Subj : Re: latching relays
To   : Mike Scott
From : David Higton
Date : Tue Feb 11 2025 19:04:20

In message <vofpqt$1qm8g$1@dont-email.me>
          Mike Scott <usenet.16@scottsonline.org.uk.invalid> 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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