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From: "Don" <g@crcomp.net>
Newsgroups: sci.electronics.design
Subject: Re: CoB LED filament analysis
Date: Sun, 26 Apr 2026 04:44:36 -0000 (UTC)
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john larkin wrote:
> Don wrote:
>>john larkin wrote:
>>> Don wrote:
>>>> Don wrote:
>>
>><snip>
>>
>>>>Game over. Lessons learned:
>>>>
>>>> 1. Pease hated solderless breadboards for a good reason: they introduce
>>>>    stray capacitance. After the solderless breadboard is removed the
>>>>    filament's current curve reverts to its true form with voltage and
>>>>    current in phase.
>>>
>>> 10 pF maybe. A million times less than would explain what you are
>>> seeing.
>>>
>>> But yes, the plastic solderless things are awful.
>>>
>>> https://www.dropbox.com/scl/fi/pk2t79ipe26c62lw9xi82/Z412_Proto.JPG?rlkey=jypa4wdmgqsvwu0l51rx1x445&raw=1
>>
>>Bravo! If I remember correctly, you use a dental drill? My own freehand
>>dremel on copper isn't nearly as straight. Perhaps my new milling table
>>[1] will help.
>
> I use a Drenel with a carbide dental burr.
>
>
>
>>    My media tends towards universal board. As an artiste associate,
>>appreciate my abstract art arrangement:
>>
>>    <https://crcomp.net/ledfilament/circuit.png>
>>
>>Note how voltage and current perfectly align after the solderless
>>protoboard is swapped out and replaced by my abstract art arrangement:
>>
>>    <https://crcomp.net/ledfilament/curveprobe3.png>
>>
>
> That still doesn't look right. What's the value of the series shunt
> resistor?

OK, there's a fundamental misunderstanding. The green component on the
left hand side of my abstract art arrangement, entitled PROBE EMBRACES
LAMP, is a fuse. Because you can never be too careful with 1:1 isolation
transformer secondary Line voltages.
    The big red clamp on the right side is a current probe. (One of my
goals is to learn how to use it.) Its P2 < P1 decal is oriented to point
from a higher isolated Line to a lower isolated Line.
    And now that you mention it, the probe's current curve is relatively
fuzzy. Because it's being pushed to its limit. If I remember correctly,
a 100 ohm series shunt resistor paints a sharper trace. I'll drop the
probe and swap-in a series shunt soon and share its sharper current
curve.

Danke,

--
73, Don, WD7Q                                             veritas    _|_
                                                          liberabit   |
https://www.qsl.net/wd7q                                  vos         |