Re: Instead scopes

On 3/09/2024 7:57 am, john larkin wrote:

On Mon, 2 Sep 2024 15:25:59 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
 

Joe Gwinn <joegwinn@comcast.net> wrote:

On Sun, 01 Sep 2024 19:49:39 -0700, john larkin
<jlarkin_highland_tech> wrote:
>

On Sun, 01 Sep 2024 17:43:32 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:
>

On Sun, 01 Sep 2024 13:17:03 -0700, john larkin
<jlarkin_highland_tech> wrote:
>

On Sun, 01 Sep 2024 15:53:46 -0400, Joe Gwinn <joegwinn@comcast.net>
wrote:
>

On Sun, 1 Sep 2024 17:55:58 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>

john larkin <jlarkin_highland_tech> wrote:

On Sun, 1 Sep 2024 17:45:46 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
>

On 30/08/2024 2:21 am, Jan Panteltje wrote:

On a sunny day (Fri, 30 Aug 2024 00:43:39 +1000) it happened Bill Sloman
<bill.sloman@ieee.org> wrote in <vaq1f2$jdj$1@dont-email.me>:
>

It's lot easier and quicker to bread-board a circuit in LTSpice than it
is to wire up a test circuit, but what that means is that you need to
make fewer real circuits and they are a lot more likely to work when tested.
>
That, on it's own, is enough to explain why labs look different today
than they did in the dark ages.

>
All it explains is boeings falling apart and astronuts ending up stuck at the ISS
and no moonlanding from the US, not even a probe.
Slimulations are _not_ realty and never will be.

>
But they can capture useful parts of reality, if you know what you are
doing.
>
John Larkin's simulated inductors tend not to have any parallel capacitance.

>
The trick is to know when it matters. ESR and core loss are usually
more important.
>
I designed this surface-mount inductor for my Pockels Cell driver,
after several tries using commercial parts. They all smoked.
>
It's wound on a specially marked Sharpie pen that we have carefully
reserved.

>
It better have a regular calibration schedule, or your semiconductor
customers may give you the raised eyebrow.

>
Hmm.  To be overly serious:  With traceability to NIST (US) or NPL
(UK) or the like.
>
The trend in standards is to eliminate standards tied to a physical
object.
>
I have a Sharpie in hand.  The barrel that is not covered by the cap
is a truncated cone, being 11.0 mm at the blunt end and 12.32 mm near
the cap, 73 mm away.

>
Mine is pretty cylindrical for the length of the coil. I expect that
the operator's (ie, my)  applied tension affects the radius too.

>
Most likely.
>
>

That inductor sees 25 amps p-p, roughly a sawtooth, at 4 MHz. The
Coilcraft parts that I tried all smoked, I guess from skin effect and
proximity effect.
>

>
Actually, all that's needed is to specify an ideal geometric shape,
with tolerances, in the formal documentation.
>
Joe Gwinn

>
I'll have someone start on a SolidWorks model.

>
I bet you need the standoff, so the lossy FR4 material isn't too
close.  That should be in the requirements as well.

>
The turns squish down into the gap-pad gunk, which is an OK heat
conductor. The PCB under the pad is a big copper pour, top and bottom,
with a zillion thermal vias.  There's more gap-pad on the underside of
the board to dump heat into the baseplate.
>
At 4 MHz, skin depth is 32 microns, so most of the copper is wasted.
That's why it gets so hot.
>
I tried three of the Coilcraft 1010VS parts in series, but they
smoked, probably skin+proximity effect.  Maybe parallel would have
been better.
>

>
I'd specify the coil dimensions, not the mandrel dimensions, which may
be provided as a helpful suggestion only.
>
Joe Gwinn

>
I could have a mandrel machined or 3D printed, to more accurately wind
the inductor. The improvement would be mostly cosmetic.

>
Or choose a 12mm OD mandrel, and adjust elsewhere.  The advantage of
12mm is that it's a common size. so just buy the rod and use it.
>
.<https://www.mcmaster.com/products/shafts/shafts-2~/rotary-shafts-5/diameter~12-mm/>
>
Actually, the requirement is a certain inductance while handling a
4-MHz sawtooth at 25 Amps (p-p), so the frequency band is roughly 4 to
20 MHz, to cover the first five harmonics  Which harmonic causes the
most heating?
>
The dimensions et al are the construction details needed for Highland
to be able to replicate the part without your help.
>

Lo these forty year gone, I had this RF gig that involved making a lot of
VHF LC oscillatior and filter protos.

 I still design LC oscillators!

You may put them together, but it sounds as if you evolve them rather than design them. And you'd have your own coil-winding gear if you did much of it. As Phil did.

We had a hand-cranked coil winder that had a good selection of cylindrical
steel mandrels with helical grooves to guide the wire, plus three or four
sheets with tables of measured values for single-layer coils of various
lengths.  With a couple of training runs, one learned how hard to pull on
the wire so that it would just spring free from the mandrel.
>
That made it easy to make nice looking, high-Q coils for the inductance
range of interest.  Good Medicine.

At George Kent in Luton (1973-76) I got to wind my own small-signal transformers. At Cambridge Instruments (1982-1991) I had to ask the coil-winders on the shop floor to do it for me.
--
Bill Sloman, Sydney