Hmmm... Thanks, but: About 2 minutes after hitting SEND I thought I realized that setup would need a 2-coil relay, not a 1-coil... I'll re-read and muddle some more...
I think Ken's idea of a bridge rectifier (I _think_ that's what he's saying) might work; I think you'd need access to all four poles of the rectifier, though, and it would have a tiny idle current since it connects the coils together and one coil is high and one low. Since rectifiers are commodities that might be the best way - cheap coils and cheap packaged electronics. If you made up the rectifier or otherwise had access to insert the coil _into_ the bridge, you could probably use a 1-coil relay. My little mind has reached grid lock but maybe some pencil work later will clarify things. You'd better paste an archival grade schematic and a few lines of explanation to the inside of the button box, though! Rufus > ----- Original Message ----- > From: "Norm of Bandersnatch" <[EMAIL PROTECTED]> > To: [email protected] > Subject: Re: [Liveaboard] 1 wire relay cntl - fr. 12 VDC buss > Date: Mon, 28 Jul 2008 11:01:41 -0400 > > > > Well done Rufus, I think your idea may work. I am not on the boat now so > I can't rig up a breadboard to try it out, but the idea looks good. > > The only drawback is the need to have a double pole latching relay. I > don't have a source for those yet. > > The other down side is that it won't work with the latching relay I want to > use. I have a large single coil type SPST latching relay (where the state > changes depending on the current flow direction through a single coil) I > want to use as a house/start battery crossover switch for getting some > extra juice for starting the main engine when needed. I thought of using a > large starting solenoid type relay but I am concerned that if the batteries > are low the relay might drop out when I hit the starter. > > As for just running two wires - most of the control wires I have are in > multiple wire cables that connect centers of activity such as the engine > room and the instrument panel. Many of the conductors are in use and there > are a few spares. I wish, through clever design, to use these wires as > economically as possible to allow for future expansion, thus the desire to > use one wire where normally two would be used. > > In addition to operating the big SPST crossover latching relay using one > wire, I would like to send the engine overheat signal and the oil pressure > low signal from the engine room to the instrument panel over one wire using > the same philosophy, that neutral condition would be a floating wire, one > condition a positive 12 VDC and the other condition a Ground. > > There's gotta be a simple, elegant way to do these things. > > Norm > S/V Bandersnatch > Lying Julington Creek > 30 07.695N 081 38.484W > > > > [Original Message] > > From: Rufus Laggren <[EMAIL PROTECTED]> > > To: <[email protected]> > > Date: 7/27/2008 6:51:51 PM > > Subject: Re: [Liveaboard] 1 wire relay cntl - fr. 12 VDC buss > > > > Well, I considered a "floater" at first but lost it somewhere in my > rigorous thought process...<g> Now I think about it some more if you used > a single-coil relay, wouldn't a DPDT relay work with the floating signal on > one coil terminal with the other coil terminal either grounded or hotted by > the extra pole on the relay? That'd solve the oscillator problem, also; for > any particular state the signal line would only carry current until it > threw the relay - after that both ends would be at the same potential. > > > > The coil might need a little help to complete the latching process after > the relay drops one side of its circuit - a hefty capacitor on the > non-signal coil terminal? But maybe it'd work without it. Don't know what > the trade-off between installing a good capacitor and installing a 2nd > signal line looks like. I'd say the 2nd wire makes more sense because you > lose the capacitor (and/or any other shaping circuitry) and you get to use > SPST relays. I guess you could use solid state to flip the coil polarity at > the relay but that would mean more futzing and also some kind of phantom > load. A single twisted pair for the signal line is almost as simple a one > wire. > > > > Rufus > > > > > ----- Original Message ----- > > > From: "Norm of Bandersnatch" <[EMAIL PROTECTED]> > > > To: [email protected] > > > Subject: Re: [Liveaboard] 1 wire relay cntl - fr. 12 VDC buss > > > Date: Sat, 26 Jul 2008 21:37:41 -0400 > > > > > > Notice I said "(system ground and system 12 VDC is > > available at both the > > > switch(s) and the relay)". > > > > I imagine a system where the single line is normally floating with > nothing > > > on it. The control switch(s) would put the control line to 12 VDC or > > > Ground when activated. Somehow at the latching realy the realy would > flip > > > from one state to the other depending whether the control line went to > 12 > > > VDC or to Ground. To save juice, no current should flow when the > control > > > switch(s) are not pressed. > > > > > > -- Be Yourself @ mail.com! > > Choose From 200+ Email Addresses > > Get a Free Account at www.mail.com > > > > > > _______________________________________________ > > Liveaboard mailing list > > [email protected] > > To adjust your membership settings over the web > http://www.liveaboardnow.org/mailman/listinfo/liveaboard > > To subscribe send an email to [EMAIL PROTECTED] > > > > To unsubscribe send an email to [EMAIL PROTECTED] > > The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ > > > > To search the archives > http://www.mail-archive.com/[email protected] > > > > The Mailman Users Guide can be found here > http://www.gnu.org/software/mailman/mailman-member/index.html > > > _______________________________________________ > Liveaboard mailing list > [email protected] > To adjust your membership settings over the web > http://www.liveaboardnow.org/mailman/listinfo/liveaboard > To subscribe send an email to [EMAIL PROTECTED] > > To unsubscribe send an email to [EMAIL PROTECTED] > The archives are at http://www.liveaboardnow.org/pipermail/liveaboard/ > > To search the archives > http://www.mail-archive.com/[email protected] > > The Mailman Users Guide can be found here > http://www.gnu.org/software/mailman/mailman-member/index.html > -- Be Yourself @ mail.com! 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