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From: john larkin <jlarkin_highland_tech>
Newsgroups: sci.electronics.design
Subject: Re: Instead scopes
Date: Sun, 01 Sep 2024 13:32:59 -0700
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On Mon, 2 Sep 2024 02:20:42 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:

>On 2/09/2024 12:09 am, john larkin 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.
>
>And you don't simulate them either.

Only when they matter.

 Simulation is - in part - about 
>letting the math throw up unexpected effects that appear when you hook 
>up a bunch of components. Knowing when it matter relies on the 
>simulation inside your head.
>
>> I designed this surface-mount inductor for my Pockels Cell driver,
>> after several tries using commercial parts. They all smoked.
>
>So you didn't read the data sheets carefully enough. 

Sure I did. They should have worked, based on the data sheets. 


It's not a part 
>that would usually be described as "surface mount". If you'd scraped the 
>enamel off the bottom of the coil and soldered each turn down onto an 
>isolated copper pad on the board, it probably would qualify as surface 
>mount, and would have had better thermal contact with the board.

I did that on the ends. I think the gap-pad works better thermally
than soldering every turn to the board.

Have you ever used a surface-mount coil that soldered every turn to
the board? Got a link?

>
>You might have had to make it as sintered metal 3-D printed structure to 
>get this to work - the wound coil looks a bit irregular.

Losses would be crazy.

>
>Lost wax casting could have worked too.
>
>> It's wound on a specially marked Sharpie pen that we have carefully
>> reserved.
>
>That defines it diameter. Measuring that with a vernier caliper would 
>give you a number you could document.
>
>> https://www.highlandtechnology.com/Product/T850
>
>> The grey gap-pad gives it some extra cooling. The board has lots of
>> thermal vias down to the water-cooled baseplate.
>
>If you'd wound it with copper tube you could have pumped water through 
>the tube, or made it a heat pipe.

And supply a water tank and a pump and water connectors?

>
>A 3-D printed structure would have offered more options.

Again, massive losses.

My inductor is cheap and simple and works.

If I get a gigantic order, I'll have a coil winding company make them
and retire the Sharpie.