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Groups > sci.electronics.design > #742925 > unrolled thread
| Started by | "Don" <g@crcomp.net> |
|---|---|
| First post | 2026-04-12 05:34 +0000 |
| Last post | 2026-04-25 15:47 +1000 |
| Articles | 20 on this page of 102 — 10 participants |
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CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-12 05:34 +0000
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-12 10:45 +0100
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-12 10:48 +0100
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-12 10:50 +0100
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-12 12:03 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-12 04:44 -0700
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-12 04:19 -0700
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-13 07:40 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-13 01:46 -0700
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-13 11:40 +0000
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-13 14:31 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-13 06:59 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-14 12:25 +0000
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-14 14:04 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 08:21 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-15 02:48 +1000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 11:14 -0700
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-14 19:25 +0100
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-14 19:43 +0100
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-14 20:19 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 12:54 -0700
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-14 19:42 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 12:57 -0700
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 13:02 -0700
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-14 21:29 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-14 19:10 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-15 11:36 +0000
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-15 12:35 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-21 14:39 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-21 08:41 -0700
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-21 08:54 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-21 16:55 +0000
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-22 03:54 +1000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-21 21:05 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-21 17:03 -0700
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-21 12:26 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-22 01:44 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-21 19:16 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-24 13:37 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 07:55 -0700
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 08:04 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-24 16:43 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-24 20:15 +0000
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-26 03:45 +1000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-25 11:14 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-25 22:56 +0000
Re: CoB LED filament analysis ehsjr <ehsjr@verizon.net> - 2026-04-25 21:33 -0400
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 02:18 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-25 20:08 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 04:44 +0000
Re: CoB LED filament analysis Arie de Muijnck <noreply@ademu.nl> - 2026-04-26 13:03 +0200
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 11:35 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 11:43 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 16:44 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-26 10:17 -0700
Re: CoB LED filament analysis Arie de Muijnck <noreply@ademu.nl> - 2026-04-26 19:58 +0200
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 19:22 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-05-19 03:30 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-05-19 08:26 -0700
Re: CoB LED filament analysis Arie de Muijnck <noreply@ademu.nl> - 2026-05-19 18:23 +0200
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-05-19 09:52 -0700
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-26 20:30 +0200
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-26 18:24 +0100
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-26 17:52 +0000
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-26 19:17 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-25 20:10 -0700
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-24 22:23 +0200
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 15:42 -0700
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-25 10:53 +0200
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-26 12:05 -0700
Re: CoB LED filament analysis piglet <erichpwagner@hotmail.com> - 2026-04-26 19:20 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-27 12:49 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-27 17:04 +1000
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-27 10:59 +0200
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-27 08:11 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-28 01:51 +1000
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-27 21:40 +0200
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-22 16:36 +0100
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-22 17:10 +0000
Re: CoB LED filament analysis JM <sunaecoNoChoppedPork@gmail.com> - 2026-04-22 18:17 +0100
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-22 17:31 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-22 18:14 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-22 11:23 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-22 18:43 +0000
Re: CoB LED filament analysis Jeroen Belleman <jeroen@nospam.please> - 2026-04-22 23:50 +0200
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-22 11:24 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-23 17:22 +1000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-23 07:58 -0700
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-23 17:15 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-23 21:26 +0000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-24 02:53 +0000
Re: CoB LED filament analysis John R Walliker <jrwalliker@gmail.com> - 2026-04-24 18:19 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 10:39 -0700
Re: CoB LED filament analysis John R Walliker <jrwalliker@gmail.com> - 2026-04-24 21:39 +0100
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 15:19 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-25 15:23 +1000
Re: CoB LED filament analysis "Don" <g@crcomp.net> - 2026-04-24 17:45 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 11:12 -0700
Re: CoB LED filament analysis Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> - 2026-04-24 18:30 +0000
Re: CoB LED filament analysis john larkin <jl@glen--canyon.com> - 2026-04-24 11:42 -0700
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-25 15:49 +1000
Re: CoB LED filament analysis Bill Sloman <bill.sloman@ieee.org> - 2026-04-25 15:47 +1000
Page 2 of 6 — ← Prev page 1 [2] 3 4 5 6 Next page →
| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Date | 2026-04-14 12:54 -0700 |
| Message-ID | <fo6ttkhglk0st63e5qvpdd56gtstomtnsh@4ax.com> |
| In reply to | #743024 |
On Tue, 14 Apr 2026 19:25:07 +0100, piglet <erichpwagner@hotmail.com> wrote: >On 14/04/2026 7:14 pm, john larkin wrote: >> On Wed, 15 Apr 2026 02:48:59 +1000, Bill Sloman <bill.sloman@ieee.org> >> wrote: >> >>> On 15/04/2026 1:21 am, john larkin wrote: >>>> On Tue, 14 Apr 2026 12:25:57 -0000 (UTC), "Don" <g@crcomp.net> wrote: >>>> >>>>> john larkin wrote: >>>>>> JM wrote: >>>>>> >>>>>>>> The diodes are visible next the resistors even the bond wires are faintly >>>>>>>> visible in the photo. >>>>>>> >>>>>>> You are probably correct, but easy enough for Don to check by using a >>>>>>> DC supply to check conduction with both polarities. >>>>>> >>>>>> Yes. Graph and don't guess. >>>>> >>>>> OK you guys, lots of excellent ideas! The DC idea's easiest, so it's >>>>> first. Big Clive's youtube link now appears as a Footnote on the >>>>> pertinent page: >>>>> >>>>> <https://crcomp.net/ledfilament/index.php> >>>>> >>>>> The webpage also includes a couple of new images where 68 VDC is applied >>>>> to barely illuminate the filament's CoBs, first in one direction, and >>>>> then the opposite. How do you graph such empirical data? >>>>> Anyhow, as expected, seven filament CoBs illuminate regardless of >>>>> DC polarity. Perhaps each of the seven CoBs contains a couple of LEDs, >>>>> cross connected to conduct current through the anode of one LED, while >>>>> the cathode of its coupled LED blocks current? >>>> >>>> The xray sure doesn't look like there is a bridge rectifier. >>> >>> The four rectifiers creating the bridge rectifier may not be mounted >>> together as a discrete bridge rectifier, but that doesn't stop them >>> working together to create the same effect. >>> >>>> https://crcomp.net/ledfilament/top.png >>>> >>>> so I expect the LEDs are connected antiparallel. >>> >>> That would mean twice as many LEDs, which would be a much more expensive >>> solution. >> >> There's no obvious bridge in the xray, but resolution isn't very good. >> >> There are ways to decap a plastic-potted IC. >> >>> >>>> If 68v is the turnon threshold, and a blue LED needs, say 2.8 to light >>>> up a bit, there are roughly 24 LEDs in series. >>> >>> There might be, if anybody could see them on the X-rays. Google says >>> that blue LED drop between 3.0V and 3.4V. Seven of the them would drop >>> between 21 and 24 V and enough resistance to soak up the remaining 44V >>> would make the current tolerably stable against self-heating in the LEDs >>> (whose forward voltage drops as the junction temperature increases). >>> >>> https://descargas.cetronic.es/WW05A3SBQ4-N.pdf >> >> Look at the V-I curve on that part. It conducts 1 mA at about 2.8 >> volts, and would be visible at way lower current. 1 uA might be >> visible in dim room light. >> >>> >>>> What someone should do is graph current vs voltage, both polarities. >>> >>> What John Larkin needs to do is to think a bit harder. >> >> Well, I do have a day job. >> >> >> John Larkin >> Highland Tech Glen Canyon Design Center >> Lunatic Fringe Electronics > > >Can you see the four diodes now ...? > ><https://www.dropbox.com/scl/fi/4kcz56xykw1780z3qad3w/COB_LED.pdf?rlkey=b5mz77rs8pbwzv7bt9n5sfae3&st=x8h1gsgq&raw=1> > >piglet Do you think those are diodes? What would the circuit be? They may just be wirebond pads. John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
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| From | JM <sunaecoNoChoppedPork@gmail.com> |
|---|---|
| Date | 2026-04-14 19:42 +0100 |
| Message-ID | <gd2ttk1isvsskqrg6qffiu2djc6m7c4p54@4ax.com> |
| In reply to | #743021 |
On Tue, 14 Apr 2026 08:21:18 -0700, john larkin <jl@glen--canyon.com> wrote: >On Tue, 14 Apr 2026 12:25:57 -0000 (UTC), "Don" <g@crcomp.net> wrote: > >>john larkin wrote: >>> JM wrote: >>> >>>>>The diodes are visible next the resistors even the bond wires are faintly >>>>>visible in the photo. >>>> >>>>You are probably correct, but easy enough for Don to check by using a >>>>DC supply to check conduction with both polarities. >>> >>> Yes. Graph and don't guess. >> >>OK you guys, lots of excellent ideas! The DC idea's easiest, so it's >>first. Big Clive's youtube link now appears as a Footnote on the >>pertinent page: >> >> <https://crcomp.net/ledfilament/index.php> >> >>The webpage also includes a couple of new images where 68 VDC is applied >>to barely illuminate the filament's CoBs, first in one direction, and >>then the opposite. How do you graph such empirical data? >> Anyhow, as expected, seven filament CoBs illuminate regardless of >>DC polarity. Perhaps each of the seven CoBs contains a couple of LEDs, >>cross connected to conduct current through the anode of one LED, while >>the cathode of its coupled LED blocks current? > >The xray sure doesn't look like there is a bridge rectifier. > >https://crcomp.net/ledfilament/top.png > >so I expect the LEDs are connected antiparallel. > >If 68v is the turnon threshold, and a blue LED needs, say 2.8 to light >up a bit, there are roughly 24 LEDs in series. > >What someone should do is graph current vs voltage, both polarities. > > >John Larkin >Highland Tech Glen Canyon Design Center >Lunatic Fringe Electronics https://mega.nz/file/h98BgYSS#xF8fYYcMfE7qY0TWBPLaC3QjEQ0eeRiZnUr_qJsqdx4 (Note that connections to a diode die are top/bottom). All he needs to do is measure the current at a couple of dc voltages (both enough to illuminate the LEDs) and calculate the series R from delta V/ delta I. What else is there to know? -- This email has been checked for viruses by Avast antivirus software. www.avast.com
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| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Date | 2026-04-14 12:57 -0700 |
| Message-ID | <cu6ttk9qad163kd929kq1fonljsq1gi5bl@4ax.com> |
| In reply to | #743025 |
On Tue, 14 Apr 2026 19:42:17 +0100, JM <sunaecoNoChoppedPork@gmail.com> wrote: >On Tue, 14 Apr 2026 08:21:18 -0700, john larkin <jl@glen--canyon.com> >wrote: > >>On Tue, 14 Apr 2026 12:25:57 -0000 (UTC), "Don" <g@crcomp.net> wrote: >> >>>john larkin wrote: >>>> JM wrote: >>>> >>>>>>The diodes are visible next the resistors even the bond wires are faintly >>>>>>visible in the photo. >>>>> >>>>>You are probably correct, but easy enough for Don to check by using a >>>>>DC supply to check conduction with both polarities. >>>> >>>> Yes. Graph and don't guess. >>> >>>OK you guys, lots of excellent ideas! The DC idea's easiest, so it's >>>first. Big Clive's youtube link now appears as a Footnote on the >>>pertinent page: >>> >>> <https://crcomp.net/ledfilament/index.php> >>> >>>The webpage also includes a couple of new images where 68 VDC is applied >>>to barely illuminate the filament's CoBs, first in one direction, and >>>then the opposite. How do you graph such empirical data? >>> Anyhow, as expected, seven filament CoBs illuminate regardless of >>>DC polarity. Perhaps each of the seven CoBs contains a couple of LEDs, >>>cross connected to conduct current through the anode of one LED, while >>>the cathode of its coupled LED blocks current? >> >>The xray sure doesn't look like there is a bridge rectifier. >> >>https://crcomp.net/ledfilament/top.png >> >>so I expect the LEDs are connected antiparallel. >> >>If 68v is the turnon threshold, and a blue LED needs, say 2.8 to light >>up a bit, there are roughly 24 LEDs in series. >> >>What someone should do is graph current vs voltage, both polarities. >> >> >>John Larkin >>Highland Tech Glen Canyon Design Center >>Lunatic Fringe Electronics > > >https://mega.nz/file/h98BgYSS#xF8fYYcMfE7qY0TWBPLaC3QjEQ0eeRiZnUr_qJsqdx4 > >(Note that connections to a diode die are top/bottom). What use would diodes be in series with the assumed end resistors? Draw a circuit please. > >All he needs to do is measure the current at a couple of dc voltages >(both enough to illuminate the LEDs) and calculate the series R from >delta V/ delta I. What else is there to know? John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
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| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Date | 2026-04-14 13:02 -0700 |
| Message-ID | <k67ttk5agdp2pimlga0nlqaet3r7mruir2@4ax.com> |
| In reply to | #743028 |
On Tue, 14 Apr 2026 12:57:15 -0700, john larkin <jl@glen--canyon.com> wrote: >On Tue, 14 Apr 2026 19:42:17 +0100, JM ><sunaecoNoChoppedPork@gmail.com> wrote: > >>On Tue, 14 Apr 2026 08:21:18 -0700, john larkin <jl@glen--canyon.com> >>wrote: >> >>>On Tue, 14 Apr 2026 12:25:57 -0000 (UTC), "Don" <g@crcomp.net> wrote: >>> >>>>john larkin wrote: >>>>> JM wrote: >>>>> >>>>>>>The diodes are visible next the resistors even the bond wires are faintly >>>>>>>visible in the photo. >>>>>> >>>>>>You are probably correct, but easy enough for Don to check by using a >>>>>>DC supply to check conduction with both polarities. >>>>> >>>>> Yes. Graph and don't guess. >>>> >>>>OK you guys, lots of excellent ideas! The DC idea's easiest, so it's >>>>first. Big Clive's youtube link now appears as a Footnote on the >>>>pertinent page: >>>> >>>> <https://crcomp.net/ledfilament/index.php> >>>> >>>>The webpage also includes a couple of new images where 68 VDC is applied >>>>to barely illuminate the filament's CoBs, first in one direction, and >>>>then the opposite. How do you graph such empirical data? >>>> Anyhow, as expected, seven filament CoBs illuminate regardless of >>>>DC polarity. Perhaps each of the seven CoBs contains a couple of LEDs, >>>>cross connected to conduct current through the anode of one LED, while >>>>the cathode of its coupled LED blocks current? >>> >>>The xray sure doesn't look like there is a bridge rectifier. >>> >>>https://crcomp.net/ledfilament/top.png >>> >>>so I expect the LEDs are connected antiparallel. >>> >>>If 68v is the turnon threshold, and a blue LED needs, say 2.8 to light >>>up a bit, there are roughly 24 LEDs in series. >>> >>>What someone should do is graph current vs voltage, both polarities. >>> >>> >>>John Larkin >>>Highland Tech Glen Canyon Design Center >>>Lunatic Fringe Electronics >> >> >>https://mega.nz/file/h98BgYSS#xF8fYYcMfE7qY0TWBPLaC3QjEQ0eeRiZnUr_qJsqdx4 >> >>(Note that connections to a diode die are top/bottom). > > >What use would diodes be in series with the assumed end resistors? > >Draw a circuit please. > > >> >>All he needs to do is measure the current at a couple of dc voltages >>(both enough to illuminate the LEDs) and calculate the series R from >>delta V/ delta I. What else is there to know? > >John Larkin >Highland Tech Glen Canyon Design Center >Lunatic Fringe Electronics If the ceramic slab has an upper positive rail and a lower neg rail, there could be a bridge with half the diodes on each end. John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
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| From | piglet <erichpwagner@hotmail.com> |
|---|---|
| Date | 2026-04-14 21:29 +0100 |
| Message-ID | <10rm82e$dqln$1@dont-email.me> |
| In reply to | #743028 |
On 14/04/2026 8:57 pm, john larkin wrote: > On Tue, 14 Apr 2026 19:42:17 +0100, JM > <sunaecoNoChoppedPork@gmail.com> wrote: > >> On Tue, 14 Apr 2026 08:21:18 -0700, john larkin <jl@glen--canyon.com> >> wrote: >> >>> On Tue, 14 Apr 2026 12:25:57 -0000 (UTC), "Don" <g@crcomp.net> wrote: >>> >>>> john larkin wrote: >>>>> JM wrote: >>>>> >>>>>>> The diodes are visible next the resistors even the bond wires are faintly >>>>>>> visible in the photo. >>>>>> >>>>>> You are probably correct, but easy enough for Don to check by using a >>>>>> DC supply to check conduction with both polarities. >>>>> >>>>> Yes. Graph and don't guess. >>>> >>>> OK you guys, lots of excellent ideas! The DC idea's easiest, so it's >>>> first. Big Clive's youtube link now appears as a Footnote on the >>>> pertinent page: >>>> >>>> <https://crcomp.net/ledfilament/index.php> >>>> >>>> The webpage also includes a couple of new images where 68 VDC is applied >>>> to barely illuminate the filament's CoBs, first in one direction, and >>>> then the opposite. How do you graph such empirical data? >>>> Anyhow, as expected, seven filament CoBs illuminate regardless of >>>> DC polarity. Perhaps each of the seven CoBs contains a couple of LEDs, >>>> cross connected to conduct current through the anode of one LED, while >>>> the cathode of its coupled LED blocks current? >>> >>> The xray sure doesn't look like there is a bridge rectifier. >>> >>> https://crcomp.net/ledfilament/top.png >>> >>> so I expect the LEDs are connected antiparallel. >>> >>> If 68v is the turnon threshold, and a blue LED needs, say 2.8 to light >>> up a bit, there are roughly 24 LEDs in series. >>> >>> What someone should do is graph current vs voltage, both polarities. >>> >>> >>> John Larkin >>> Highland Tech Glen Canyon Design Center >>> Lunatic Fringe Electronics >> >> >> https://mega.nz/file/h98BgYSS#xF8fYYcMfE7qY0TWBPLaC3QjEQ0eeRiZnUr_qJsqdx4 >> >> (Note that connections to a diode die are top/bottom). > > > What use would diodes be in series with the assumed end resistors? > > Draw a circuit please. > > >> >> All he needs to do is measure the current at a couple of dc voltages >> (both enough to illuminate the LEDs) and calculate the series R from >> delta V/ delta I. What else is there to know? > > John Larkin > Highland Tech Glen Canyon Design Center > Lunatic Fringe Electronics You ask, you get ... <https://www.dropbox.com/scl/fi/racdrahimk5nexxdjrm4u/COB_LED_SCH.pdf?rlkey=pdgijpu70o636nk2dz83x78jy&st=1s9g3bd2&raw=1> piglet
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| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Date | 2026-04-14 19:10 -0700 |
| Message-ID | <mrsttkt27b0r5d3njask1d829qeen6e1jc@4ax.com> |
| In reply to | #743031 |
On Tue, 14 Apr 2026 21:29:01 +0100, piglet <erichpwagner@hotmail.com> wrote: >On 14/04/2026 8:57 pm, john larkin wrote: >> On Tue, 14 Apr 2026 19:42:17 +0100, JM >> <sunaecoNoChoppedPork@gmail.com> wrote: >> >>> On Tue, 14 Apr 2026 08:21:18 -0700, john larkin <jl@glen--canyon.com> >>> wrote: >>> >>>> On Tue, 14 Apr 2026 12:25:57 -0000 (UTC), "Don" <g@crcomp.net> wrote: >>>> >>>>> john larkin wrote: >>>>>> JM wrote: >>>>>> >>>>>>>> The diodes are visible next the resistors even the bond wires are faintly >>>>>>>> visible in the photo. >>>>>>> >>>>>>> You are probably correct, but easy enough for Don to check by using a >>>>>>> DC supply to check conduction with both polarities. >>>>>> >>>>>> Yes. Graph and don't guess. >>>>> >>>>> OK you guys, lots of excellent ideas! The DC idea's easiest, so it's >>>>> first. Big Clive's youtube link now appears as a Footnote on the >>>>> pertinent page: >>>>> >>>>> <https://crcomp.net/ledfilament/index.php> >>>>> >>>>> The webpage also includes a couple of new images where 68 VDC is applied >>>>> to barely illuminate the filament's CoBs, first in one direction, and >>>>> then the opposite. How do you graph such empirical data? >>>>> Anyhow, as expected, seven filament CoBs illuminate regardless of >>>>> DC polarity. Perhaps each of the seven CoBs contains a couple of LEDs, >>>>> cross connected to conduct current through the anode of one LED, while >>>>> the cathode of its coupled LED blocks current? >>>> >>>> The xray sure doesn't look like there is a bridge rectifier. >>>> >>>> https://crcomp.net/ledfilament/top.png >>>> >>>> so I expect the LEDs are connected antiparallel. >>>> >>>> If 68v is the turnon threshold, and a blue LED needs, say 2.8 to light >>>> up a bit, there are roughly 24 LEDs in series. >>>> >>>> What someone should do is graph current vs voltage, both polarities. >>>> >>>> >>>> John Larkin >>>> Highland Tech Glen Canyon Design Center >>>> Lunatic Fringe Electronics >>> >>> >>> https://mega.nz/file/h98BgYSS#xF8fYYcMfE7qY0TWBPLaC3QjEQ0eeRiZnUr_qJsqdx4 >>> >>> (Note that connections to a diode die are top/bottom). >> >> >> What use would diodes be in series with the assumed end resistors? >> >> Draw a circuit please. >> >> >>> >>> All he needs to do is measure the current at a couple of dc voltages >>> (both enough to illuminate the LEDs) and calculate the series R from >>> delta V/ delta I. What else is there to know? >> >> John Larkin >> Highland Tech Glen Canyon Design Center >> Lunatic Fringe Electronics > >You ask, you get ... > ><https://www.dropbox.com/scl/fi/racdrahimk5nexxdjrm4u/COB_LED_SCH.pdf?rlkey=pdgijpu70o636nk2dz83x78jy&st=1s9g3bd2&raw=1> > >piglet Yes, that's probably it. John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
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| From | "Don" <g@crcomp.net> |
|---|---|
| Date | 2026-04-15 11:36 +0000 |
| Message-ID | <20260415a@crcomp.net> |
| In reply to | #743031 |
piglet <erichpwagner@hotmail.com> wrote:
> On 14/04/2026 8:57 pm, john larkin wrote:
>> On Tue, 14 Apr 2026 19:42:17 +0100, JM <sunaecoNoChoppedPork@gmail.com> wrote:
>>> On Tue, 14 Apr 2026 08:21:18 -0700, john larkin <jl@glen--canyon.com> wrote:
>>>> On Tue, 14 Apr 2026 12:25:57 -0000 (UTC), "Don" <g@crcomp.net> wrote:
>>>>> john larkin wrote:
>>>>>> JM wrote:
>>>>>>
>>>>>>>> The diodes are visible next the resistors even the bond wires are faintly
>>>>>>>> visible in the photo.
>>>>>>>
>>>>>>> You are probably correct, but easy enough for Don to check by using a
>>>>>>> DC supply to check conduction with both polarities.
>>>>>>
>>>>>> Yes. Graph and don't guess.
>>>>>
>>>>> OK you guys, lots of excellent ideas! The DC idea's easiest, so it's
>>>>> first. Big Clive's youtube link now appears as a Footnote on the
>>>>> pertinent page:
>>>>>
>>>>> <https://crcomp.net/ledfilament/index.php>
>>>>>
>>>>> The webpage also includes a couple of new images where 68 VDC is applied
>>>>> to barely illuminate the filament's CoBs, first in one direction, and
>>>>> then the opposite. How do you graph such empirical data?
>>>>> Anyhow, as expected, seven filament CoBs illuminate regardless of
>>>>> DC polarity. Perhaps each of the seven CoBs contains a couple of LEDs,
>>>>> cross connected to conduct current through the anode of one LED, while
>>>>> the cathode of its coupled LED blocks current?
>>>>
>>>> The xray sure doesn't look like there is a bridge rectifier.
>>>>
>>>> https://crcomp.net/ledfilament/top.png
>>>>
>>>> If 68v is the turnon threshold, and a blue LED needs, say 2.8 to light
>>>> up a bit, there are roughly 24 LEDs in series.
>>>>
>>>> What someone should do is graph current vs voltage, both polarities.
>>>
>>> https://mega.nz/file/h98BgYSS#xF8fYYcMfE7qY0TWBPLaC3QjEQ0eeRiZnUr_qJsqdx4
>>>
>>> (Note that connections to a diode die are top/bottom).
>>
>> What use would diodes be in series with the assumed end resistors?
>>
>> Draw a circuit please.
>>
>>> All he needs to do is measure the current at a couple of dc voltages
>>> (both enough to illuminate the LEDs) and calculate the series R from
>>> delta V/ delta I. What else is there to know?
>
> You ask, you get ...
>
> <https://www.dropbox.com/scl/fi/racdrahimk5nexxdjrm4u/COB_LED_SCH.pdf?rlkey=pdgijpu70o636nk2dz83x78jy&st=1s9g3bd2&raw=1>
Congratulations, you did it again!
Your adroit analysis is anticlimactic. Because it eliminates my
expectations of exotic electronic elements such as miniaturized
MOSFETs.
Yet, in retrospect, it's simple to see how power elements demand a
relatively large footprint in order to handle a high voltage. It's only
simple now because you saw it first.
Anyhow, your radiographic interpretation eloquently puts everything
into perspective. Is it possible for you to give me permission to include
it on the webpage with a credit to you?
You also confirm my suspicion of a half-wave rectifier at each end.
One half-wave connected to Line and another attached to Neutral. This
gives me enough insight to include an illustrative kicad schematic on
the page.
Then the only things left to do are a detailed write-up and a pesky
V-I curve. Even if the curve only shows a resistive load it still gives
me an excuse to teach myself how to handle a Fluke current probe.
--
73, Don, WD7Q veritas _|_
liberabit |
https://www.qsl.net/wd7q vos |
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| From | piglet <erichpwagner@hotmail.com> |
|---|---|
| Date | 2026-04-15 12:35 +0000 |
| Message-ID | <10ro0n7$tdn1$1@dont-email.me> |
| In reply to | #743037 |
Don <g@crcomp.net> wrote: > piglet <erichpwagner@hotmail.com> wrote: >> On 14/04/2026 8:57 pm, john larkin wrote: >>> On Tue, 14 Apr 2026 19:42:17 +0100, JM <sunaecoNoChoppedPork@gmail.com> wrote: >>>> On Tue, 14 Apr 2026 08:21:18 -0700, john larkin <jl@glen--canyon.com> wrote: >>>>> On Tue, 14 Apr 2026 12:25:57 -0000 (UTC), "Don" <g@crcomp.net> wrote: >>>>>> john larkin wrote: >>>>>>> JM wrote: >>>>>>> >>>>>>>>> The diodes are visible next the resistors even the bond wires are faintly >>>>>>>>> visible in the photo. >>>>>>>> >>>>>>>> You are probably correct, but easy enough for Don to check by using a >>>>>>>> DC supply to check conduction with both polarities. >>>>>>> >>>>>>> Yes. Graph and don't guess. >>>>>> >>>>>> OK you guys, lots of excellent ideas! The DC idea's easiest, so it's >>>>>> first. Big Clive's youtube link now appears as a Footnote on the >>>>>> pertinent page: >>>>>> >>>>>> <https://crcomp.net/ledfilament/index.php> >>>>>> >>>>>> The webpage also includes a couple of new images where 68 VDC is applied >>>>>> to barely illuminate the filament's CoBs, first in one direction, and >>>>>> then the opposite. How do you graph such empirical data? >>>>>> Anyhow, as expected, seven filament CoBs illuminate regardless of >>>>>> DC polarity. Perhaps each of the seven CoBs contains a couple of LEDs, >>>>>> cross connected to conduct current through the anode of one LED, while >>>>>> the cathode of its coupled LED blocks current? >>>>> >>>>> The xray sure doesn't look like there is a bridge rectifier. >>>>> >>>>> https://crcomp.net/ledfilament/top.png >>>>> >>>>> If 68v is the turnon threshold, and a blue LED needs, say 2.8 to light >>>>> up a bit, there are roughly 24 LEDs in series. >>>>> >>>>> What someone should do is graph current vs voltage, both polarities. >>>> >>>> https://mega.nz/file/h98BgYSS#xF8fYYcMfE7qY0TWBPLaC3QjEQ0eeRiZnUr_qJsqdx4 >>>> >>>> (Note that connections to a diode die are top/bottom). >>> >>> What use would diodes be in series with the assumed end resistors? >>> >>> Draw a circuit please. >>> >>>> All he needs to do is measure the current at a couple of dc voltages >>>> (both enough to illuminate the LEDs) and calculate the series R from >>>> delta V/ delta I. What else is there to know? >> >> You ask, you get ... >> >> <https://www.dropbox.com/scl/fi/racdrahimk5nexxdjrm4u/COB_LED_SCH.pdf?rlkey=pdgijpu70o636nk2dz83x78jy&st=1s9g3bd2&raw=1> > > Congratulations, you did it again! > Your adroit analysis is anticlimactic. Because it eliminates my > expectations of exotic electronic elements such as miniaturized > MOSFETs. > Yet, in retrospect, it's simple to see how power elements demand a > relatively large footprint in order to handle a high voltage. It's only > simple now because you saw it first. > Anyhow, your radiographic interpretation eloquently puts everything > into perspective. Is it possible for you to give me permission to include > it on the webpage with a credit to you? > You also confirm my suspicion of a half-wave rectifier at each end. > One half-wave connected to Line and another attached to Neutral. This > gives me enough insight to include an illustrative kicad schematic on > the page. > Then the only things left to do are a detailed write-up and a pesky > V-I curve. Even if the curve only shows a resistive load it still gives > me an excuse to teach myself how to handle a Fluke current probe. > > -- > 73, Don, WD7Q veritas _|_ > liberabit | > https://www.qsl.net/wd7q vos | > > Thank you. Please feel free to use my sketchy schematic as you wanted. The LEDs inside a bridge rectifier is hardly original. Because the resistors drop most of the voltage even cheap 1N914 type diodes would suffice in the bridge as the peak reverse voltage they see is just the Vf of the seven LEDs. -- piglet
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| From | "Don" <g@crcomp.net> |
|---|---|
| Date | 2026-04-21 14:39 +0000 |
| Message-ID | <20260421a@crcomp.net> |
| In reply to | #742925 |
Don wrote:
> Recent thread topic transitioned to a tentative opinion on a work-in-
> progress webpage:
>
> <https://crcomp.net/ledfilament/index.php>
>
> Radiography imparts interesting insight. Second opinions welcome!
> The current waveform flopped. Any advice on how to use a Fluke
> 80i-1000s connected to a Tek 2465B to display the 120 VAC current
> wave is appreciated in advance. Also, what does "P2 < P1" signify on
> the current probe?
Alright you guys, a couple of current curve images are now available on
the webpage. For the present case, in regards to the probe's "P2 < P1"
orientation decal, P1 designates Line while P2 indicates Neutral.
The probe provides a sharper, cleaner curve compared to the
resistor. Both curves illustrate how the silicon filament primarily
presents itself as a capacitive load.
The filament's high voltage combined with its low amperage degrades
resistor curve quality. It took a 10 M ohm resistive current sensor for
the half-wave rectification effect to become visible.
The probe curve's mostly blue trace shows the peak-to-peak Line
voltage. It's used to properly trigger the scope. (Perhaps the scope's
line trigger accomplishes the same result with less effort?) The probe
curve's mostly green trace shows the current, with peaks and valleys
created by half-wave rectification at each end of the filament.
The current curve is set to 2mV per division. Does anyone know how
to transpose it to mA?
Danke,
--
73, Don, WD7Q veritas _|_
liberabit |
https://www.qsl.net/wd7q vos |
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| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Date | 2026-04-21 08:41 -0700 |
| Message-ID | <3c6fuk16nn9tfhj24q3ulue347ab93jvh8@4ax.com> |
| In reply to | #743194 |
On Tue, 21 Apr 2026 14:39:14 -0000 (UTC), "Don" <g@crcomp.net> wrote: >Don wrote: >> Recent thread topic transitioned to a tentative opinion on a work-in- >> progress webpage: >> >> <https://crcomp.net/ledfilament/index.php> >> >> Radiography imparts interesting insight. Second opinions welcome! >> The current waveform flopped. Any advice on how to use a Fluke >> 80i-1000s connected to a Tek 2465B to display the 120 VAC current >> wave is appreciated in advance. Also, what does "P2 < P1" signify on >> the current probe? > >Alright you guys, a couple of current curve images are now available on >the webpage. For the present case, in regards to the probe's "P2 < P1" >orientation decal, P1 designates Line while P2 indicates Neutral. > The probe provides a sharper, cleaner curve compared to the >resistor. Both curves illustrate how the silicon filament primarily >presents itself as a capacitive load. > The filament's high voltage combined with its low amperage degrades >resistor curve quality. It took a 10 M ohm resistive current sensor for >the half-wave rectification effect to become visible. > The probe curve's mostly blue trace shows the peak-to-peak Line >voltage. It's used to properly trigger the scope. (Perhaps the scope's >line trigger accomplishes the same result with less effort?) The probe >curve's mostly green trace shows the current, with peaks and valleys >created by half-wave rectification at each end of the filament. > The current curve is set to 2mV per division. Does anyone know how >to transpose it to mA? > >Danke, It can't be capacitive. It has no mechanism to store energy. Unless one of the thingies on the end is a cap. A DC curve would resolve that. A thermal image would be interesting too. John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
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| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Date | 2026-04-21 08:54 -0700 |
| Message-ID | <on6fukd6chfua8nm2puqkdc6llb2jbatub@4ax.com> |
| In reply to | #743195 |
On Tue, 21 Apr 2026 08:41:17 -0700, john larkin <jl@glen--canyon.com> wrote: >On Tue, 21 Apr 2026 14:39:14 -0000 (UTC), "Don" <g@crcomp.net> wrote: > >>Don wrote: >>> Recent thread topic transitioned to a tentative opinion on a work-in- >>> progress webpage: >>> >>> <https://crcomp.net/ledfilament/index.php> >>> >>> Radiography imparts interesting insight. Second opinions welcome! >>> The current waveform flopped. Any advice on how to use a Fluke >>> 80i-1000s connected to a Tek 2465B to display the 120 VAC current >>> wave is appreciated in advance. Also, what does "P2 < P1" signify on >>> the current probe? >> >>Alright you guys, a couple of current curve images are now available on >>the webpage. For the present case, in regards to the probe's "P2 < P1" >>orientation decal, P1 designates Line while P2 indicates Neutral. >> The probe provides a sharper, cleaner curve compared to the >>resistor. Both curves illustrate how the silicon filament primarily >>presents itself as a capacitive load. >> The filament's high voltage combined with its low amperage degrades >>resistor curve quality. It took a 10 M ohm resistive current sensor for >>the half-wave rectification effect to become visible. >> The probe curve's mostly blue trace shows the peak-to-peak Line >>voltage. It's used to properly trigger the scope. (Perhaps the scope's >>line trigger accomplishes the same result with less effort?) The probe >>curve's mostly green trace shows the current, with peaks and valleys >>created by half-wave rectification at each end of the filament. >> The current curve is set to 2mV per division. Does anyone know how >>to transpose it to mA? >> >>Danke, > >It can't be capacitive. It has no mechanism to store energy. > >Unless one of the thingies on the end is a cap. A DC curve would >resolve that. > >A thermal image would be interesting too. > > >John Larkin >Highland Tech Glen Canyon Design Center >Lunatic Fringe Electronics No, it lights up with DC, so there's no series cap. John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
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| From | "Don" <g@crcomp.net> |
|---|---|
| Date | 2026-04-21 16:55 +0000 |
| Message-ID | <20260421b@crcomp.net> |
| In reply to | #743196 |
john larkin wrote:
> john larkin wrote:
>> Don wrote:
>>>Don wrote:
>>>> Recent thread topic transitioned to a tentative opinion on a work-in-
>>>> progress webpage:
>>>>
>>>> <https://crcomp.net/ledfilament/index.php>
>>>>
>>>> Radiography imparts interesting insight. Second opinions welcome!
>>>> The current waveform flopped. Any advice on how to use a Fluke
>>>> 80i-1000s connected to a Tek 2465B to display the 120 VAC current
>>>> wave is appreciated in advance. Also, what does "P2 < P1" signify on
>>>> the current probe?
>>>
>>>Alright you guys, a couple of current curve images are now available on
>>>the webpage. For the present case, in regards to the probe's "P2 < P1"
>>>orientation decal, P1 designates Line while P2 indicates Neutral.
>>> The probe provides a sharper, cleaner curve compared to the
>>>resistor. Both curves illustrate how the silicon filament primarily
>>>presents itself as a capacitive load.
>>> The filament's high voltage combined with its low amperage degrades
>>>resistor curve quality. It took a 10 M ohm resistive current sensor for
>>>the half-wave rectification effect to become visible.
>>> The probe curve's mostly blue trace shows the peak-to-peak Line
>>>voltage. It's used to properly trigger the scope. (Perhaps the scope's
>>>line trigger accomplishes the same result with less effort?) The probe
>>>curve's mostly green trace shows the current, with peaks and valleys
>>>created by half-wave rectification at each end of the filament.
>>> The current curve is set to 2mV per division. Does anyone know how
>>>to transpose it to mA?
>>
>>It can't be capacitive. It has no mechanism to store energy.
>>
>>Unless one of the thingies on the end is a cap. A DC curve would
>>resolve that.
>>
>>A thermal image would be interesting too.
>>
> No, it lights up with DC, so there's no series cap.
ELI the ICE man. The trace of the current curve clearly leads the
voltage trace, so the filament must present a capacitive load.
A silicon device that presents a capactive load is different from
a series capacitor:
COB LEDs present capacitive loads through parasitic capacitances
inherent to their densely packed chip-on-board structure. These
capacitances arise between closely spaced LED dies, bonding
wires, and the substrate, affecting driver circuits during
switching.
Danke,
--
73, Don, WD7Q veritas _|_
liberabit |
https://www.qsl.net/wd7q vos |
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| From | Bill Sloman <bill.sloman@ieee.org> |
|---|---|
| Date | 2026-04-22 03:54 +1000 |
| Message-ID | <10s8dkd$1mbf8$1@dont-email.me> |
| In reply to | #743198 |
On 22/04/2026 2:55 am, Don wrote: > john larkin wrote: >> john larkin wrote: >>> Don wrote: >>>> Don wrote: <snip> >> No, it lights up with DC, so there's no series cap. > > ELI the ICE man. The trace of the current curve clearly leads the > voltage trace, so the filament must present a capacitive load. Seems unlikely. It's more likely bad triggering from a not-all-that-closely related waveform. > A silicon device that presents a capacitive load is different from > a series capacitor: > > COB LEDs present capacitive loads through parasitic capacitances > inherent to their densely packed chip-on-board structure. These > capacitances arise between closely spaced LED dies, bonding > wires, and the substrate, affecting driver circuits during > switching. The internal capacitance won't be anything like big enough to show up at mains frequency The likeliest explanation is a bunch of LEDs connected in series with a current limiting resistor between each LED. You'd put in four mains rated diodes to rectify the current going through the LED/resistor string as the applied voltage switched direction. Close to zero and 180 degrees the mains voltage isn't high enough to push any current through the LEDs, but they will start turning on at about 20 degrees, and progressively more of the voltage will get soaked up by the resistors until the voltage peaks at 90 degrees/270 degrees. The LEDs and the resistors will heat up a bit during each half cycle - more in the middle of the string than at the ends, and that will make the current lumpier than you'd expect from a pure sine wave. It won't make much difference to the resistors but LED forward voltage drop is a function of both current and the die temperature, and as the junction gets hotter the forward voltage drops by about 2mV/C The LED/resistor load also going to make current less sinusoidal than the mains supplier would like. -- Bill Sloman, Sydney
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| From | "Don" <g@crcomp.net> |
|---|---|
| Date | 2026-04-21 21:05 +0000 |
| Message-ID | <20260421c@crcomp.net> |
| In reply to | #743207 |
Bill Sloman <bill.sloman@ieee.org> wrote:
> On 22/04/2026 2:55 am, Don wrote:
>> john larkin wrote:
>>> john larkin wrote:
>>>> Don wrote:
>>>>> Don wrote:
>
> <snip>
>
>>> No, it lights up with DC, so there's no series cap.
>>
>> ELI the ICE man. The trace of the current curve clearly leads the
>> voltage trace, so the filament must present a capacitive load.
>
> Seems unlikely. It's more likely bad triggering from a
> not-all-that-closely related waveform.
>
>> A silicon device that presents a capacitive load is different from
>> a series capacitor:
>>
>> COB LEDs present capacitive loads through parasitic capacitances
>> inherent to their densely packed chip-on-board structure. These
>> capacitances arise between closely spaced LED dies, bonding
>> wires, and the substrate, affecting driver circuits during
>> switching.
>
> The internal capacitance won't be anything like big enough to show up at
> mains frequency
>
> The likeliest explanation is a bunch of LEDs connected in series with a
> current limiting resistor between each LED. You'd put in four mains
> rated diodes to rectify the current going through the LED/resistor
> string as the applied voltage switched direction.
>
> Close to zero and 180 degrees the mains voltage isn't high enough to
> push any current through the LEDs, but they will start turning on at
> about 20 degrees, and progressively more of the voltage will get soaked
> up by the resistors until the voltage peaks at 90 degrees/270 degrees.
>
> The LEDs and the resistors will heat up a bit during each half cycle -
> more in the middle of the string than at the ends, and that will make
> the current lumpier than you'd expect from a pure sine wave.
>
> It won't make much difference to the resistors but LED forward voltage
> drop is a function of both current and the die temperature, and as the
> junction gets hotter the forward voltage drops by about 2mV/C
>
> The LED/resistor load also going to make current less sinusoidal than
> the mains supplier would like.
The power factor of cheap COB LED filament can drop to as low as 0.55
leading. [1] A power factor of 0.55 corresponds to a phase angle of
about 56.6 degrees, since PF=cos(θ) and θ=cos−1(0.55).
Looking at the current curves from a different perspective, perhaps
peak polarities are opposite. And a narrow negative peak current only
occurs near the tops of positive peak voltage. This roughly corresponds
to Oscillogram 2. [2]
Note.
[1] <https://blog.1000bulbs.com/home/power-factor-explained>
[2] <https://shuttlelighting.com/the-electrical-and-dimming-behaviour-of-led-filament-lamps/>
Danke,
--
73, Don, WD7Q veritas _|_
liberabit |
https://www.qsl.net/wd7q vos |
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| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Date | 2026-04-21 17:03 -0700 |
| Message-ID | <1p3gukdnd6do8m9st1vj2upos5tp8cg43v@4ax.com> |
| In reply to | #743216 |
On Tue, 21 Apr 2026 21:05:40 -0000 (UTC), "Don" <g@crcomp.net> wrote: >Bill Sloman <bill.sloman@ieee.org> wrote: >> On 22/04/2026 2:55 am, Don wrote: >>> john larkin wrote: >>>> john larkin wrote: >>>>> Don wrote: >>>>>> Don wrote: >> >> <snip> >> >>>> No, it lights up with DC, so there's no series cap. >>> >>> ELI the ICE man. The trace of the current curve clearly leads the >>> voltage trace, so the filament must present a capacitive load. >> >> Seems unlikely. It's more likely bad triggering from a >> not-all-that-closely related waveform. >> >>> A silicon device that presents a capacitive load is different from >>> a series capacitor: >>> >>> COB LEDs present capacitive loads through parasitic capacitances >>> inherent to their densely packed chip-on-board structure. These >>> capacitances arise between closely spaced LED dies, bonding >>> wires, and the substrate, affecting driver circuits during >>> switching. >> >> The internal capacitance won't be anything like big enough to show up at >> mains frequency >> >> The likeliest explanation is a bunch of LEDs connected in series with a >> current limiting resistor between each LED. You'd put in four mains >> rated diodes to rectify the current going through the LED/resistor >> string as the applied voltage switched direction. >> >> Close to zero and 180 degrees the mains voltage isn't high enough to >> push any current through the LEDs, but they will start turning on at >> about 20 degrees, and progressively more of the voltage will get soaked >> up by the resistors until the voltage peaks at 90 degrees/270 degrees. >> >> The LEDs and the resistors will heat up a bit during each half cycle - >> more in the middle of the string than at the ends, and that will make >> the current lumpier than you'd expect from a pure sine wave. >> >> It won't make much difference to the resistors but LED forward voltage >> drop is a function of both current and the die temperature, and as the >> junction gets hotter the forward voltage drops by about 2mV/C >> >> The LED/resistor load also going to make current less sinusoidal than >> the mains supplier would like. > >The power factor of cheap COB LED filament can drop to as low as 0.55 >leading. [1] A power factor of 0.55 corresponds to a phase angle of >about 56.6 degrees, since PF=cos?(?) and ?=cos??1(0.55). Power factor has a diffferent meaning for nonlinear loads; it doesn't necessarily mean phase shift. I have one official document that says PF is undefined for non-sinusoidal loads. One common practice is to say that PF = real watts / (RMS volts * RMS amps) > >Looking at the current curves from a different perspective, perhaps >peak polarities are opposite. And a narrow negative peak current only >occurs near the tops of positive peak voltage. This roughly corresponds >to Oscillogram 2. [2] > >Note. > >[1] <https://blog.1000bulbs.com/home/power-factor-explained> >[2] <https://shuttlelighting.com/the-electrical-and-dimming-behaviour-of-led-filament-lamps/> > >Danke, John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
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| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Date | 2026-04-21 12:26 -0700 |
| Message-ID | <jkjfuk5hchs2eueqvbmlco2kioggg2lj7a@4ax.com> |
| In reply to | #743198 |
On Tue, 21 Apr 2026 16:55:37 -0000 (UTC), "Don" <g@crcomp.net> wrote: >john larkin wrote: >> john larkin wrote: >>> Don wrote: >>>>Don wrote: >>>>> Recent thread topic transitioned to a tentative opinion on a work-in- >>>>> progress webpage: >>>>> >>>>> <https://crcomp.net/ledfilament/index.php> >>>>> >>>>> Radiography imparts interesting insight. Second opinions welcome! >>>>> The current waveform flopped. Any advice on how to use a Fluke >>>>> 80i-1000s connected to a Tek 2465B to display the 120 VAC current >>>>> wave is appreciated in advance. Also, what does "P2 < P1" signify on >>>>> the current probe? >>>> >>>>Alright you guys, a couple of current curve images are now available on >>>>the webpage. For the present case, in regards to the probe's "P2 < P1" >>>>orientation decal, P1 designates Line while P2 indicates Neutral. >>>> The probe provides a sharper, cleaner curve compared to the >>>>resistor. Both curves illustrate how the silicon filament primarily >>>>presents itself as a capacitive load. >>>> The filament's high voltage combined with its low amperage degrades >>>>resistor curve quality. It took a 10 M ohm resistive current sensor for >>>>the half-wave rectification effect to become visible. >>>> The probe curve's mostly blue trace shows the peak-to-peak Line >>>>voltage. It's used to properly trigger the scope. (Perhaps the scope's >>>>line trigger accomplishes the same result with less effort?) The probe >>>>curve's mostly green trace shows the current, with peaks and valleys >>>>created by half-wave rectification at each end of the filament. >>>> The current curve is set to 2mV per division. Does anyone know how >>>>to transpose it to mA? >>> >>>It can't be capacitive. It has no mechanism to store energy. >>> >>>Unless one of the thingies on the end is a cap. A DC curve would >>>resolve that. >>> >>>A thermal image would be interesting too. >>> >> No, it lights up with DC, so there's no series cap. > >ELI the ICE man. The trace of the current curve clearly leads the >voltage trace, so the filament must present a capacitive load. > A silicon device that presents a capactive load is different from >a series capacitor: > > COB LEDs present capacitive loads through parasitic capacitances > inherent to their densely packed chip-on-board structure. These > capacitances arise between closely spaced LED dies, bonding > wires, and the substrate, affecting driver circuits during > switching. > >Danke, Since the current probe waveform is so different from the one that uses a resistor, one must be wrong, or likely both. Stray capacitances are at least six orders of magnitude from causing the phase shift that you are seeing. John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
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| From | "Don" <g@crcomp.net> |
|---|---|
| Date | 2026-04-22 01:44 +0000 |
| Message-ID | <20260421d@crcomp.net> |
| In reply to | #743211 |
john larkin wrote:
> Don wrote:
>>john larkin wrote:
>>> john larkin wrote:
>>>> Don wrote:
>>>>>Don wrote:
>>>>>> Recent thread topic transitioned to a tentative opinion on a work-in-
>>>>>> progress webpage:
>>>>>>
>>>>>> <https://crcomp.net/ledfilament/index.php>
>>>>>>
>>>>>> Radiography imparts interesting insight. Second opinions welcome!
>>>>>> The current waveform flopped. Any advice on how to use a Fluke
>>>>>> 80i-1000s connected to a Tek 2465B to display the 120 VAC current
>>>>>> wave is appreciated in advance. Also, what does "P2 < P1" signify on
>>>>>> the current probe?
>>>>>
>>>>>Alright you guys, a couple of current curve images are now available on
>>>>>the webpage. For the present case, in regards to the probe's "P2 < P1"
>>>>>orientation decal, P1 designates Line while P2 indicates Neutral.
>>>>> The probe provides a sharper, cleaner curve compared to the
>>>>>resistor. Both curves illustrate how the silicon filament primarily
>>>>>presents itself as a capacitive load.
>>>>> The filament's high voltage combined with its low amperage degrades
>>>>>resistor curve quality. It took a 10 M ohm resistive current sensor for
>>>>>the half-wave rectification effect to become visible.
>>>>> The probe curve's mostly blue trace shows the peak-to-peak Line
>>>>>voltage. It's used to properly trigger the scope. (Perhaps the scope's
>>>>>line trigger accomplishes the same result with less effort?) The probe
>>>>>curve's mostly green trace shows the current, with peaks and valleys
>>>>>created by half-wave rectification at each end of the filament.
>>>>> The current curve is set to 2mV per division. Does anyone know how
>>>>>to transpose it to mA?
>>>>
>>>>It can't be capacitive. It has no mechanism to store energy.
>>>>
>>>>Unless one of the thingies on the end is a cap. A DC curve would
>>>>resolve that.
>>>>
>>>>A thermal image would be interesting too.
>>>>
>>> No, it lights up with DC, so there's no series cap.
>>
>>ELI the ICE man. The trace of the current curve clearly leads the
>>voltage trace, so the filament must present a capacitive load.
>> A silicon device that presents a capactive load is different from
>>a series capacitor:
>>
>> COB LEDs present capacitive loads through parasitic capacitances
>> inherent to their densely packed chip-on-board structure. These
>> capacitances arise between closely spaced LED dies, bonding
>> wires, and the substrate, affecting driver circuits during
>> switching.
>
> Since the current probe waveform is so different from the one that
> uses a resistor, one must be wrong, or likely both.
>
> Stray capacitances are at least six orders of magnitude from causing
> the phase shift that you are seeing.
For what it's worth, my own expectations were subverted when the current
curve indicated a non-resistive load. So, this thread tries to resolve
the discrepancy.
In my experience, the 320 Vp-p 1 mA combo crushes the current
sensing resistor idea. It took a 10 M-ohm resistor in series with the
CoB LED to see anything other than a ~320 Vp-p waveform across the so-
called sensing resistor.
Connecting a current sensing probe to an oscilloscope is even easier
than inserting a resistor in series with a CoB LED. Yet given the
unknown meaning of the "P2 > P1" decal on the probe, it's plausible for
the probe to be connected backwards. This oscillogram depicts a probe
reversal:
<https://crcomp.net/ledfilament/curveprobe2.png>
Danke,
--
73, Don, WD7Q veritas _|_
liberabit |
https://www.qsl.net/wd7q vos |
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| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Date | 2026-04-21 19:16 -0700 |
| Message-ID | <qobgukd7m71fnbh3fvjdm9ok4eda8kgibj@4ax.com> |
| In reply to | #743219 |
On Wed, 22 Apr 2026 01:44:12 -0000 (UTC), "Don" <g@crcomp.net> wrote: >john larkin wrote: >> Don wrote: >>>john larkin wrote: >>>> john larkin wrote: >>>>> Don wrote: >>>>>>Don wrote: >>>>>>> Recent thread topic transitioned to a tentative opinion on a work-in- >>>>>>> progress webpage: >>>>>>> >>>>>>> <https://crcomp.net/ledfilament/index.php> >>>>>>> >>>>>>> Radiography imparts interesting insight. Second opinions welcome! >>>>>>> The current waveform flopped. Any advice on how to use a Fluke >>>>>>> 80i-1000s connected to a Tek 2465B to display the 120 VAC current >>>>>>> wave is appreciated in advance. Also, what does "P2 < P1" signify on >>>>>>> the current probe? >>>>>> >>>>>>Alright you guys, a couple of current curve images are now available on >>>>>>the webpage. For the present case, in regards to the probe's "P2 < P1" >>>>>>orientation decal, P1 designates Line while P2 indicates Neutral. >>>>>> The probe provides a sharper, cleaner curve compared to the >>>>>>resistor. Both curves illustrate how the silicon filament primarily >>>>>>presents itself as a capacitive load. >>>>>> The filament's high voltage combined with its low amperage degrades >>>>>>resistor curve quality. It took a 10 M ohm resistive current sensor for >>>>>>the half-wave rectification effect to become visible. >>>>>> The probe curve's mostly blue trace shows the peak-to-peak Line >>>>>>voltage. It's used to properly trigger the scope. (Perhaps the scope's >>>>>>line trigger accomplishes the same result with less effort?) The probe >>>>>>curve's mostly green trace shows the current, with peaks and valleys >>>>>>created by half-wave rectification at each end of the filament. >>>>>> The current curve is set to 2mV per division. Does anyone know how >>>>>>to transpose it to mA? >>>>> >>>>>It can't be capacitive. It has no mechanism to store energy. >>>>> >>>>>Unless one of the thingies on the end is a cap. A DC curve would >>>>>resolve that. >>>>> >>>>>A thermal image would be interesting too. >>>>> >>>> No, it lights up with DC, so there's no series cap. >>> >>>ELI the ICE man. The trace of the current curve clearly leads the >>>voltage trace, so the filament must present a capacitive load. >>> A silicon device that presents a capactive load is different from >>>a series capacitor: >>> >>> COB LEDs present capacitive loads through parasitic capacitances >>> inherent to their densely packed chip-on-board structure. These >>> capacitances arise between closely spaced LED dies, bonding >>> wires, and the substrate, affecting driver circuits during >>> switching. >> >> Since the current probe waveform is so different from the one that >> uses a resistor, one must be wrong, or likely both. >> >> Stray capacitances are at least six orders of magnitude from causing >> the phase shift that you are seeing. > >For what it's worth, my own expectations were subverted when the current >curve indicated a non-resistive load. So, this thread tries to resolve >the discrepancy. > In my experience, the 320 Vp-p 1 mA combo crushes the current >sensing resistor idea. It took a 10 M-ohm resistor in series with the >CoB LED to see anything other than a ~320 Vp-p waveform across the so- >called sensing resistor. > Connecting a current sensing probe to an oscilloscope is even easier >than inserting a resistor in series with a CoB LED. Yet given the >unknown meaning of the "P2 > P1" decal on the probe, it's plausible for >the probe to be connected backwards. This oscillogram depicts a probe >reversal: > > <https://crcomp.net/ledfilament/curveprobe2.png> > >Danke, A reasonable current sense resistor might be 10 or 100 ohms. John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
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| From | "Don" <g@crcomp.net> |
|---|---|
| Date | 2026-04-24 13:37 +0000 |
| Message-ID | <20260424a@crcomp.net> |
| In reply to | #743211 |
john larkin wrote:
> Don wrote:
>>john larkin wrote:
>>> john larkin wrote:
>>>> Don wrote:
>>>>>Don wrote:
>>>>>> Recent thread topic transitioned to a tentative opinion on a work-in-
>>>>>> progress webpage:
>>>>>>
>>>>>> <https://crcomp.net/ledfilament/index.php>
>>>>>>
>>>>>> Radiography imparts interesting insight. Second opinions welcome!
>>>>>> The current waveform flopped. Any advice on how to use a Fluke
>>>>>> 80i-1000s connected to a Tek 2465B to display the 120 VAC current
>>>>>> wave is appreciated in advance. Also, what does "P2 < P1" signify on
>>>>>> the current probe?
>>>>>
>>>>>Alright you guys, a couple of current curve images are now available on
>>>>>the webpage. For the present case, in regards to the probe's "P2 < P1"
>>>>>orientation decal, P1 designates Line while P2 indicates Neutral.
>>>>> The probe provides a sharper, cleaner curve compared to the
>>>>>resistor. Both curves illustrate how the silicon filament primarily
>>>>>presents itself as a capacitive load.
>>>>> The filament's high voltage combined with its low amperage degrades
>>>>>resistor curve quality. It took a 10 M ohm resistive current sensor for
>>>>>the half-wave rectification effect to become visible.
>>>>> The probe curve's mostly blue trace shows the peak-to-peak Line
>>>>>voltage. It's used to properly trigger the scope. (Perhaps the scope's
>>>>>line trigger accomplishes the same result with less effort?) The probe
>>>>>curve's mostly green trace shows the current, with peaks and valleys
>>>>>created by half-wave rectification at each end of the filament.
>>>>> The current curve is set to 2mV per division. Does anyone know how
>>>>>to transpose it to mA?
>>>>
>>>>It can't be capacitive. It has no mechanism to store energy.
>>>>
>>>>Unless one of the thingies on the end is a cap. A DC curve would
>>>>resolve that.
>>>>
>>>>A thermal image would be interesting too.
>>>>
>>> No, it lights up with DC, so there's no series cap.
>>
>>ELI the ICE man. The trace of the current curve clearly leads the
>>voltage trace, so the filament must present a capacitive load.
>> A silicon device that presents a capactive load is different from
>>a series capacitor:
>>
>> COB LEDs present capacitive loads through parasitic capacitances
>> inherent to their densely packed chip-on-board structure. These
>> capacitances arise between closely spaced LED dies, bonding
>> wires, and the substrate, affecting driver circuits during
>> switching.
>
> Since the current probe waveform is so different from the one that
> uses a resistor, one must be wrong, or likely both.
>
> Stray capacitances are at least six orders of magnitude from causing
> the phase shift that you are seeing.
You're wrong, no doubt about it. Stray capacitance caused my problem.
And your sweeping generality at this juncture led me to question my
correct quantitative instincts.
"ELI the ICE man. The trace of the current curve clearly leads the
voltage trace" leads to the correct solution.
Hint: stray capacitance originates from more than one source.
Danke,
--
73, Don, WD7Q veritas _|_
liberabit |
https://www.qsl.net/wd7q vos |
[toc] | [prev] | [next] | [standalone]
| From | john larkin <jl@glen--canyon.com> |
|---|---|
| Date | 2026-04-24 07:55 -0700 |
| Message-ID | <rl0nukdg28kug1ncquik61iqb06ak4gtld@4ax.com> |
| In reply to | #743301 |
On Fri, 24 Apr 2026 13:37:43 -0000 (UTC), "Don" <g@crcomp.net> wrote: >john larkin wrote: >> Don wrote: >>>john larkin wrote: >>>> john larkin wrote: >>>>> Don wrote: >>>>>>Don wrote: >>>>>>> Recent thread topic transitioned to a tentative opinion on a work-in- >>>>>>> progress webpage: >>>>>>> >>>>>>> <https://crcomp.net/ledfilament/index.php> >>>>>>> >>>>>>> Radiography imparts interesting insight. Second opinions welcome! >>>>>>> The current waveform flopped. Any advice on how to use a Fluke >>>>>>> 80i-1000s connected to a Tek 2465B to display the 120 VAC current >>>>>>> wave is appreciated in advance. Also, what does "P2 < P1" signify on >>>>>>> the current probe? >>>>>> >>>>>>Alright you guys, a couple of current curve images are now available on >>>>>>the webpage. For the present case, in regards to the probe's "P2 < P1" >>>>>>orientation decal, P1 designates Line while P2 indicates Neutral. >>>>>> The probe provides a sharper, cleaner curve compared to the >>>>>>resistor. Both curves illustrate how the silicon filament primarily >>>>>>presents itself as a capacitive load. >>>>>> The filament's high voltage combined with its low amperage degrades >>>>>>resistor curve quality. It took a 10 M ohm resistive current sensor for >>>>>>the half-wave rectification effect to become visible. >>>>>> The probe curve's mostly blue trace shows the peak-to-peak Line >>>>>>voltage. It's used to properly trigger the scope. (Perhaps the scope's >>>>>>line trigger accomplishes the same result with less effort?) The probe >>>>>>curve's mostly green trace shows the current, with peaks and valleys >>>>>>created by half-wave rectification at each end of the filament. >>>>>> The current curve is set to 2mV per division. Does anyone know how >>>>>>to transpose it to mA? >>>>> >>>>>It can't be capacitive. It has no mechanism to store energy. >>>>> >>>>>Unless one of the thingies on the end is a cap. A DC curve would >>>>>resolve that. >>>>> >>>>>A thermal image would be interesting too. >>>>> >>>> No, it lights up with DC, so there's no series cap. >>> >>>ELI the ICE man. The trace of the current curve clearly leads the >>>voltage trace, so the filament must present a capacitive load. >>> A silicon device that presents a capactive load is different from >>>a series capacitor: >>> >>> COB LEDs present capacitive loads through parasitic capacitances >>> inherent to their densely packed chip-on-board structure. These >>> capacitances arise between closely spaced LED dies, bonding >>> wires, and the substrate, affecting driver circuits during >>> switching. >> >> Since the current probe waveform is so different from the one that >> uses a resistor, one must be wrong, or likely both. >> >> Stray capacitances are at least six orders of magnitude from causing >> the phase shift that you are seeing. > >You're wrong, no doubt about it. Stray capacitance caused my problem. >And your sweeping generality at this juncture led me to question my >correct quantitative instincts. > >"ELI the ICE man. The trace of the current curve clearly leads the >voltage trace" leads to the correct solution. > >Hint: stray capacitance originates from more than one source. > >Danke, Probably the biggest capacitance is the LEDs themselves. If you used a sensible value current shunt resistor - ohms and not megohms - the effects of the capacitance would be invisible with 60 Hz excitation. Measure the capacitance and do the math. Or Spice it. "ELI the ICE man" is not quantitative. John Larkin Highland Tech Glen Canyon Design Center Lunatic Fringe Electronics
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