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?
many relay drivers
Started by ●July 24, 2023
Reply by ●July 24, 20232023-07-24
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 -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Reply by ●July 24, 20232023-07-24
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 HobbsI'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!
Reply by ●July 24, 20232023-07-24
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! > >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
Reply by ●July 24, 20232023-07-24
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
Reply by ●July 24, 20232023-07-24
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!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.
Reply by ●July 24, 20232023-07-24
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. > >boBIn 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.
Reply by ●July 24, 20232023-07-24
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
Reply by ●July 24, 20232023-07-24
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 datasheetWe 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.
Reply by ●July 25, 20232023-07-25
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.afaict it uses the same footprint, the legs are just flat with the bottom instead of gullwing
