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From: Joe Gwinn <joegwinn@comcast.net>
Newsgroups: sci.electronics.design
Subject: Re: Instead scopes
Date: Mon, 02 Sep 2024 12:39:19 -0400
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On Mon, 02 Sep 2024 08:36:53 -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.
>
>That's another function of the gap-pad material. And the flattish part
>of the circular solenoid windings make a big contact area into the
>pads, for more heat transfer.

All good.  Needs to be in the drawing.


>>I'd specify the coil dimensions, not the mandrel dimensions, which may
>>be provided as a helpful suggestion only.
>
>It would be cool is the bottom of the windings were actually flat, a
>square or elliptical winding, for more heat transfer area. 

..<https://www.mcmaster.com/products/~/d-profile-rotary-shafts-5/?s=shafts%2Fshafts-2%7E%2Frotary-shafts-5%2Fdiameter%7E12-mm>

This is what's easily available.  If you make your own mandrels, they
can be any shape.  Make sure that at least one end has a index slot or
radial hole, to make winding easier by allowing the clock angle of the
mandrel easily fixed.

Joe Gwinn