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PID: SoupGate-Win32 v1.05
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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