Path: ...!2.eu.feeder.erje.net!feeder.erje.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: John Robertson Newsgroups: sci.electronics.design Subject: Re: Replacing mechanical Latching Relays with dual coil relays... Date: Tue, 27 Aug 2024 07:06:03 -0700 Organization: A noiseless patient Spider Lines: 62 Message-ID: References: Reply-To: spam@flippers.com MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Tue, 27 Aug 2024 16:06:04 +0200 (CEST) Injection-Info: dont-email.me; posting-host="1cbff22a20f2030b22f28cc1e7896586"; logging-data="3167423"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1943TtBYjTPqW1ndQr3bEjsgy16hgKx7V0=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:aCCqZh0TkhJnqgTre7ebMYtpwK4= In-Reply-To: Content-Language: en-US, en-CA Bytes: 3497 On 2024-08-27 2:44 a.m., piglet wrote: > 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. >> >> Thanks, >> >> John :-#)# > > Millions of latching relays are still made. If the problem is under > voltages causing erratic activity I guess a driver with threshold detection > using LM339s or TL431s or whatever might be possible. Either to trigger > dual coil latch relays or single coil bipolar latch relays. The problem is switch noise. > > Can you give numbers, like correct coil voltage and the troublesome > incorrect voltages ? Correct coil voltage is 24VDC. Modern latching relays don't have a mechanical interlock - at least I haven't seen any - like the original Guardians. So if the microswitch to trip the relay is noisy then the modern latch relays go into a middle indeterminate state and then we get jammed gears - blown fuses. > > Something as simple as series SCR with zener anode to gate might be enough? > Yes, something like that may work, I'll have to post the schematic of a typical interlock relay when I have some time. Whatever is figured out has to not allow an indeterminate state. Thanks! John :-#)# -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."