From: none@nowhere.whereo   
      
   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.   
      
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    * Origin: you cannot sedate... all the things you hate (1:229/2)