testing the TI switchers...

[John Larkin]

I really like the TPS5 family of tiny little switchers, but their
Spice models are, to be kind, absurd garbage. The first switcher on
our board simulates input power of 12 volts * 9 tera-amps.

We\'re well along on pcb layout of a new delay generator, but I really
want more confidence that everything will work first pass. So in
parallel we\'re prototyping the switchers.

https://www.dropbox.com/sh/gxvkrjd0fr7peft/AACsNPaUkMTtTOAVcS1qeJAna?dl=0

I added SMB coax connectors to the outputs. It\'s hard to measure
switcher noise and ripple with a scope probe.

The PCB has no solder mask on vias, which makes probing and hacking
easier. One can\'t do that on a dense board or it will make a zillion
shorts.

I like those cute Amazon banana jack things. They are almost free. My
management (ie, The Brat) won\'t let me use Amazon stuff in production,
but I can sneak them onto prototypes that won\'t be sold.

 

[Joe Gwinn]

On Sat, 12 Nov 2022 14:50:59 -0800, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 12 Nov 2022 14:25:30 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Fri, 11 Nov 2022 23:23:47 -0800 (PST), whit3rd <whit3rd@gmail.com
wrote:

On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/
making a gas-tight contact. For power safety ground, of course,
you want a connection OTHER than a fastener that can be loosened from outside
the box (like, a rivet, or externally-unreachable screwdown).

I could get some to try, but I think they would look klunky on an
external end plate. People already are whining about the undercut
flatheads, which extend maybe 20 mils above the panel.

These little boxes are powered from warts and usually bolted down, so
we don\'t need a big ground lug.


So you\'re using a thin head that\'s flat top and bottom to cut into the
conical surface?

(\"Flat head screw\" means countersunk in my lexicon, as opposed to (for
example) the painted oval head things that come packaged with outlet
plates from Home Depot.)

Cheers

Phil Hobbs

Looks like a regular flathead, but undercut below.

https://www.newportfasteners.com/10-32-x-1-4-machine-screws-phillips-flat-undercut-head-steel-zinc-plating-quantity-100-pcs.html?gclid=EAIaIQobChMIyc6f29up-wIVsClMCh3eIAyoEAQYASABEgK1rvD_BwE

(We\'re using 6-32 and metric on various boxes.)

Undercut is normally used to keep the screw from bottoming on the box
and making the thin end plate get loose, but the sharp edge also cuts
into the anodized countersink and makes a good ground.

Ahh. I wondered what exactly was being used. It\'s called a \"flat
undercut\" head.

..<https://www.newportfasteners.com/fastener-guides/screws-head-styles.html>

A regular flathead screw in an anodized countersink can be iffy
electrically. Parallel rubbing surfaces.

I\'d put a drop of Noalox on the screw before installation, covering
both the threaded part and the underside of the screw head.

Noalox will also act as an anti-seize compound.

..<https://www.idealind.com/us/en/shop/30-026.html>

Available at Lowes, Home Depot, et al.


Joe Gwinn

 

[John Larkin]

On Sat, 12 Nov 2022 18:21:42 -0500, Joe Gwinn <joegwinn@comcast.net>
wrote:

On Sat, 12 Nov 2022 14:50:59 -0800, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 12 Nov 2022 14:25:30 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Fri, 11 Nov 2022 23:23:47 -0800 (PST), whit3rd <whit3rd@gmail.com
wrote:

On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/
making a gas-tight contact. For power safety ground, of course,
you want a connection OTHER than a fastener that can be loosened from outside
the box (like, a rivet, or externally-unreachable screwdown).

I could get some to try, but I think they would look klunky on an
external end plate. People already are whining about the undercut
flatheads, which extend maybe 20 mils above the panel.

These little boxes are powered from warts and usually bolted down, so
we don\'t need a big ground lug.


So you\'re using a thin head that\'s flat top and bottom to cut into the
conical surface?

(\"Flat head screw\" means countersunk in my lexicon, as opposed to (for
example) the painted oval head things that come packaged with outlet
plates from Home Depot.)

Cheers

Phil Hobbs

Looks like a regular flathead, but undercut below.

https://www.newportfasteners.com/10-32-x-1-4-machine-screws-phillips-flat-undercut-head-steel-zinc-plating-quantity-100-pcs.html?gclid=EAIaIQobChMIyc6f29up-wIVsClMCh3eIAyoEAQYASABEgK1rvD_BwE

(We\'re using 6-32 and metric on various boxes.)

Undercut is normally used to keep the screw from bottoming on the box
and making the thin end plate get loose, but the sharp edge also cuts
into the anodized countersink and makes a good ground.

Ahh. I wondered what exactly was being used. It\'s called a \"flat
undercut\" head.

.<https://www.newportfasteners.com/fastener-guides/screws-head-styles.html

My mistake for calling it \"undercut flathead\" instead of \"flathead
undercut.\"

A regular flathead screw in an anodized countersink can be iffy
electrically. Parallel rubbing surfaces.

I\'d put a drop of Noalox on the screw before installation, covering
both the threaded part and the underside of the screw head.

Noalox will also act as an anti-seize compound.

.<https://www.idealind.com/us/en/shop/30-026.html

Available at Lowes, Home Depot, et al.


Joe Gwinn

Some of this is clean-room gear. Zinc particles might not be welcome.

 

[Michael Schwingen]

On 2022-11-11, olaf <olaf@criseis.ruhr.de> wrote:

https://www.dropbox.com/sh/gxvkrjd0fr7peft/AACsNPaUkMTtTOAVcS1qeJAna?dl=0

I am impressed by the LM3880. I did not know that something
like this exist.

Hm - yes, nice, but at a price where I can get a small microcontroller which
will do other tasks at the same time.

cu
Michael

 

[John Larkin]

On Fri, 11 Nov 2022 13:17:11 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
I really like the TPS5 family of tiny little switchers, but their
Spice models are, to be kind, absurd garbage. The first switcher on
our board simulates input power of 12 volts * 9 tera-amps.

We\'re well along on pcb layout of a new delay generator, but I
really want more confidence that everything will work first pass. So
in parallel we\'re prototyping the switchers.

https://www.dropbox.com/sh/gxvkrjd0fr7peft/AACsNPaUkMTtTOAVcS1qeJAna?dl=0




I added SMB coax connectors to the outputs. It\'s hard to measure
switcher noise and ripple with a scope probe.

Yup. We sprinkle U.FL footprints on our boards for the same reason.
They\'re cheap and small, and make probing a breeze.


The PCB has no solder mask on vias, which makes probing and hacking
easier. One can\'t do that on a dense board or it will make a zillion
shorts.

I like those cute Amazon banana jack things. They are almost free.
My management (ie, The Brat) won\'t let me use Amazon stuff in
production, but I can sneak them onto prototypes that won\'t be sold.

We use Aliexpress connectors and stuff in POCs and suchlike. Since
Hammond and Bud jacked up the prices on their extruded cases, we\'re
going to Aliexpress extrusions plus laser-cut end plates from SendCutSend.

Cheers

Phil Hobbs

We did our own extrusions to replace the dreadful Hammond stuff.

http://www.highlandtechnology.com/DSS/J736DS.shtml

http://www.highlandtechnology.com/DSS/T130DS.shtml

We laser them to do the artwork. We thought we were removing the
anodize, but I think we\'re just removing the dye. It\'s still
non-conductive.

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

 

[Joe Gwinn]

On Fri, 11 Nov 2022 13:10:40 -0800, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Fri, 11 Nov 2022 13:17:11 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
I really like the TPS5 family of tiny little switchers, but their
Spice models are, to be kind, absurd garbage. The first switcher on
our board simulates input power of 12 volts * 9 tera-amps.

We\'re well along on pcb layout of a new delay generator, but I
really want more confidence that everything will work first pass. So
in parallel we\'re prototyping the switchers.

https://www.dropbox.com/sh/gxvkrjd0fr7peft/AACsNPaUkMTtTOAVcS1qeJAna?dl=0




I added SMB coax connectors to the outputs. It\'s hard to measure
switcher noise and ripple with a scope probe.

Yup. We sprinkle U.FL footprints on our boards for the same reason.
They\'re cheap and small, and make probing a breeze.


The PCB has no solder mask on vias, which makes probing and hacking
easier. One can\'t do that on a dense board or it will make a zillion
shorts.

I like those cute Amazon banana jack things. They are almost free.
My management (ie, The Brat) won\'t let me use Amazon stuff in
production, but I can sneak them onto prototypes that won\'t be sold.

We use Aliexpress connectors and stuff in POCs and suchlike. Since
Hammond and Bud jacked up the prices on their extruded cases, we\'re
going to Aliexpress extrusions plus laser-cut end plates from SendCutSend.

Cheers

Phil Hobbs

We did our own extrusions to replace the dreadful Hammond stuff.

http://www.highlandtechnology.com/DSS/J736DS.shtml

http://www.highlandtechnology.com/DSS/T130DS.shtml

We laser them to do the artwork. We thought we were removing the
anodize, but I think we\'re just removing the dye. It\'s still
non-conductive.

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

You might consider using Noalox on the joint:

..<https://www.idealind.com/us/en/shop/30-026.html>


Joe Gwinn

 

[John Larkin]

On 13 Nov 2022 10:43:23 GMT, Michael Schwingen
<news-1513678000@discworld.dascon.de> wrote:

On 2022-11-11, olaf <olaf@criseis.ruhr.de> wrote:

https://www.dropbox.com/sh/gxvkrjd0fr7peft/AACsNPaUkMTtTOAVcS1qeJAna?dl=0

I am impressed by the LM3880. I did not know that something
like this exist.

Hm - yes, nice, but at a price where I can get a small microcontroller which
will do other tasks at the same time.

cu
Michael

A microcontroller has to be programmed, which has its own costs. And
it still needs guaranteed clean powerup and powerdown and a regulator
down from the 12/24 volt prime supply.

We have a 400-ball Zynq do do any computing that we need.

A reel of LM3880\'s cost us 44 cents each, not even rounding error on
product price.

 

[olaf]

John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:


>https://www.dropbox.com/sh/gxvkrjd0fr7peft/AACsNPaUkMTtTOAVcS1qeJAna?dl=0

I am impressed by the LM3880. I did not know that something
like this exist.

I added SMB coax connectors to the outputs. It\'s hard to measure
switcher noise and ripple with a scope probe.

Tek offers a TPR1000/4000 to help you out.

Olaf

 

[Joe Gwinn]

On Sat, 12 Nov 2022 18:19:53 -0800, John Larkin
<jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 12 Nov 2022 18:21:42 -0500, Joe Gwinn <joegwinn@comcast.net
wrote:

On Sat, 12 Nov 2022 14:50:59 -0800, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 12 Nov 2022 14:25:30 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Fri, 11 Nov 2022 23:23:47 -0800 (PST), whit3rd <whit3rd@gmail.com
wrote:

On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/
making a gas-tight contact. For power safety ground, of course,
you want a connection OTHER than a fastener that can be loosened from outside
the box (like, a rivet, or externally-unreachable screwdown).

I could get some to try, but I think they would look klunky on an
external end plate. People already are whining about the undercut
flatheads, which extend maybe 20 mils above the panel.

These little boxes are powered from warts and usually bolted down, so
we don\'t need a big ground lug.


So you\'re using a thin head that\'s flat top and bottom to cut into the
conical surface?

(\"Flat head screw\" means countersunk in my lexicon, as opposed to (for
example) the painted oval head things that come packaged with outlet
plates from Home Depot.)

Cheers

Phil Hobbs

Looks like a regular flathead, but undercut below.

https://www.newportfasteners.com/10-32-x-1-4-machine-screws-phillips-flat-undercut-head-steel-zinc-plating-quantity-100-pcs.html?gclid=EAIaIQobChMIyc6f29up-wIVsClMCh3eIAyoEAQYASABEgK1rvD_BwE

(We\'re using 6-32 and metric on various boxes.)

Undercut is normally used to keep the screw from bottoming on the box
and making the thin end plate get loose, but the sharp edge also cuts
into the anodized countersink and makes a good ground.

Ahh. I wondered what exactly was being used. It\'s called a \"flat
undercut\" head.

.<https://www.newportfasteners.com/fastener-guides/screws-head-styles.html



My mistake for calling it \"undercut flathead\" instead of \"flathead
undercut.\"

Yes; I was citing the standard term, versus a description. In this
case, both terms would work for google, but that is often not the
case.

A regular flathead screw in an anodized countersink can be iffy
electrically. Parallel rubbing surfaces.

I\'d put a drop of Noalox on the screw before installation, covering
both the threaded part and the underside of the screw head.

Noalox will also act as an anti-seize compound.

.<https://www.idealind.com/us/en/shop/30-026.html

Available at Lowes, Home Depot, et al.


Joe Gwinn

Some of this is clean-room gear. Zinc particles might not be welcome.

For clean rooms, probably not. What fraction of the users would this
be?

If necessary, there is a trick. After seating the zinc particles in
the aluminum with a screw used only for that (or a conical tool
pressed from above), wash the alnox off with solvent and assemble
using a clean screw. The zinc particles should largely be trapped in
the aluminum. I don\'t know if this is good enough for those clean
rooms.

Joe Gwinn

 

[Phil Hobbs]

John Larkin wrote:

On Sat, 12 Nov 2022 18:21:42 -0500, Joe Gwinn <joegwinn@comcast.net
wrote:

On Sat, 12 Nov 2022 14:50:59 -0800, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 12 Nov 2022 14:25:30 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Fri, 11 Nov 2022 23:23:47 -0800 (PST), whit3rd <whit3rd@gmail.com
wrote:

On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/
making a gas-tight contact. For power safety ground, of course,
you want a connection OTHER than a fastener that can be loosened from outside
the box (like, a rivet, or externally-unreachable screwdown).

I could get some to try, but I think they would look klunky on an
external end plate. People already are whining about the undercut
flatheads, which extend maybe 20 mils above the panel.

These little boxes are powered from warts and usually bolted down, so
we don\'t need a big ground lug.


So you\'re using a thin head that\'s flat top and bottom to cut into the
conical surface?

(\"Flat head screw\" means countersunk in my lexicon, as opposed to (for
example) the painted oval head things that come packaged with outlet
plates from Home Depot.)

Cheers

Phil Hobbs

Looks like a regular flathead, but undercut below.

https://www.newportfasteners.com/10-32-x-1-4-machine-screws-phillips-flat-undercut-head-steel-zinc-plating-quantity-100-pcs.html?gclid=EAIaIQobChMIyc6f29up-wIVsClMCh3eIAyoEAQYASABEgK1rvD_BwE

(We\'re using 6-32 and metric on various boxes.)

Undercut is normally used to keep the screw from bottoming on the box
and making the thin end plate get loose, but the sharp edge also cuts
into the anodized countersink and makes a good ground.

Ahh. I wondered what exactly was being used. It\'s called a \"flat
undercut\" head.

.<https://www.newportfasteners.com/fastener-guides/screws-head-styles.html



My mistake for calling it \"undercut flathead\" instead of \"flathead
undercut.\"


A regular flathead screw in an anodized countersink can be iffy
electrically. Parallel rubbing surfaces.

I\'d put a drop of Noalox on the screw before installation, covering
both the threaded part and the underside of the screw head.

Noalox will also act as an anti-seize compound.

.<https://www.idealind.com/us/en/shop/30-026.html

Available at Lowes, Home Depot, et al.


Joe Gwinn

Some of this is clean-room gear. Zinc particles might not be welcome.

In the tool core rather than the fab side of the wall, right?

Cheers

Phil Hobbs


--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[whit3rd]

On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
<https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/>
making a gas-tight contact. For power safety ground, of course,
you want a connection OTHER than a fastener that can be loosened from outside
the box (like, a rivet, or externally-unreachable screwdown).

 

[John Larkin]

On Sun, 13 Nov 2022 13:32:08 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Sat, 12 Nov 2022 18:21:42 -0500, Joe Gwinn <joegwinn@comcast.net
wrote:

On Sat, 12 Nov 2022 14:50:59 -0800, John Larkin
jlarkin@highlandSNIPMEtechnology.com> wrote:

On Sat, 12 Nov 2022 14:25:30 -0500, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Fri, 11 Nov 2022 23:23:47 -0800 (PST), whit3rd <whit3rd@gmail.com
wrote:

On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/
making a gas-tight contact. For power safety ground, of course,
you want a connection OTHER than a fastener that can be loosened from outside
the box (like, a rivet, or externally-unreachable screwdown).

I could get some to try, but I think they would look klunky on an
external end plate. People already are whining about the undercut
flatheads, which extend maybe 20 mils above the panel.

These little boxes are powered from warts and usually bolted down, so
we don\'t need a big ground lug.


So you\'re using a thin head that\'s flat top and bottom to cut into the
conical surface?

(\"Flat head screw\" means countersunk in my lexicon, as opposed to (for
example) the painted oval head things that come packaged with outlet
plates from Home Depot.)

Cheers

Phil Hobbs

Looks like a regular flathead, but undercut below.

https://www.newportfasteners.com/10-32-x-1-4-machine-screws-phillips-flat-undercut-head-steel-zinc-plating-quantity-100-pcs.html?gclid=EAIaIQobChMIyc6f29up-wIVsClMCh3eIAyoEAQYASABEgK1rvD_BwE

(We\'re using 6-32 and metric on various boxes.)

Undercut is normally used to keep the screw from bottoming on the box
and making the thin end plate get loose, but the sharp edge also cuts
into the anodized countersink and makes a good ground.

Ahh. I wondered what exactly was being used. It\'s called a \"flat
undercut\" head.

.<https://www.newportfasteners.com/fastener-guides/screws-head-styles.html



My mistake for calling it \"undercut flathead\" instead of \"flathead
undercut.\"


A regular flathead screw in an anodized countersink can be iffy
electrically. Parallel rubbing surfaces.

I\'d put a drop of Noalox on the screw before installation, covering
both the threaded part and the underside of the screw head.

Noalox will also act as an anti-seize compound.

.<https://www.idealind.com/us/en/shop/30-026.html

Available at Lowes, Home Depot, et al.


Joe Gwinn

Some of this is clean-room gear. Zinc particles might not be welcome.


In the tool core rather than the fab side of the wall, right?

Cheers

Phil Hobbs

This particular box is used in the sub-fab, the light source a floor
below the wafer fab, and in the wafer area itself.

We have an elaborate ritual where we clean each box in a laminar flow
hood and triple-bag each one.

The old Hammond boxes used self-tapping screws and liked to strew
metal shavings, which usually stayed inside the boxes.

 

[Michael Schwingen]

On 2022-11-13, John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote:

A microcontroller has to be programmed, which has its own costs. And
it still needs guaranteed clean powerup and powerdown and a regulator
down from the 12/24 volt prime supply.

The LM3880 also needs a regulated 5V supply. Programming is done by the
distributor before assembly (yes, that costs some additional cents).

A reel of LM3880\'s cost us 44 cents each, not even rounding error on
product price.

I was quoted similar prices for STM32G030 back before they went unobtainium
.... we now use GD32. The microcontroller does system management including
temperature and fan control, and protects the main CPU even if it locks up
hard and overheats.

cu
Michael

 

[John Larkin]

On Fri, 11 Nov 2022 23:23:47 -0800 (PST), whit3rd <whit3rd@gmail.com>
wrote:

On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/
making a gas-tight contact. For power safety ground, of course,
you want a connection OTHER than a fastener that can be loosened from outside
the box (like, a rivet, or externally-unreachable screwdown).

I could get some to try, but I think they would look klunky on an
external end plate. People already are whining about the undercut
flatheads, which extend maybe 20 mils above the panel.

These little boxes are powered from warts and usually bolted down, so
we don\'t need a big ground lug.

 

[John Larkin]

On Fri, 11 Nov 2022 22:30:40 +0100, olaf <olaf@criseis.ruhr.de> wrote:

John Larkin <jlarkin@highlandsnipmetechnology.com> wrote:


https://www.dropbox.com/sh/gxvkrjd0fr7peft/AACsNPaUkMTtTOAVcS1qeJAna?dl=0

I am impressed by the LM3880. I did not know that something
like this exist.

Yes, it was a real find. In my circuit, it trips when the +1v switcher
hits +0.5, and then it sequences the rest every 30 ms. The Zynq FPGA
wants to be, possibly needs to be, supply sequenced. The SRST# output
un-resets everything and starts the boot process.

I\'d prefer a slower version, but the 30 ms one was available.

R103 discharges the +1 rail during brownouts, to make sure the
sequencer runs when power returns. U15 guarantees a minimum brownout
time to let stuff discharge. Ideally no brownout or fumbling with a
wall-wart can hang the system up.

I added SMB coax connectors to the outputs. It\'s hard to measure
switcher noise and ripple with a scope probe.

Tek offers a TPR1000/4000 to help you out.

Olaf

There\'s still the ground clip. A coax gives a really solid ground from
the board to the scope, or to a preamp to see the tiny stuff.

With probes, you run out of hands too. SMB connectors are handy on
important things like clocks, so you can poke other things with
probes.

https://www.dropbox.com/s/8oefk1v8avr6l7a/Probe_Slips.jpg?raw=1

 

[Phil Hobbs]

John Larkin wrote:

On Fri, 11 Nov 2022 23:23:47 -0800 (PST), whit3rd <whit3rd@gmail.com
wrote:

On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/
making a gas-tight contact. For power safety ground, of course,
you want a connection OTHER than a fastener that can be loosened from outside
the box (like, a rivet, or externally-unreachable screwdown).

I could get some to try, but I think they would look klunky on an
external end plate. People already are whining about the undercut
flatheads, which extend maybe 20 mils above the panel.

These little boxes are powered from warts and usually bolted down, so
we don\'t need a big ground lug.

So you\'re using a thin head that\'s flat top and bottom to cut into the
conical surface?

(\"Flat head screw\" means countersunk in my lexicon, as opposed to (for
example) the painted oval head things that come packaged with outlet
plates from Home Depot.)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[whit3rd]

On Saturday, November 12, 2022 at 7:42:57 AM UTC-8, John Larkin wrote:

On Fri, 11 Nov 2022 23:23:47 -0800 (PST), whit3rd <whi...@gmail.com
wrote:
On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/

I could get some to try, but I think they would look klunky on an
external end plate. People already are whining about the undercut
flatheads, which extend maybe 20 mils above the panel.

With a good adjustable stop, you could countersink the endplates for your choice of
extension; 2 mils above, flush, two mils below...
<https://www.mscdirect.com/product/details/32243370>

 

[Joe Gwinn]

On Sat, 12 Nov 2022 14:25:30 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Fri, 11 Nov 2022 23:23:47 -0800 (PST), whit3rd <whit3rd@gmail.com
wrote:

On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/
making a gas-tight contact. For power safety ground, of course,
you want a connection OTHER than a fastener that can be loosened from outside
the box (like, a rivet, or externally-unreachable screwdown).

I could get some to try, but I think they would look klunky on an
external end plate. People already are whining about the undercut
flatheads, which extend maybe 20 mils above the panel.

These little boxes are powered from warts and usually bolted down, so
we don\'t need a big ground lug.


So you\'re using a thin head that\'s flat top and bottom to cut into the
conical surface?

(\"Flat head screw\" means countersunk in my lexicon, as opposed to (for
example) the painted oval head things that come packaged with outlet
plates from Home Depot.)

Flat head is the correct term for the kind that goes flush in a
countersunk (conical) hole. The oval things have \"oval\" heads.

Here is the rest of the chart:

..<https://www.boltdepot.com/fastener-information/type-chart.aspx>

The bible for all such things is \"Machinery\'s Handbook\", first edition
published in 1914, and continuously ever since. Current is the 31st
edition.

..<https://books.industrialpress.com/9780831137311/machinerys-handbook-toolbox/>

There are lots of used copies available for small dollars in such as
used tool stores (and eBay).

Older editions are perfectly serviceable, especially for a small shop
with manual machines. I use the 27th edition, and also the 25th
edition.

The original size was meant to fit into the upper center drawer of a
standard machinist\'s 8-drawer toolbox, such as that made by Kennedy.
This size is now known as a \"toolbox\" edition, and it\'s larger version
is a \"big-print\" edition.

Joe Gwinn

 

[Phil Hobbs]

John Larkin wrote:

I really like the TPS5 family of tiny little switchers, but their
Spice models are, to be kind, absurd garbage. The first switcher on
our board simulates input power of 12 volts * 9 tera-amps.

We\'re well along on pcb layout of a new delay generator, but I
really want more confidence that everything will work first pass. So
in parallel we\'re prototyping the switchers.

https://www.dropbox.com/sh/gxvkrjd0fr7peft/AACsNPaUkMTtTOAVcS1qeJAna?dl=0




I added SMB coax connectors to the outputs. It\'s hard to measure
switcher noise and ripple with a scope probe.

Yup. We sprinkle U.FL footprints on our boards for the same reason.
They\'re cheap and small, and make probing a breeze.

The PCB has no solder mask on vias, which makes probing and hacking
easier. One can\'t do that on a dense board or it will make a zillion
shorts.

I like those cute Amazon banana jack things. They are almost free.
My management (ie, The Brat) won\'t let me use Amazon stuff in
production, but I can sneak them onto prototypes that won\'t be sold.

We use Aliexpress connectors and stuff in POCs and suchlike. Since
Hammond and Bud jacked up the prices on their extruded cases, we\'re
going to Aliexpress extrusions plus laser-cut end plates from SendCutSend.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Sat, 12 Nov 2022 14:25:30 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

John Larkin wrote:
On Fri, 11 Nov 2022 23:23:47 -0800 (PST), whit3rd <whit3rd@gmail.com
wrote:

On Friday, November 11, 2022 at 1:10:53 PM UTC-8, John Larkin wrote:

We do need to be careful that everything is solidly grounded. Undercut
flathead screws cut into anodized countersinks pretty well.

They make a reliable ground if you use these washers
https://www.mcmaster.com/washers/countersunk-external-tooth-lock-washers/
making a gas-tight contact. For power safety ground, of course,
you want a connection OTHER than a fastener that can be loosened from outside
the box (like, a rivet, or externally-unreachable screwdown).

I could get some to try, but I think they would look klunky on an
external end plate. People already are whining about the undercut
flatheads, which extend maybe 20 mils above the panel.

These little boxes are powered from warts and usually bolted down, so
we don\'t need a big ground lug.


So you\'re using a thin head that\'s flat top and bottom to cut into the
conical surface?

(\"Flat head screw\" means countersunk in my lexicon, as opposed to (for
example) the painted oval head things that come packaged with outlet
plates from Home Depot.)

Cheers

Phil Hobbs

Looks like a regular flathead, but undercut below.

https://www.newportfasteners.com/10-32-x-1-4-machine-screws-phillips-flat-undercut-head-steel-zinc-plating-quantity-100-pcs.html?gclid=EAIaIQobChMIyc6f29up-wIVsClMCh3eIAyoEAQYASABEgK1rvD_BwE

(We\'re using 6-32 and metric on various boxes.)

Undercut is normally used to keep the screw from bottoming on the box
and making the thin end plate get loose, but the sharp edge also cuts
into the anodized countersink and makes a good ground.

A regular flathead screw in an anodized countersink can be iffy
electrically. Parallel rubbing surfaces.