Re: latching relays

On Tue, 11 Feb 2025 19:04:20 GMT, David Higton <dave@davehigton.me.uk> wrote:

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

The one thing: You HAVE to prevent your control circuit (like Arduino) from sending spurious signals to the relay on power-up to
prevent unwanted/uncontrolled switching.  Known issue and solutions are on the internet i.e.
https://forum.arduino.cc/t/relay-turn-on-whenever-i-turn-on-arduino/644387

I would guess the Pi behaves in a similar way.