From: pcdhSpamMeSenseless@electrooptical.net
john larkin wrote:
> On Mon, 26 Jan 2026 13:12:21 -0500, Phil Hobbs
> wrote:
>
>> On 2026-01-26 11:48, john larkin wrote:
>>> On Tue, 27 Jan 2026 03:36:36 +1100, Bill Sloman
>>> wrote:
>>>
>>>> On 27/01/2026 2:53 am, john larkin wrote:
>>>>> On Sun, 25 Jan 2026 22:44:02 -0500, legg wrote:
>>>>>
>>>>>> On Sun, 25 Jan 2026 08:08:48 -0800, john larkin
>>>>>> wrote:
>>>>>>
>>>>>>> On Sun, 25 Jan 2026 08:51:24 -0500, legg wrote:
>>>>>>>
>>>>>>>> On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid
>>>>>>>> (Liz Tuddenham) wrote:
>>>>>>>>
>>>>>>
>>>>>>>> In applications where power levels are important, pot core orientation
>>>>>>>> will affect 'N' in the flux density concentration, and produce early
>>>>>>>> saturation at the location where minimum x-sectional area occurs.
>>>>>>>>
>>>>>>>> RL
>>>>>>>
>>>>>>> That should have a small effect on my pulser. Ill try it.
>>>>>>>
>>>>>>> I got a 2% change in inductance when I rotated the core halves.
>>>>>>>
>>>>>>>
>>>>>>> John Larkin
>>>>>>> Highland Tech Glen Canyon Design Center
>>>>>>> Lunatic Fringe Electronics
>>>>>>
>>>>>> 2% FREE x-sectional area, and an indication that the previous
>>>>>> misalignment doesn't dominate minimum value.
>>>>>>
>>>>>> Mind you, you can get a similar change just by forcing out
>>>>>> the fluff and detritus present at the contacting surfaces.
>>>>>> That might be what you're actually seeing, even if the core
>>>>>> is gapped.
>>>>>>
>>>>>> In pot cores, minimum x-section usually occurs where the centre
>>>>>> core meets the top and bottom plates. In parts shapes designed
>>>>>> for power applications, this is usually corrected.
>>>>>>
>>>>>> This core rotation can be used as a tolerance trim, where
>>>>>> needed, but anything like that before impregnation is probably
>>>>>> just biting fart bubbles.
>>>>>
>>>>> Impregnation?
>>>>
>>>> Some people like to lock the windings and the leads in place with a
>>>> heavy layer of encapsulant. This works better if you put the part to
>>>> encapsulated under vacuum before you pour on the encapsulant.
>>>>
>>>> I've never seen it done, but I've heard about it. It's apparently very
>>>> messy.
>>>
>>> Wet stuff is messy, really nasty in production. In the case of a
>>> txline transformer made with a few turns of coax, there's no reason to
>>> pot it.
>>>
>>> We just spin a few turns on a bobbin and clamp it into the pot core.
>>> If it got sloppy, a tie-wrap would secure things.
>>>
>>> Some people like the idea of potting things. Weird.
>>
>> Last year we did a TDR that had to survive being pounded into hardpan
>> with a slide hammer (>20k gees). Potting was the right answer there!
>>
>> We put in small bits of foam sticky tape to keep the epoxy from trashing
>> the pulse shapes. If we did it again, we'd probably go to a six-layer
>> board and use stripline to avoid the problem (mostly).
>
> Hard-cure epoxy can crush and destroy parts too. And, I've heard,
> wreck opamp offsets.
And make voltage references drift. Softer epoxy helps, or else a thin layer
of RTV applied to the components before potting.
> JLC does cheap 6-layers.
They’re our usual vendor for non-government stuff. Having LCSC attached
makes them more attractive than PCBWay.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC /
Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
|
