Re: Replacing mechanical Latching Relays with dual coil relays...

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.