many relay drivers...

J

John Larkin

Guest
https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?
 
John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?
Click to expand...

TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
 
On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs
Click to expand...

I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.

Dropout would be fast!
 
John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:
On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs

I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.

Dropout would be fast!
Click to expand...

So use a couple of SC-70s instead. (It needs to be a bidirectional TVS.)

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
 
On Mon, 24 Jul 2023 18:15:44 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs

I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.

Dropout would be fast!
Click to expand...

Yes, the high voltage transistor can do the work as long a it can take
the energy. I do that too when I need turn-off to be fast.
Otherwise, I just use a cache diode across the coil.

The circulating current with a regular diode will slow the switch off
but quite a lot. Sometimes it\'s ok but sometimes, like with line
connected inverter/charger, we need it to turn off in a couple of ms
rather than 10 ms or so.

boB
 
On Mon, 24 Jul 2023 18:15:44 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs

I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.

Dropout would be fast!
Click to expand...

This is the guts of a TE PCJ, 7x20 mm SPST 5 amps.

https://www.dropbox.com/scl/fi/efgmcu53iw934yl5clpv4/TE_PCJ.jpg?rlkey=bcq6l39gaq7rrg7p4yuqbp2nj&raw=1

I was a little concerned about mag field interaction so now I know
where the coil is. I\'ll test them too.

A bunch of people make the same drop-in part, some under $1 each.

I\'d prefer to use the 5x20mm parts but they are not as common.
 
On Mon, 24 Jul 2023 18:38:15 -0700, boB <boB@K7IQ.com> wrote:

On Mon, 24 Jul 2023 18:15:44 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs

I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.

Dropout would be fast!

Yes, the high voltage transistor can do the work as long a it can take
the energy. I do that too when I need turn-off to be fast.
Otherwise, I just use a cache diode across the coil.

The circulating current with a regular diode will slow the switch off
but quite a lot. Sometimes it\'s ok but sometimes, like with line
connected inverter/charger, we need it to turn off in a couple of ms
rather than 10 ms or so.

boB
Click to expand...

In some cases we can measure the contact currents and open the relay
if the customer pumps in too many amps. In that case, we\'d prefer to
open the contacts as fast as possible.

If I do add a part, it may as well be a zener to ground.
 
tirsdag den 25. juli 2023 kl. 03.16.00 UTC+2 skrev John Larkin:
On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs
I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.
Click to expand...

literally what the SSM3K357R is made for as shown in the datasheet
 
On Mon, 24 Jul 2023 18:59:58 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

tirsdag den 25. juli 2023 kl. 03.16.00 UTC+2 skrev John Larkin:
On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs
I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.

literally what the SSM3K357R is made for as shown in the datasheet
Click to expand...

We can probably do a footprint that allows the SSM or some other part.
We\'re paranoid about availability and sole-source lately.

The SSM is a slightly unusual package but it looks like it will work
in a standard SOT23 footprint. I\'ll get some and try them.
 
tirsdag den 25. juli 2023 kl. 04.24.47 UTC+2 skrev John Larkin:
On Mon, 24 Jul 2023 18:59:58 -0700 (PDT), Lasse Langwadt Christensen
lang...@fonz.dk> wrote:

tirsdag den 25. juli 2023 kl. 03.16.00 UTC+2 skrev John Larkin:
On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
pcdhSpamM...@electrooptical.net> wrote:

John Larkin <jla...@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs
I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.

literally what the SSM3K357R is made for as shown in the datasheet
We can probably do a footprint that allows the SSM or some other part.
We\'re paranoid about availability and sole-source lately.

The SSM is a slightly unusual package but it looks like it will work
in a standard SOT23 footprint. I\'ll get some and try them.
Click to expand...

afaict it uses the same footprint, the legs are just flat with the bottom instead of gullwing
 
On 25-July-23 8:41 am, John Larkin wrote:
https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.
Click to expand...

I\'d be concerned that whatever I thought the max flyback voltage could
be, there will be a combination of circumstances that conspire to
produce something higher on the day when that\'s most inconvenient.

E lets you choose the turn-off time as a trade against FET drain voltage.

Sylvia.
 
On a sunny day (Mon, 24 Jul 2023 15:41:16 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<m9vtbidjnfs514s4s26nhj59m1ojp8q2m1@4ax.com>:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?
Click to expand...

I would use A to be safe, pevents RF oscillations and delivers power back into the supply ;-)
 
On 25/07/2023 11:56 am, John Larkin wrote:
On Mon, 24 Jul 2023 18:38:15 -0700, boB <boB@K7IQ.com> wrote:

On Mon, 24 Jul 2023 18:15:44 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs

I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.

Dropout would be fast!

Yes, the high voltage transistor can do the work as long a it can take
the energy. I do that too when I need turn-off to be fast.
Otherwise, I just use a cache diode across the coil.

The circulating current with a regular diode will slow the switch off
but quite a lot. Sometimes it\'s ok but sometimes, like with line
connected inverter/charger, we need it to turn off in a couple of ms
rather than 10 ms or so.

boB

In some cases we can measure the contact currents and open the relay
if the customer pumps in too many amps. In that case, we\'d prefer to
open the contacts as fast as possible.

If I do add a part, it may as well be a zener to ground.
Click to expand...

What I usually do if there are multiple coils is share one zener between
all of the coil drivers, and have an individual diode from each drain to
the shared zener.

Having the zener to the supply rail rather than to ground is slightly
more energy-efficient, if the relays switch often, but requires some
amount of bulk capacitance to be present on the supply rail, which there
usually is anyway.
 
On 25/07/2023 9:49 pm, Chris Jones wrote:
On 25/07/2023 11:56 am, John Larkin wrote:
On Mon, 24 Jul 2023 18:38:15 -0700, boB <boB@K7IQ.com> wrote:

On Mon, 24 Jul 2023 18:15:44 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives
the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts
open at
full speed.

Cheers

Phil Hobbs

I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.

Dropout would be fast!

Yes, the high voltage transistor can do the work as long a it can take
the energy.  I do that too when I need turn-off to be fast.
Otherwise, I just use a cache diode across the coil.

The circulating current with a regular diode will slow the switch off
but quite a lot.  Sometimes it\'s ok but sometimes, like with line
connected inverter/charger, we need it to turn off in a couple of ms
rather than 10 ms or so.

boB

In some cases we can measure the contact currents and open the relay
if the customer pumps in too many amps. In that case, we\'d prefer to
open the contacts as fast as possible.

If I do add a part, it may as well be a zener to ground.


What I usually do if there are multiple coils is share one zener between
all of the coil drivers, and have an individual diode from each drain to
the shared zener.

Having the zener to the supply rail rather than to ground is slightly
more energy-efficient, if the relays switch often, but requires some
amount of bulk capacitance to be present on the supply rail, which there
usually is anyway.
Click to expand...

(on further thought the capacitance is only more necessary (than with
the zener to ground) if there is long wiring to the power supply, with
significant inductance)
 
On 24/07/2023 23:41, John Larkin wrote:
https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?
Click to expand...

I have used slew rate limited ...

<https://www.dropbox.com/scl/fi/oyf7ocfaolxbr0zf6zi68/slewrelaydrive.jpg?rlkey=3zpl2gkfu62k5ua46hk9j92vh&raw=1>

a less minimal version of your \"G\". I also like \"B\" it is very cheap
very reliable and can tailor release time and peak voltage just the way
you like.

piglet
 
On Tue, 25 Jul 2023 21:49:49 +1000, Chris Jones
<lugnut808@spam.yahoo.com> wrote:

On 25/07/2023 11:56 am, John Larkin wrote:
On Mon, 24 Jul 2023 18:38:15 -0700, boB <boB@K7IQ.com> wrote:

On Mon, 24 Jul 2023 18:15:44 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Mon, 24 Jul 2023 23:25:47 -0000 (UTC), Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?



TVS across the coil. That sometimes helps a bit with keeping the rail
clean, and (unlike the shunt rectifier approach) lets the contacts open at
full speed.

Cheers

Phil Hobbs

I\'d like to use a sot-23 fet and nothing else. I\'ll brickwall 120
7x20mm relays and have to put the drivers between the pins on the
bottom side of the board and I need room for hundreds of fat traces
too.

It\'s tough to get a flyback boost of 10:1, and I\'m hoping that a relay
coil can\'t do that. I could use a 100 or 150 volt fet and the spike
voltage might not get that high.

Dropout would be fast!

Yes, the high voltage transistor can do the work as long a it can take
the energy. I do that too when I need turn-off to be fast.
Otherwise, I just use a cache diode across the coil.

The circulating current with a regular diode will slow the switch off
but quite a lot. Sometimes it\'s ok but sometimes, like with line
connected inverter/charger, we need it to turn off in a couple of ms
rather than 10 ms or so.

boB

In some cases we can measure the contact currents and open the relay
if the customer pumps in too many amps. In that case, we\'d prefer to
open the contacts as fast as possible.

If I do add a part, it may as well be a zener to ground.


What I usually do if there are multiple coils is share one zener between
all of the coil drivers, and have an individual diode from each drain to
the shared zener.

Having the zener to the supply rail rather than to ground is slightly
more energy-efficient, if the relays switch often, but requires some
amount of bulk capacitance to be present on the supply rail, which there
usually is anyway.
Click to expand...

Yes, there could be a clamp supply that is some multiple of my +12
relay coil supply. But I\'d have to distribute it to all 120 relays,
which would probably add another layer to the PC board. A zener can
dump to ground.

I don\'t think we\'d switch often enough to fry a zener. Relays don\'t
specify coil inductance, so I\'ll have to measure a few to estimate
stored energy.

I guess some of the energy is stored mechanically, so static
inductance isn\'t the whole story.

This is what I have so far:

https://www.dropbox.com/scl/fi/pt0s654nj3549ox9wys11/P948_7mm_5.jpg?rlkey=m8su7owc3k3c9o3n59ouc1wje&raw=1

Little SOT23 mosfets under each relay and an FPGA driving them. Lots
of traces.
 
On Tue, 25 Jul 2023 13:15:20 +1000, Sylvia Else <sylvia@email.invalid>
wrote:

On 25-July-23 8:41 am, John Larkin wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

I\'d be concerned that whatever I thought the max flyback voltage could
be, there will be a combination of circumstances that conspire to
produce something higher on the day when that\'s most inconvenient.

E lets you choose the turn-off time as a trade against FET drain voltage.

Sylvia.
Click to expand...

Sure, but I need to route fat traces to 120 relays on a 6-layer board.
Parts get in the way.
 
On Tue, 25 Jul 2023 05:20:21 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Mon, 24 Jul 2023 15:41:16 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
m9vtbidjnfs514s4s26nhj59m1ojp8q2m1@4ax.com>:


https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?

I would use A to be safe, pevents RF oscillations and delivers power back into the supply ;-)
Click to expand...

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.
 
On Tue, 25 Jul 2023 15:04:59 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 24/07/2023 23:41, John Larkin wrote:

https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?


I have used slew rate limited ...

https://www.dropbox.com/scl/fi/oyf7ocfaolxbr0zf6zi68/slewrelaydrive.jpg?rlkey=3zpl2gkfu62k5ua46hk9j92vh&raw=1

a less minimal version of your \"G\". I also like \"B\" it is very cheap
very reliable and can tailor release time and peak voltage just the way
you like.

piglet
Click to expand...

B loses power when the relay is on, but the numbers aren\'t bad. The
relays use 200 mW and if the resistor is 4x the coil resistance, the
resistor loses 50 mW and the flyback is about 60 volts.
 
On Monday, July 24, 2023 at 6:41:33 PM UTC-4, John Larkin wrote:
https://www.dropbox.com/scl/fi/40slcbgbngggdcwwt95vi/Relay_Drivers.jpg?rlkey=gfai2trx0n6bnja2yl4hber7i&raw=1

I like C1, with just a high-enough-voltage mosfet that it survives the
max flyback voltage.

C2 would use some exotic avalanche-rated thing.

Everthing else needs more parts.

Any more?
Click to expand...

Is that a 200mW coil? So at 5V they have Rc = 25/0.2= 125R. But the abbreviated data sheet says it\'s Rc of 720R, which makes no sense whatsoever, unless \"coil power rating DC\" means just that for applications using overvoltage ( allows for 12V) speed-up. That kind of coil resistance makes me suspect the L/R is quite small, making the coil magnetic circuit quite speedy compared to armature movement. Do you have the actuate/ release times? And is this an 80/20 pull-in/ drop-out type, or something else? The actual delay from application of pull-in current to contact make can be measured, same for the drop-out current to contact break. I\'m guessing the drop-out break is longer because they all use contact over-travel on make to preserve contact material and reduce bounce. Anyway, getting a handle on those times and currents will determine the best reverse voltage method.

TE says some of that PCJ series are pending obsolescence.
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top