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From: "Don" <g@crcomp.net>
Newsgroups: sci.electronics.design
Subject: Re: CoB LED filament analysis
Date: Sun, 26 Apr 2026 16:44:55 -0000 (UTC)
Organization: A noiseless patient Spider
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Xref: csiph.com sci.electronics.design:743416

See addendum 2 below.

See addendum below.

Arie de Muijnck wrote:
> Don wrote:
>> 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.
>
> Do you mean you were using the current probe without its required shunt (not 'series shunt') load resistor?
> That would explain most of the problems, including phase shift etc.

Yes, that's precisely what happened. At the very beginning, when this 
topic was still embedded in another thread, I openly asked if anyone
knew how to use the i1000s Fluke current probe. Yet you're the first
person to offer any insight into its operation.
    Fluke's own user guide is almost as useless as AI in this regard.
AI keeps circling around the same old set of websites using different
words to regurgitate its useless operating instructions with each
iteration.

Perhaps now that the key phrase "required load resistor" is known, my 
search results will return a useful operator guide. Thank you for your
insight.

Addendum:

And, by the way, there's yet another fundamental misunderstanding. In 
place of a full wave rectifier, the CoB LED utilizes two half-wave 
rectifiers, one at each end. Per piglet's xray interpretation, each 
half-wave rectifier consists of two diodes.

Addendum 2:

My attempts to appease audience obsession with a series shunt resistor
caused me to flip the scope's input impedance to "1M ohm AC" and
inadvertently leave it at that incorrect current probe setting.
After the scope's set to "1M ohm DC" a flat-line trace appears when
the two half-wave rectifiers are "off:"

    <https://crcomp.net/ledfilament/curveprobe4.png>

If that's what Arie means by "required shunt load resistor," then the
original current probe curve also shows a more-or-less flat-line trace:

    <https://crcomp.net/ledfilament/curveprobe.png>

And the anomaly again indicates capacitive current curve corruption
caused by the solderless breadboard.

In the end, AI did indeed mention the DC setting when using the probe.

Danke,

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