many relay drivers...

tirsdag den 25. juli 2023 kl. 18.17.29 UTC+2 skrev Fred Bloggs:
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?
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,
..
TE says some of that PCJ series are pending obsolescence.
Click to expand...

they come in difference version with different coil voltages, 5V coil is 125R, 12V coil is 720R
 
On Tuesday, July 25, 2023 at 12:46:56 PM UTC-4, Lasse Langwadt Christensen wrote:
tirsdag den 25. juli 2023 kl. 18.17.29 UTC+2 skrev Fred Bloggs:
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?
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,
..
TE says some of that PCJ series are pending obsolescence.
they come in difference version with different coil voltages, 5V coil is 125R, 12V coil is 720R
Click to expand...

The one 3V/5V I looked at said 200mW and 720R coil.
 
tirsdag den 25. juli 2023 kl. 18.49.22 UTC+2 skrev Fred Bloggs:
On Tuesday, July 25, 2023 at 12:46:56 PM UTC-4, Lasse Langwadt Christensen wrote:
tirsdag den 25. juli 2023 kl. 18.17.29 UTC+2 skrev Fred Bloggs:
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?
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,
..
TE says some of that PCJ series are pending obsolescence.
they come in difference version with different coil voltages, 5V coil is 125R, 12V coil is 720R
The one 3V/5V I looked at said 200mW and 720R coil.
Click to expand...

https://www.farnell.com/datasheets/1717899.pdf
 
On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<hcsvbi5qh32b4fm3go7mlkitktphr2qr8c@4ax.com>:

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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.
Click to expand...

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.
 
On Wed, 26 Jul 2023 05:03:17 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
hcsvbi5qh32b4fm3go7mlkitktphr2qr8c@4ax.com>:

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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.
Click to expand...

Adding 120+ diodes might cost another PCB layer.

I don\'t think a once-a-minute ringy thing would even show up on a
spectrum analyzer.
 
On a sunny day (Wed, 26 Jul 2023 06:42:07 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<vh82ci91224q6qmmj9bcs2uuu4dsb24ago@4ax.com>:

On Wed, 26 Jul 2023 05:03:17 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
hcsvbi5qh32b4fm3go7mlkitktphr2qr8c@4ax.com>:

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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.

Adding 120+ diodes might cost another PCB layer.
Click to expand...

You have 120 relays on one board???

I don\'t think a once-a-minute ringy thing would even show up on a
spectrum analyzer.
Click to expand...

No but it would screw up your radio\'s music perhaps.

Things happen, strange things..
\'Arte\' TV channel had \'The Blues brothers\' a movie last Sunday
I watched it.
Then I thought: \'should have recorded it (was in HD I have the lower resolution).
So looked and repeat was next day during day time, set a timer.
Thing started but aborted with \'USB error\' after about 2 GB...
sigh, buttons on remote no longer worked either...
So.. well, finally unplugged it and all worked again....
Many GB in HD... all in 4 GB sections, but now I am missing a part.
Looks like it was a mains dip.. 128 GB USB stick is behaving normal..
Now that movie, and driving on the wrong side of the road, ..
I guess many here have seen it..
reminded me of that night with Jerry, he was driving, road with barrier in the middle for the other way
he switched lanes and drove against the traffic .. now you have to know Jerry,
there is a stones song \'paint it black\' he was my neighbor and had his room painted black..
He asked me (while driving the wrong way) \'are you not afraid?
Well not really, but told him survival chances were better if we moved back to the right side of the road, which he eventually did,
pointed out the funeral place next to his parents house, did that make him do it?
Jerry was OK, met an old friend of him years later (he had moved), he told me Jerry had become very aggressive.
No idea if he is still around.
But a nice movie, good music... no silly effects, real stuff..
Those days...
 
On Wed, 26 Jul 2023 15:43:38 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Wed, 26 Jul 2023 06:42:07 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
vh82ci91224q6qmmj9bcs2uuu4dsb24ago@4ax.com>:

On Wed, 26 Jul 2023 05:03:17 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
hcsvbi5qh32b4fm3go7mlkitktphr2qr8c@4ax.com>:

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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.

Adding 120+ diodes might cost another PCB layer.

You have 120 relays on one board???
Click to expand...

Yes. Brickwalled. And we need to get a lot of very fat traces deep
into the array.

If I add the 48 polyfuses, so the customer doesn\'t fry my traces,
there\'s even less room.

https://www.dropbox.com/scl/fi/x8ily46c4igji6tlkjnrg/P948_polyfuses_5.jpg?rlkey=fot52eisaxq9g8l0hbmbt2gsc&raw=1

The mosfet relay drivers can go on the bottom, between the thru-hole
relay pins, but will block traces. Diodes would block more.

My customer designed a box to do this function, many years ago, back
when aerospace companies designed their own test gear. Nowadays, the
old engineers and techs retire and aren\'t replaced, and they can\'t
build or maintain their stuff any more. This is our version.
 
On Wed, 26 Jul 2023 12:28:30 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Wed, 26 Jul 2023 15:43:38 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Wed, 26 Jul 2023 06:42:07 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
vh82ci91224q6qmmj9bcs2uuu4dsb24ago@4ax.com>:

On Wed, 26 Jul 2023 05:03:17 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
hcsvbi5qh32b4fm3go7mlkitktphr2qr8c@4ax.com>:

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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.

Adding 120+ diodes might cost another PCB layer.

You have 120 relays on one board???

Yes. Brickwalled. And we need to get a lot of very fat traces deep
into the array.

If I add the 48 polyfuses, so the customer doesn\'t fry my traces,
there\'s even less room.

https://www.dropbox.com/scl/fi/x8ily46c4igji6tlkjnrg/P948_polyfuses_5.jpg?rlkey=fot52eisaxq9g8l0hbmbt2gsc&raw=1

The mosfet relay drivers can go on the bottom, between the thru-hole
relay pins, but will block traces. Diodes would block more.

My customer designed a box to do this function, many years ago, back
when aerospace companies designed their own test gear. Nowadays, the
old engineers and techs retire and aren\'t replaced, and they can\'t
build or maintain their stuff any more. This is our version.
Click to expand...

Looks great !

BUT I hope that those are Through-Hole and not SMT in case you need to
change one.

boB
 
torsdag den 27. juli 2023 kl. 05.10.38 UTC+2 skrev boB:
On Wed, 26 Jul 2023 12:28:30 -0700, John Larkin
jla...@highlandSNIPMEtechnology.com> wrote:

On Wed, 26 Jul 2023 15:43:38 GMT, Jan Panteltje <al...@comet.invalid
wrote:

On a sunny day (Wed, 26 Jul 2023 06:42:07 -0700) it happened John Larkin
jla...@highlandSNIPMEtechnology.com> wrote in
vh82ci91224q6qmmj...@4ax.com>:

On Wed, 26 Jul 2023 05:03:17 GMT, Jan Panteltje <al...@comet.invalid
wrote:

On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
jla...@highlandSNIPMEtechnology.com> wrote in
hcsvbi5qh32b4fm3g...@4ax.com>:

On Tue, 25 Jul 2023 05:20:21 GMT, Jan Panteltje <al...@comet.invalid
wrote:

On a sunny day (Mon, 24 Jul 2023 15:41:16 -0700) it happened John Larkin
jla...@highlandSNIPMEtechnology.com> wrote in
m9vtbidjnfs514s4s...@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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.

Adding 120+ diodes might cost another PCB layer.

You have 120 relays on one board???

Yes. Brickwalled. And we need to get a lot of very fat traces deep
into the array.

If I add the 48 polyfuses, so the customer doesn\'t fry my traces,
there\'s even less room.

https://www.dropbox.com/scl/fi/x8ily46c4igji6tlkjnrg/P948_polyfuses_5.jpg?rlkey=fot52eisaxq9g8l0hbmbt2gsc&raw=1

The mosfet relay drivers can go on the bottom, between the thru-hole
relay pins, but will block traces. Diodes would block more.

My customer designed a box to do this function, many years ago, back
when aerospace companies designed their own test gear. Nowadays, the
old engineers and techs retire and aren\'t replaced, and they can\'t
build or maintain their stuff any more. This is our version.
Looks great !

BUT I hope that those are Through-Hole and not SMT in case you need to
change one.
Click to expand...

SMD would take up quite a bit more space
 
On a sunny day (Wed, 26 Jul 2023 12:28:30 -0700) it happened John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote in
<68s2cihg5o9vsu5lmjj7e3nv0io1u9vf7d@4ax.com>:

On Wed, 26 Jul 2023 15:43:38 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Wed, 26 Jul 2023 06:42:07 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
vh82ci91224q6qmmj9bcs2uuu4dsb24ago@4ax.com>:

On Wed, 26 Jul 2023 05:03:17 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
hcsvbi5qh32b4fm3go7mlkitktphr2qr8c@4ax.com>:

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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.

Adding 120+ diodes might cost another PCB layer.

You have 120 relays on one board???

Yes. Brickwalled. And we need to get a lot of very fat traces deep
into the array.

If I add the 48 polyfuses, so the customer doesn\'t fry my traces,
there\'s even less room.

https://www.dropbox.com/scl/fi/x8ily46c4igji6tlkjnrg/P948_polyfuses_5.jpg?rlkey=fot52eisaxq9g8l0hbmbt2gsc&raw=1
Click to expand...

Impressive!


The mosfet relay drivers can go on the bottom, between the thru-hole
relay pins, but will block traces. Diodes would block more.

My customer designed a box to do this function, many years ago, back
when aerospace companies designed their own test gear. Nowadays, the
old engineers and techs retire and aren\'t replaced, and they can\'t
build or maintain their stuff any more. This is our version.
Click to expand...

What about relay wear out, is it possible to replace one?
 
On Wed, 26 Jul 2023 20:22:17 -0700 (PDT), Lasse Langwadt Christensen
<langwadt@fonz.dk> wrote:

torsdag den 27. juli 2023 kl. 05.10.38 UTC+2 skrev boB:
On Wed, 26 Jul 2023 12:28:30 -0700, John Larkin
jla...@highlandSNIPMEtechnology.com> wrote:

On Wed, 26 Jul 2023 15:43:38 GMT, Jan Panteltje <al...@comet.invalid
wrote:

On a sunny day (Wed, 26 Jul 2023 06:42:07 -0700) it happened John Larkin
jla...@highlandSNIPMEtechnology.com> wrote in
vh82ci91224q6qmmj...@4ax.com>:

On Wed, 26 Jul 2023 05:03:17 GMT, Jan Panteltje <al...@comet.invalid
wrote:

On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
jla...@highlandSNIPMEtechnology.com> wrote in
hcsvbi5qh32b4fm3g...@4ax.com>:

On Tue, 25 Jul 2023 05:20:21 GMT, Jan Panteltje <al...@comet.invalid
wrote:

On a sunny day (Mon, 24 Jul 2023 15:41:16 -0700) it happened John Larkin
jla...@highlandSNIPMEtechnology.com> wrote in
m9vtbidjnfs514s4s...@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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.

Adding 120+ diodes might cost another PCB layer.

You have 120 relays on one board???

Yes. Brickwalled. And we need to get a lot of very fat traces deep
into the array.

If I add the 48 polyfuses, so the customer doesn\'t fry my traces,
there\'s even less room.

https://www.dropbox.com/scl/fi/x8ily46c4igji6tlkjnrg/P948_polyfuses_5.jpg?rlkey=fot52eisaxq9g8l0hbmbt2gsc&raw=1

The mosfet relay drivers can go on the bottom, between the thru-hole
relay pins, but will block traces. Diodes would block more.

My customer designed a box to do this function, many years ago, back
when aerospace companies designed their own test gear. Nowadays, the
old engineers and techs retire and aren\'t replaced, and they can\'t
build or maintain their stuff any more. This is our version.
Looks great !

BUT I hope that those are Through-Hole and not SMT in case you need to
change one.

SMD would take up quite a bit more space
Click to expand...

Yes. There are many drop-in sources for the 7x20mm SPST relay. We\'ll
selective-solder the pins and we need to dance around the
surface-mount mosfet drivers on the bottom, between the relay pins.
Another reason to avoid catch diodes.

We\'ll probably have to hand-load the relays. We might see if our
pick-and-place can do it but I suspect not.
 
On Thu, 27 Jul 2023 05:16:20 GMT, Jan Panteltje <alien@comet.invalid>
wrote:

On a sunny day (Wed, 26 Jul 2023 12:28:30 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
68s2cihg5o9vsu5lmjj7e3nv0io1u9vf7d@4ax.com>:

On Wed, 26 Jul 2023 15:43:38 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Wed, 26 Jul 2023 06:42:07 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
vh82ci91224q6qmmj9bcs2uuu4dsb24ago@4ax.com>:

On Wed, 26 Jul 2023 05:03:17 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
hcsvbi5qh32b4fm3go7mlkitktphr2qr8c@4ax.com>:

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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.

Adding 120+ diodes might cost another PCB layer.

You have 120 relays on one board???

Yes. Brickwalled. And we need to get a lot of very fat traces deep
into the array.

If I add the 48 polyfuses, so the customer doesn\'t fry my traces,
there\'s even less room.

https://www.dropbox.com/scl/fi/x8ily46c4igji6tlkjnrg/P948_polyfuses_5.jpg?rlkey=fot52eisaxq9g8l0hbmbt2gsc&raw=1

Impressive!


The mosfet relay drivers can go on the bottom, between the thru-hole
relay pins, but will block traces. Diodes would block more.

My customer designed a box to do this function, many years ago, back
when aerospace companies designed their own test gear. Nowadays, the
old engineers and techs retire and aren\'t replaced, and they can\'t
build or maintain their stuff any more. This is our version.

What about relay wear out, is it possible to replace one?
Click to expand...

Only by soldering. The box will have BIST, self-test, to check
everything. The customer\'s original didn\'t, and that was a problem.
 
On Thu, 27 Jul 2023 07:02:40 -0700, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Thu, 27 Jul 2023 05:16:20 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Wed, 26 Jul 2023 12:28:30 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
68s2cihg5o9vsu5lmjj7e3nv0io1u9vf7d@4ax.com>:

On Wed, 26 Jul 2023 15:43:38 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Wed, 26 Jul 2023 06:42:07 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
vh82ci91224q6qmmj9bcs2uuu4dsb24ago@4ax.com>:

On Wed, 26 Jul 2023 05:03:17 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
hcsvbi5qh32b4fm3go7mlkitktphr2qr8c@4ax.com>:

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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.

Adding 120+ diodes might cost another PCB layer.

You have 120 relays on one board???

Yes. Brickwalled. And we need to get a lot of very fat traces deep
into the array.

If I add the 48 polyfuses, so the customer doesn\'t fry my traces,
there\'s even less room.

https://www.dropbox.com/scl/fi/x8ily46c4igji6tlkjnrg/P948_polyfuses_5.jpg?rlkey=fot52eisaxq9g8l0hbmbt2gsc&raw=1

Impressive!


The mosfet relay drivers can go on the bottom, between the thru-hole
relay pins, but will block traces. Diodes would block more.

My customer designed a box to do this function, many years ago, back
when aerospace companies designed their own test gear. Nowadays, the
old engineers and techs retire and aren\'t replaced, and they can\'t
build or maintain their stuff any more. This is our version.

What about relay wear out, is it possible to replace one?

Only by soldering. The box will have BIST, self-test, to check
everything. The customer\'s original didn\'t, and that was a problem.
Click to expand...

We stress to our PCB layer outers that they need to make sure there is
enough copper pad area around the holes so that rework can be done.

Sometimes this doesn\'t get through to them.

boB
 
On Thu, 27 Jul 2023 21:02:47 -0700, boB <boB@K7IQ.com> wrote:

On Thu, 27 Jul 2023 07:02:40 -0700, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Thu, 27 Jul 2023 05:16:20 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Wed, 26 Jul 2023 12:28:30 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
68s2cihg5o9vsu5lmjj7e3nv0io1u9vf7d@4ax.com>:

On Wed, 26 Jul 2023 15:43:38 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Wed, 26 Jul 2023 06:42:07 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
vh82ci91224q6qmmj9bcs2uuu4dsb24ago@4ax.com>:

On Wed, 26 Jul 2023 05:03:17 GMT, Jan Panteltje <alien@comet.invalid
wrote:

On a sunny day (Tue, 25 Jul 2023 09:01:31 -0700) it happened John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote in
hcsvbi5qh32b4fm3go7mlkitktphr2qr8c@4ax.com>:

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 ;-)

That\'s no fun. Everybody does that.

The stored energy is dissipated in the diode and the coil resistance.

You could use it to make some high voltage rail on the flyback if the relays work often enough... :)
As to no fun: No lack of RF noise is important (you may need to pass some standards perhaps).
Driving on the right side of the road may seem dull but it is safer.
The diode thing has worked OK in millions of equipment for as long as there have been relay drivers.

Adding 120+ diodes might cost another PCB layer.

You have 120 relays on one board???

Yes. Brickwalled. And we need to get a lot of very fat traces deep
into the array.

If I add the 48 polyfuses, so the customer doesn\'t fry my traces,
there\'s even less room.

https://www.dropbox.com/scl/fi/x8ily46c4igji6tlkjnrg/P948_polyfuses_5.jpg?rlkey=fot52eisaxq9g8l0hbmbt2gsc&raw=1

Impressive!


The mosfet relay drivers can go on the bottom, between the thru-hole
relay pins, but will block traces. Diodes would block more.

My customer designed a box to do this function, many years ago, back
when aerospace companies designed their own test gear. Nowadays, the
old engineers and techs retire and aren\'t replaced, and they can\'t
build or maintain their stuff any more. This is our version.

What about relay wear out, is it possible to replace one?

Only by soldering. The box will have BIST, self-test, to check
everything. The customer\'s original didn\'t, and that was a problem.

We stress to our PCB layer outers that they need to make sure there is
enough copper pad area around the holes so that rework can be done.

Sometimes this doesn\'t get through to them.

boB
Click to expand...

We don\'t have many rework problems. We do have a bunch of the right
equipment, like fancy IR and hot air things. We can heat an area on
the bottom of a board and lift a relay out with no stress. Solder
suckers and wicking can damage pads and thru-hole plating.

We do enforce a minimum annular ring on pads and vias. I\'ve seen
boards with zero annular ring... a trace just disappears into a hole.
Creepy.
 
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