Subj : Re: latching relays To : David Higton From : Joe Date : Wed Feb 12 2025 14:57:11 On Tue, 11 Feb 2025 19:04:20 GMT, David Higton wrote: >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 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. --- SoupGate-Win32 v1.05 * Origin: Agency HUB, Dunedin - New Zealand | Fido<>Usenet Gateway (3:770/3) .