Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: David Higton <dave@davehigton.me.uk>
Newsgroups: comp.sys.raspberry-pi
Subject: Re: latching relays
Date: Tue, 11 Feb 2025 19:04:20 GMT
Organization: Home
Lines: 24
Message-ID: <929aa3ed5b.DaveMeUK@BeagleBoard-xM>
References: <vocfu0$14uka$1@dont-email.me> <icsjqjdoa37ucs9fnc1t9mfftb2b4ii6vs@4ax.com> <vod0uf$17r6d$1@dont-email.me> 
 <slrnvql3o2.si1.andrews@sdf.org> <vofpqt$1qm8g$1@dont-email.me>
Injection-Date: Tue, 11 Feb 2025 20:04:35 +0100 (CET)
Injection-Info: dont-email.me; posting-host="0417e93933fdc3a12c196188fe04dfe9";
	logging-data="2014741"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/pNuM6OQAnRSy6PWUXYnFkgqC+mMoVynQ="
User-Agent: Messenger-Pro/8.03 (MsgServe/8.01) (RISC-OS/5.31) NewsHound/v1.55
Cancel-Lock: sha1:458wAtVpnGCnB2w4TAItJdjsowM=
Bytes: 2063

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