Replacing mechanical Latching Relays with dual coil relays...

[John Robertson]

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 :-#)#

[John Robertson]

Post by John Robertson
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 :-#)#

Oh, and Guardian called these latching relays INTERLOCKING RELAYs and
they look like this (this is a 120VAC coil version):

Loading Image...

Loading Image...

John :-#)#


--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
#7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
[phone] (Pinballs, Jukes, Video Games)
www.flippers.com
"Old

[Don Y]

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.

[John Robertson]

Post by Don Y

Post by John Robertson
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]

Yes, this sounds the same.

Post by Don Y
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.

There are two DPDT relays that change state together. 8A non-inductive
at 24VDC contacts.

Post by Don Y
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.

Ah, yes these MUST be non-volatile. The relay must stay set/reset until
the mechanical operation resets it, otherwise fuses blow after the gears
jam. Power interruptions can't change that state...

Post by Don Y
Of course, the "easy" way is a tiny 6 pin MCU with a FET driving the
relay...  persistent state could be maintained in FLASH.

Now you are just getting fancy! (ducking)

John :-#(#

--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
#7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
[phone] (Pinballs, Jukes, Video Games)
www.flippers.com
"O

[Don Y]

Post by Don Y
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.

There are two DPDT relays that change state together. 8A non-inductive at 24VDC
contacts.

But, one *passively* changes state (its restoring spring is allowed to move
the armature) while the other actively changes state (its armature moving
because of the magnetic force created in the energized coil)

Post by Don Y
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.

Ah, yes these MUST be non-volatile. The relay must stay set/reset until the
mechanical operation resets it, otherwise fuses blow after the gears jam. Power
interruptions can't change that state...

<frown>

Post by Don Y
Of course, the "easy" way is a tiny 6 pin MCU with a FET driving the
relay...  persistent state could be maintained in FLASH.

Now you are just getting fancy! (ducking)

No, it was just the easiest way to get the nonvolatile support.

Without the MCU, a cross-coupled NAND (SR latch) could be driven by the
two "low side" coil controls: pull line A to ground to engage coil A
and release coil B; pull line B to ground to engage coil B and
release coil A. A pullup and clamp to V(logic) for each input.
The output of the latch driving a FET or BJT to energize the
*4PDT* relay (with two poles wired in the NO configuration and
the other two in the NC configuration to mimic the two relays
being in different states).

If these have to persist in the absence of power (assuming you can
tolerate the brief delay while the relay reenergizes to resume its
previous state when power reappears), then you need something that
will ALWAYS remember.

You likely don't want to have to put coin cells on each such board
to preserve the state of the SR latch. The MCU made this a bit easier
as you could (hopefully) just set aside a piece of FLASH to store
state (taking into account wear)

[Phil Hobbs]

Post by John Robertson

Post by Don Y

Post by John Robertson
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]

Yes, this sounds the same.

Post by Don Y
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.

There are two DPDT relays that change state together. 8A non-inductive
at 24VDC contacts.

Post by Don Y
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.

Ah, yes these MUST be non-volatile. The relay must stay set/reset until
the mechanical operation resets it, otherwise fuses blow after the gears
jam. Power interruptions can't change that state...

Post by Don Y
Of course, the "easy" way is a tiny 6 pin MCU with a FET driving the
relay...  persistent state could be maintained in FLASH.

Now you are just getting fancy! (ducking)
John :-#(#

I’d be cautious about any solution that separates the physical state of the
switch from the logical state.

How about a nice small latching relay controlling a triac or SSR? You can
do the UVLO function with a MAX809 or something like that to gate the
supply to the relay coil.

Cheers

Phil Hobbs

[john larkin]

On Tue, 27 Aug 2024 14:02:37 -0000 (UTC), Phil Hobbs

Post by John Robertson

Post by Don Y

Post by John Robertson
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]

Yes, this sounds the same.

Post by Don Y
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.

There are two DPDT relays that change state together. 8A non-inductive
at 24VDC contacts.

Post by Don Y
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.

Ah, yes these MUST be non-volatile. The relay must stay set/reset until
the mechanical operation resets it, otherwise fuses blow after the gears
jam. Power interruptions can't change that state...

Post by Don Y
Of course, the "easy" way is a tiny 6 pin MCU with a FET driving the
relay...  persistent state could be maintained in FLASH.

Now you are just getting fancy! (ducking)
John :-#(#

I’d be cautious about any solution that separates the physical state of the
switch from the logical state.
How about a nice small latching relay controlling a triac or SSR? You can
do the UVLO function with a MAX809 or something like that to gate the
supply to the relay coil.

Or a small latching relay controlling a big ole relay?

We like the

FUJITSU FTR-B3GB4.5Z-B10

[John Robertson]

Post by john larkin
On Tue, 27 Aug 2024 14:02:37 -0000 (UTC), Phil Hobbs

Post by Phil Hobbs

Post by John Robertson

Post by Don Y

Post by John Robertson
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]

Yes, this sounds the same.

Post by Don Y
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.

There are two DPDT relays that change state together. 8A non-inductive
at 24VDC contacts.

Post by Don Y
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.

Ah, yes these MUST be non-volatile. The relay must stay set/reset until
the mechanical operation resets it, otherwise fuses blow after the gears
jam. Power interruptions can't change that state...

Post by Don Y
Of course, the "easy" way is a tiny 6 pin MCU with a FET driving the
relay...  persistent state could be maintained in FLASH.

Now you are just getting fancy! (ducking)
John :-#(#

I’d be cautious about any solution that separates the physical state of the
switch from the logical state.
How about a nice small latching relay controlling a triac or SSR? You can
do the UVLO function with a MAX809 or something like that to gate the
supply to the relay coil.

Or a small latching relay controlling a big ole relay?
We like the
FUJITSU FTR-B3GB4.5Z-B10

Interesting that you reverse the coil polarity to release the single coil.

Gives me other ideas on solving the problem - use a small (2A contacts)
dual coil latching relay to drive a bigger relay. The small relay won't
be bothered as much by switch noise as the current required is much less
so is unlikely to get into an illegal state. Will read the product
literature on these and see what comes up as a good unit.

Like I don't have enough projects!

John :-#)#




--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd.
#7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
[phone] (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pi

[john larkin]

Post by John Robertson

Post by john larkin
On Tue, 27 Aug 2024 14:02:37 -0000 (UTC), Phil Hobbs

Post by John Robertson

Post by Don Y

Post by John Robertson
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]

Yes, this sounds the same.

Post by Don Y
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.

There are two DPDT relays that change state together. 8A non-inductive
at 24VDC contacts.

Post by Don Y
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.

Ah, yes these MUST be non-volatile. The relay must stay set/reset until
the mechanical operation resets it, otherwise fuses blow after the gears
jam. Power interruptions can't change that state...

Post by Don Y
Of course, the "easy" way is a tiny 6 pin MCU with a FET driving the
relay...  persistent state could be maintained in FLASH.

Now you are just getting fancy! (ducking)
John :-#(#

I’d be cautious about any solution that separates the physical state of the
switch from the logical state.
How about a nice small latching relay controlling a triac or SSR? You can
do the UVLO function with a MAX809 or something like that to gate the
supply to the relay coil.

Or a small latching relay controlling a big ole relay?
We like the
FUJITSU FTR-B3GB4.5Z-B10

Interesting that you reverse the coil polarity to release the single coil.

We use a fiendishly clever dual NOR gate circuit to drive these. It
takes basically one wire per relay from our uP or FPGA.

[legg]

Post by John Robertson

Post by john larkin
On Tue, 27 Aug 2024 14:02:37 -0000 (UTC), Phil Hobbs

Post by John Robertson

Post by Don Y

Post by John Robertson
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]

Yes, this sounds the same.

Post by Don Y
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.

There are two DPDT relays that change state together. 8A non-inductive
at 24VDC contacts.

Post by Don Y
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.

Ah, yes these MUST be non-volatile. The relay must stay set/reset until
the mechanical operation resets it, otherwise fuses blow after the gears
jam. Power interruptions can't change that state...

Post by Don Y
Of course, the "easy" way is a tiny 6 pin MCU with a FET driving the
relay...  persistent state could be maintained in FLASH.

Now you are just getting fancy! (ducking)
John :-#(#

I’d be cautious about any solution that separates the physical state of the
switch from the logical state.
How about a nice small latching relay controlling a triac or SSR? You can
do the UVLO function with a MAX809 or something like that to gate the
supply to the relay coil.

Or a small latching relay controlling a big ole relay?
We like the
FUJITSU FTR-B3GB4.5Z-B10

Interesting that you reverse the coil polarity to release the single coil.
Gives me other ideas on solving the problem - use a small (2A contacts)
dual coil latching relay to drive a bigger relay. The small relay won't
be bothered as much by switch noise as the current required is much less
so is unlikely to get into an illegal state. Will read the product
literature on these and see what comes up as a good unit.
Like I don't have enough projects!
John :-#)#

Depends on whether simply 'remembering' last state is as
good as holding it, during power loss.

RL

[john larkin]

On Mon, 26 Aug 2024 14:09:26 -0700, Don Y

Post by Don Y

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.

A little cmos flipflop circuit and a Tadiran lithium battery or a
supercap would work too.

[Liz Tuddenham]

Post by John Robertson
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.

Two opposed solenoids and an arm on the spindle of a rotary switch.

[Jasen Betts]

Post by Liz Tuddenham

Post by John Robertson
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.

Two opposed solenoids and an arm on the spindle of a rotary switch.

Or on an bank of opposed microswitches. I've seen that done except
the solenoide were a telephone ringer hammer driver.

[Phil Hobbs]

Post by Jasen Betts

Post by Liz Tuddenham

Post by John Robertson
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.

Two opposed solenoids and an arm on the spindle of a rotary switch.

Or on an bank of opposed microswitches. I've seen that done except
the solenoide were a telephone ringer hammer driver.

The rated lifetime of your average switch is a small fraction of your
average relay’s, even if you don’t abuse it like that.

Some microswitches are better, but still not the 1E7 of a good relay iirc.

Cheers

Phil Hobbs

[piglet]

Post by John Robertson
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.

Can you give numbers, like correct coil voltage and the troublesome
incorrect voltages ?

Something as simple as series SCR with zener anode to gate might be enough?

[John Robertson]

Post by piglet

Post by John Robertson
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.

Post by piglet
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.

Post by piglet
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 :-#)#

[Joe Gwinn]

Post by John Robertson

Post by piglet

Post by John Robertson
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.

Post by piglet
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.

Post by piglet
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.

There is a large literature on electronic designs for interlocking
safety-critical functions, like firing a rocket or detonating a bomb.
This literature can be a source of circuit ideas and hazards to be
addressed.

Joe Gwinn