan
On Wed, 19 Jan 2005 19:49:05 +0100, "Dejan" <no@spam.com> wrote:

>I need to transfer ca. 5MB/S over coax cable, that should simultaneously >be used as a power supply line. There would be several stations, LAN-like... >Any suggestions?
Some form of Manchester coding is often used, when you want to get rid of DC-components, which also would permit separating the DC power and the signal. As a coaxial cable has a large bandwidth, you could even send it on some RF carrier (say 30 MHz) and run FSK or even amplitude modulation. However, if this is done, you have to be careful about the line termination, the station branch lengths and the minimum distance between the branches. Paul
Jim Stewart wrote:
> Dejan wrote: > >> I need to transfer ca. 5MB/S over coax cable, that should simultaneously >> be used as a power supply line. There would be several stations, >> LAN-like... >> Any suggestions? > > > Way easier with CAT5 and ethernet in a star > configuration, essentially off-the-shelf.
Just as sidenote : coax can carry much more power. Especially when I think about RG214 and such, doing 5kVrms Rene -- Ing.Buero R.Tschaggelar - http://www.ibrtses.com & commercial newsgroups - http://www.talkto.net
Dejan wrote:

> I need to transfer ca. 5MB/S over coax cable, that should simultaneously > be used as a power supply line. There would be several stations, LAN-like... > Any suggestions?
Yes, take a DDS that does some FSK or PSK modulation for you. Coupling onto the cable is done with caps holding the DC voltage. For the modulation frequency you need correct AC termination, meaning a 50 Ohm behind the caps. Rene -- Ing.Buero R.Tschaggelar - http://www.ibrtses.com & commercial newsgroups - http://www.talkto.net
Dejan wrote:
> > It would be easier. However , the requirement is coax. At the moment, the > power drain from > the coax is not an issue. > > Yes - it's a bus topology. Also, it would be a master-slave system, so > there's no need for > colision detection. Slaves only respond when asked by master, one at a > time. > > Generally, what modulation types are preferred? > > - Dejan
Over what distance? Is it 5M bytes or 5M bits?
Paul Keinanen wrote:

> On Wed, 19 Jan 2005 19:49:05 +0100, "Dejan" <no@spam.com> wrote: > > >>I need to transfer ca. 5MB/S over coax cable, that should simultaneously >>be used as a power supply line. There would be several stations, LAN-like... >>Any suggestions? > > > Some form of Manchester coding is often used, when you want to get rid > of DC-components, which also would permit separating the DC power and > the signal. > > As a coaxial cable has a large bandwidth, you could even send it on > some RF carrier (say 30 MHz) and run FSK or even amplitude modulation. > However, if this is done, you have to be careful about the line > termination, the station branch lengths and the minimum distance > between the branches.
You might be able to make it work with cable modems.
CBFalconer wrote:

> Dejan wrote: >> >> I need to transfer ca. 5MB/S over coax cable, that should >> simultaneously be used as a power supply line. There would be >> several stations, LAN-like... Any suggestions? > > That would depend greatly on the power needs of each station, the > total length of the line, the distribution of the stations, and the > ohms/unit length of the cable used. > > Start by deciding if the cable will distribute the power at all, > then consider multiplexing schemes.
The main problems in this will be the node PADs where the power and the signals will be separated. The consideration here, of course, is avoiding any form of ground-loop that may disrupt the proper processing of the network signals. I predict that you will need to sit down with SPICE and run plenty of simulations on your candidate node PADs. Don't forget to model the coaxial lengths between systems as well as the nodes. -- ******************************************************************** Paul E. Bennett ....................<email://peb@a...> Forth based HIDECS Consultancy .....<http://www.amleth.demon.co.uk/> Mob: +44 (0)7811-639972 .........NOW AVAILABLE:- HIDECS COURSE...... Tel: +44 (0)1235-811095 .... see http://www.feabhas.com for details. Going Forth Safely ..... EBA. www.electric-boat-association.org.uk.. ********************************************************************