Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Don Y Newsgroups: sci.electronics.design Subject: Re: Replacing mechanical Latching Relays with dual coil relays... Date: Mon, 26 Aug 2024 14:09:26 -0700 Organization: A noiseless patient Spider Lines: 39 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Mon, 26 Aug 2024 23:09:29 +0200 (CEST) Injection-Info: dont-email.me; posting-host="4b6ad9061e36f01541b4056417d494de"; logging-data="2742159"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18nV6lv7hPcORT1X3TZQqnx" User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.2.2 Cancel-Lock: sha1:OaliitgVSMSm6h67te7On2nGjw8= In-Reply-To: Content-Language: en-US Bytes: 2986 On 8/26/2024 10:52 AM, John Robertson wrote: > Anyone have experience with dual coil latching relays? I'm trying to replace > old (1950s) Guardian latch relays as used in 1950s style jukeboxes with more > modern two coil latching relays but have had trouble with some relays going to > an indeterminate state if the power to the coil is  below optimum. > > What I actually need to do is a circuit that only allows the Latch/Reset coils > to trip when there is sufficient voltage and current available... > > This somewhat plays into the discussion on DC relay latching voltage thread and > I'm wondering if the Zener diode across the windings or in series with the > windings might help my design. > > As for the old original relays, the contacts are getting so pitted they can't > be saved and Guardian hasn't made this coil assy for decades. They don't turn > up on eBay either. You're not trying to be "genuine"... so, why dot replace the relay with a hybrid *circuit* that emulates a latching relay? [No idea what yours are like; I used to encounter them in pin setters ("ten pin") -- two coils mounted on a frame at right angles to each other. Each coil being a DPDT relay with their armatures mechanically interlocked. Nothing to prevent you from energizing BOTH coils except the actual design] Depending on the number (and form) of the contacts being used, you could design a little SR latch on a board, driving a single relay (to give you volt-free contacts) with the appropriate number (and form) of contacts. One possible complication would be if these were used to maintain state in a nonvolatile manner -- adding that to your circuit would require a nonvolatile store. Of course, the "easy" way is a tiny 6 pin MCU with a FET driving the relay... persistent state could be maintained in FLASH.