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REPLYADDR dave@davehigton.me.uk
REPLYTO 3:770/3.0 UUCP
MSGID: <929aa3ed5b.DaveMeUK@BeagleBoard-xM> 8dd6c46f
REPLY:  fc56a665
PID: SoupGate-Win32 v1.05
In message 
          Mike Scott  wrote:

> OK, I get it. I'm after something that'll retain the same setting for
> extended periods, hence the desire for a latching relay to keep power
> dissipation down. Indeed, it does look as though what I've been looking  at
> is a normal relay plus a flip-flop - not what I want, and I think  you've
> saved me from a bad mistake.
>
> Not wanting to mess with relay driver circuitry, I've found something
> that's definitely latching at PiHut (I hope!!). Pricey, but complete
> modules don't seem available otherwise.
>
> Thanks to all for commenting.

Look at the Hongfa HFD2 data sheet.  The range includes single side
stable (i.e. an "ordinary" relay), 1 coil latching, and 2 coils
laching, and shows how to connect and how to energise to get latching
relays of either type into the state you want.

The latching relays are the real thing; they retain state indefinitely,
without power, after being set to either state.

David

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