Re: latching relays

On 10/02/2025 23:42, Andrew Smallshaw wrote:

On 2025-02-10, Mike Scott <usenet.16@scottsonline.org.uk.invalid> wrote:

>
Thanks for the reply. I was considering complete units (like eg url
below (*)), which differ in operation. They take a pulse on a single
logic-level input, and flip-flop between states: my query is how to
reset from a random state to the power-up state.
>
The one you reference uses either reverse polarity or a 2nd coil to flip
and flop.

 [ https://www.amazon.co.uk/dp/B08LCTTR4Z/ ]
 Those are not conventional latching relays but standard one with
an external latching circuit.  The semantics oare defiferent.
latching relays use two coildand don't need power to maintain their
state.  The page tells you all you need to know, namely the relay
is not energised when power is first applied, so conductivity is
between NCx and COMx, switching to NOx and COMx on the first pulse.

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.

 Lack of proper data sheets is one of the reasons I'm not generally
a fan of commercial building block modules like this.
 

--
Mike Scott
Harlow, England