----- Original Message -----
From: Eric T.
To: LIVE-ABOARD LIST
Sent: 7/28/2008 3:45:38 AM
Subject: [Liveaboard] Latching relay control
Eric - To control a latching relay with only 1 wire, use a dual coil relay.
Hook one end of one coil directly to 12 volts. Hook one end of the other coil
directly to ground. Connect the other ends of both coils through your 1 wire to
the center pole of a double throw, momentary contact switch.
Norm - As soon as you do this there will be 6 volts dropped across each of the
latching relay coils continuously. This will be a constant drain on the
system, not allowed.
Eric - Connect the other two poles to 12 volts and ground, respectively. Push
the switch one way and the relay latches in the on position. Push the switch
the other way and the relay latches in the off position. When the switch is
pressed the wrong way, nothing happens except a tiny bit of power is wasted.
Norm - As long as the latching relay will work properly with 6 volts across
each coil in the quiescent state this might work, but the constant drain is a
no-no.
Perhaps there is a semi-conductor, like a relief valve, that remains an open
with a voltage of say 9 volts across it, but closes to allow current to flow
when the 12 VDC appears (in either polarity) across it (and stays open as long
as the operating current flows) then opens again to isolate the two relay coils
when in the quiescent state.
Norm
S/V Bandersnatch
Lying Julington Creek
30 07.695N 081 38.484W
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