Always the same problem...(sigh). The real issue is that the normal methods of doing this use a small amount of sensing current, like a voltage divider, ect. and/or they involve semiconductors such as transistors and IC's.
But I think I may know of a method that might work. It uses only very simple components, but it is a bit tricky. It involves using a sensitive polarity sensing reed relay with two N.O. point sets, one set closes with one coil polarity the other closes with the other polarity. The coil is connected to a set of (prob in this case good sized) capacitors, connected like a voltage divider with one caps end at pos the others at neg and the two tied together at the other ends. (If needed two reed relays could be connected to the caps if a single polarity sensitive relay of the correct type cannot be had cheaply.) This middle point where the caps are connected together is connected through a resistor (to control the charge/discharge time of the caps)to the coil of the reed relay. The other end of this coil is connected to the input single wire control. When the input goes either pos or neg one of the caps charges pos and the other charges neg. Current flows through the reed relays coils as the caps do this, causing one set or the other of the N.O. points to close depending on the polarity of the single wire input. The points of the reed relay supplies power to one or the other of either of two further relay coils. These are small relays that do not use much power in their coils, necessary since the reed relays points cannot handle much current. These relays points are used to control the coils of the latching relays. So the reed relay senses the polarity of power as the capacitors charge in response to the single wire input voltage, and one set or the other of its points close in response. These points in turn energize another set of relays that can handle enough power to drive the latching relays. With no power on the single input wire, no current flows anywhere. When there is voltage of either polarity, only one set of latching relays driver coils is energized at a time and so only one set latching relay coils are energized at a time. No current flows between any of these coils at any time. Again, when the single wire input 'floats' there is no current flow anywhere. I will send a schematic. -Ken _______________________________________________ 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
