Paul E. Bennett wrote:> 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.Separating the power from the signal will not be that difficult. Get the signal through caps and the power through inductivities. On both ends. For the bidirectional signal, a rotator separates the waves in either direction. Their implementation depends on the frequency range. Rene -- Ing.Buero R.Tschaggelar - http://www.ibrtses.com & commercial newsgroups - http://www.talkto.net
Serial+power over single coax cable
Started by ●January 19, 2005
Reply by ●January 20, 20052005-01-20
Reply by ●January 20, 20052005-01-20
Hi Dejan,>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? > >Power should not be a big deal with coax but make sure it's all fused and protected. As to data I'd modulate it onto a carrier, probably FM if it needs to be cheap. I'd pick a band where the likelyhood of interference is lowest, preferably ISM like the 900MHz band. Just in case somebody makes a mistake, a connector shell comes loose etc. That has the other advantage that you'll be able to obtain cheap HW. You may then want to go with whatever modulation scheme the popular chipsets use. You could probably even go 2.4GHz where HW is really cheap but that is a challenge for longer cable runs and for the distribution and router circuitry. Just resist the temptation to leave it all at baseband. That can cause serious susceptibility. I have seen lots of grief in non-twisted baseband data cables, such as 'it all works unless somebody uses the elevator...'. Regards, Joerg http://www.analogconsultants.com
Reply by ●January 20, 20052005-01-20
"Paul E. Bennett" wrote:> 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.No, the first problem is to find out if the system has any chance of working. To illustrate, lets assume the cable is RG58U, 100 meters long, with a station every 10 meters requiring 12V at 1 Amp, adding up to 10 Amps total. Now I don't know that the ohms / meter are for RG58U, but I seriously doubt that it can carry the net current to deliver that power, and even if it does the ohmic drops will be such that local regulators are needed, etc. etc. -- "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
Reply by ●January 21, 20052005-01-21
In article <41F05DA4.2AB8DB97@yahoo.com>, cbfalconer@yahoo.com says...> No, the first problem is to find out if the system has any chance > of working. To illustrate, lets assume the cable is RG58U, 100 > meters long, with a station every 10 meters requiring 12V at 1 Amp, > adding up to 10 Amps total. Now I don't know that the ohms / meter > are for RG58U, but I seriously doubt that it can carry the net > current to deliver that power, and even if it does the ohmic drops > will be such that local regulators are needed, etc. etc.According to http://www.elpa.lt/eng/cables/coaxial/490503.html 34 Ohms/Km inner conductor, 17 Ohms/Km outer conductor So 5.1 Ohms round trip, or a 51V drop. Unless I dropped a decimal point somewhere. Of course most of the current doesn't go the full distance but even at 1A there is a 5V dropand that estimate would be too optimistic. No indication there of when you run into heating problems though. Robert
Reply by ●January 21, 20052005-01-21
CBFalconer wrote:> "Paul E. Bennett" wrote: > >>CBFalconer wrote:>>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. > > > No, the first problem is to find out if the system has any chance > of working. To illustrate, lets assume the cable is RG58U, 100 > meters long, with a station every 10 meters requiring 12V at 1 Amp, > adding up to 10 Amps total. Now I don't know that the ohms / meter > are for RG58U, but I seriously doubt that it can carry the net > current to deliver that power, and even if it does the ohmic drops > will be such that local regulators are needed, etc. etc.RG58 is good for at least 500V, spec'ed for 2.5kV operating. So this should leave some room for a switcher. Rene -- Ing.Buero R.Tschaggelar - http://www.ibrtses.com & commercial newsgroups - http://www.talkto.net
Reply by ●January 21, 20052005-01-21
R Adsett wrote:> In article <41F05DA4.2AB8DB97@yahoo.com>, cbfalconer@yahoo.com says... > >> No, the first problem is to find out if the system has any chance >> of working. To illustrate, lets assume the cable is RG58U, 100 >> meters long, with a station every 10 meters requiring 12V at 1 Amp, >> adding up to 10 Amps total. Now I don't know that the ohms / meter >> are for RG58U, but I seriously doubt that it can carry the net >> current to deliver that power, and even if it does the ohmic drops >> will be such that local regulators are needed, etc. etc. > > According to http://www.elpa.lt/eng/cables/coaxial/490503.html 34 > Ohms/Km inner conductor, 17 Ohms/Km outer conductor > > So 5.1 Ohms round trip, or a 51V drop. Unless I dropped a decimal > point somewhere. Of course most of the current doesn't go the full > distance but even at 1A there is a 5V dropand that estimate would > be too optimistic.Exactly. Even if the current per station is cut to 0.1 A the system is obviously hairy. Any reasonable use would need local DC/DC converters and regulators. By this time you probably want to increase the supply voltage (on the coax) to reduce current and mitigate ohmic losses. In any reasonable world that voltage is limited to 48 V for safety reasons. Of course if the coax run is only 10 meters total, the numbers change. But I don't think such a physically small overall system warrants the complications of supplying power over the cable. Once the OP settles these fundamental questions he can decide on actual means of multiplexing data and power. -- "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
Reply by ●January 21, 20052005-01-21
Rene Tschaggelar <none@none.net> wrote:> RG58 is good for at least 500V, spec'ed for 2.5kV operating.The cable may be. But I hope you're aware that in a lot of countries, to go beyond around 48V, you'll need board-certified personnel to install any cable routinely carrying that kind of voltage, aren't you? Remember: legally, anything beyond about 48 volts is considered dangerous, experts-only "high voltage". Anybody without formal certification ever having been allowed to fiddle with such a system is thus considered gross neglect of duties, and loses all insurance protection. -- Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de) Even if all the snow were burnt, ashes would remain.
Reply by ●January 21, 20052005-01-21
Hans-Bernhard Broeker wrote:> Rene Tschaggelar <none@none.net> wrote: > > >>RG58 is good for at least 500V, spec'ed for 2.5kV operating. > > > The cable may be. But I hope you're aware that in a lot of countries, > to go beyond around 48V, you'll need board-certified personnel to > install any cable routinely carrying that kind of voltage, aren't you? > > Remember: legally, anything beyond about 48 volts is considered > dangerous, experts-only "high voltage". Anybody without formal > certification ever having been allowed to fiddle with such a system is > thus considered gross neglect of duties, and loses all insurance > protection.Is that the case of amateur radio operators as well? The RF voltages in a typical amateur radio antenna lead could easily be in the 100's of volts.
Reply by ●January 21, 20052005-01-21
Jim Stewart wrote:> Hans-Bernhard Broeker wrote: >> Rene Tschaggelar <none@none.net> wrote: >> >> >>>RG58 is good for at least 500V, spec'ed for 2.5kV operating. >> >> >> The cable may be. But I hope you're aware that in a lot of countries, >> to go beyond around 48V, you'll need board-certified personnel to >> install any cable routinely carrying that kind of voltage, aren't you? >> >> Remember: legally, anything beyond about 48 volts is considered >> dangerous, experts-only "high voltage". Anybody without formal >> certification ever having been allowed to fiddle with such a system is >> thus considered gross neglect of duties, and loses all insurance >> protection. > > Is that the case of amateur radio operators as > well? The RF voltages in a typical amateur radio > antenna lead could easily be in the 100's of > volts.I think the legal situation appliesonly to products not persons. if a device uses voltages only below 48V (so called safety extra low) it makes it easier for it to gain safety certification no matter what side of the pond you are on. Using higher voltages requires measures to ensure users cannot be harmed by them before safety certification is granted - applies to most all domestic mains operated appliances. None of this applies to anything you make yourself at home. Ian -- Ian Bell
Reply by ●January 21, 20052005-01-21
Ian Bell wrote:> Jim Stewart wrote: > > >>Hans-Bernhard Broeker wrote: >> >>>Rene Tschaggelar <none@none.net> wrote: >>> >>> >>> >>>>RG58 is good for at least 500V, spec'ed for 2.5kV operating. >>> >>> >>>The cable may be. But I hope you're aware that in a lot of countries, >>>to go beyond around 48V, you'll need board-certified personnel to >>>install any cable routinely carrying that kind of voltage, aren't you? >>> >>>Remember: legally, anything beyond about 48 volts is considered >>>dangerous, experts-only "high voltage". Anybody without formal >>>certification ever having been allowed to fiddle with such a system is >>>thus considered gross neglect of duties, and loses all insurance >>>protection. >> >>Is that the case of amateur radio operators as >>well? The RF voltages in a typical amateur radio >>antenna lead could easily be in the 100's of >>volts. > > > I think the legal situation appliesonly to products not persons. if a > device uses voltages only below 48V (so called safety extra low) it makes > it easier for it to gain safety certification no matter what side of the > pond you are on. Using higher voltages requires measures to ensure users > cannot be harmed by them before safety certification is granted - applies > to most all domestic mains operated appliances.My question was a bit of a troll for Hans-Bernhard. The legal issues vary widely from place to place and I am curious how amateur radio operators deal with the regulations in Germany. In my city, the saying is "you need a building permit to drive a nail". OTOH, they are extremely helpful with homeowners that do the work themselves. I drew up plans for a 240 volt, 50 ampere subpanel in my garage, had the chief building inspector sign off the drawing, did the work, got it inspected and signed off by the city for about $40 in fees. The last city I lived in *required* all electrical work to be done by a licensed electrician.
