I have a cheap torch (US: flashlight) which has three AAA cells in series powering nine white LEDs in parallel, nothing else that I can see. I guess the current is limited by the battery impedance. One LED is off, four are on, three flashing at about 15Hz and one flashes every few seconds. I suppose when on, the current draw is sufficient to drop the battery voltage, the three LEDs go off and the battery recovers. Good enough for a US patent anyway. Cheers -- Syd
Low component count relaxation oscillator
Started by ●May 29, 2015
Reply by ●May 29, 20152015-05-29
On 05/29/2015 12:21 PM, Syd Rumpo wrote:> I have a cheap torch (US: flashlight) which has three AAA cells in > series powering nine white LEDs in parallel, nothing else that I can > see. I guess the current is limited by the battery impedance. > > One LED is off, four are on, three flashing at about 15Hz and one > flashes every few seconds. > > I suppose when on, the current draw is sufficient to drop the battery > voltage, the three LEDs go off and the battery recovers. > > Good enough for a US patent anyway. > > CheersInteresting. I suppose it's the thermal feedback that makes it oscillate--battery recovers, LED starts to conduct, LED forward voltage drops, current increases, battery droops, LED stops conducting, LED cools down, .... Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Reply by ●May 29, 20152015-05-29
On Fri, 29 May 2015 17:21:35 +0100, Syd Rumpo <usenet@nononono.co.uk> wrote:>I have a cheap torch (US: flashlight) which has three AAA cells in >series powering nine white LEDs in parallel, nothing else that I can >see. I guess the current is limited by the battery impedance. > >One LED is off, four are on, three flashing at about 15Hz and one >flashes every few seconds. > >I suppose when on, the current draw is sufficient to drop the battery >voltage, the three LEDs go off and the battery recovers. > >Good enough for a US patent anyway. > >CheersIt's not that uncommon for simple LEDs to flash, by themselves, at a few Hz. I suspect flakey wire bonds. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 29, 20152015-05-29
On 29/05/2015 17:53, John Larkin wrote:> On Fri, 29 May 2015 17:21:35 +0100, Syd Rumpo <usenet@nononono.co.uk> > wrote: > >> I have a cheap torch (US: flashlight) which has three AAA cells in >> series powering nine white LEDs in parallel, nothing else that I can >> see. I guess the current is limited by the battery impedance. >> >> One LED is off, four are on, three flashing at about 15Hz and one >> flashes every few seconds. >> >> I suppose when on, the current draw is sufficient to drop the battery >> voltage, the three LEDs go off and the battery recovers. >> >> Good enough for a US patent anyway. >> >> Cheers > > It's not that uncommon for simple LEDs to flash, by themselves, at a > few Hz. I suspect flakey wire bonds.But probably not on three out of nine LEDs. Just turned it on again, and only one flashes. After a few seconds it's two. Now it's back to three and one occasionally, but there's a clear mark/space ratio difference between the three. Maybe it's been taken over by aliens, has mistaken me for Skybuck, and is trying to communicate. Cheers -- Syd
Reply by ●May 29, 20152015-05-29
On Friday, May 29, 2015 at 2:30:07 PM UTC-4, Syd Rumpo wrote:> On 29/05/2015 17:53, John Larkin wrote: > > On Fri, 29 May 2015 17:21:35 +0100, Syd Rumpo <usenet@nononono.co.uk> > > wrote: > > > >> I have a cheap torch (US: flashlight) which has three AAA cells in > >> series powering nine white LEDs in parallel, nothing else that I can > >> see. I guess the current is limited by the battery impedance. > >> > >> One LED is off, four are on, three flashing at about 15Hz and one > >> flashes every few seconds. > >> > >> I suppose when on, the current draw is sufficient to drop the battery > >> voltage, the three LEDs go off and the battery recovers. > >> > >> Good enough for a US patent anyway. > >> > >> Cheers > > > > It's not that uncommon for simple LEDs to flash, by themselves, at a > > few Hz. I suspect flakey wire bonds. > > But probably not on three out of nine LEDs. > > Just turned it on again, and only one flashes. After a few seconds it's > two. Now it's back to three and one occasionally, but there's a clear > mark/space ratio difference between the three. > > Maybe it's been taken over by aliens, has mistaken me for Skybuck, and > is trying to communicate.If so, do NOT let it get close to your gaming computer. It'll explode. Again. :-) Cheers, James Arthur
Reply by ●May 29, 20152015-05-29
On Fri, 29 May 2015 12:52:46 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 05/29/2015 12:21 PM, Syd Rumpo wrote: >> I have a cheap torch (US: flashlight) which has three AAA cells in >> series powering nine white LEDs in parallel, nothing else that I can >> see. I guess the current is limited by the battery impedance. >> >> One LED is off, four are on, three flashing at about 15Hz and one >> flashes every few seconds. >> >> I suppose when on, the current draw is sufficient to drop the battery >> voltage, the three LEDs go off and the battery recovers. >> >> Good enough for a US patent anyway. >> >> Cheers > >Interesting. I suppose it's the thermal feedback that makes it >oscillate--battery recovers, LED starts to conduct, LED forward voltage >drops, current increases, battery droops, LED stops conducting, LED >cools down, .... > >Cheers > >Phil HobbsI've got an otherwise nice Lee Valley LED flashlight that has one LED that flashes at maybe 2Hz. (B) here: http://www.leevalley.com/en/images/item/Gardening/67k7445s1.jpg I don't think it's a coincidence that it's the one in the center of the array. -- Best regards, Spehro Pefhany Amazon link for AoE 3rd Edition: http://tinyurl.com/ntrpwu8 Microchip link for 2015 Masters in Phoenix: http://tinyurl.com/l7g2k48
Reply by ●May 29, 20152015-05-29
On Fri, 29 May 2015 18:36:46 -0400, Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:>On Fri, 29 May 2015 12:52:46 -0400, Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote: > >>On 05/29/2015 12:21 PM, Syd Rumpo wrote: >>> I have a cheap torch (US: flashlight) which has three AAA cells in >>> series powering nine white LEDs in parallel, nothing else that I can >>> see. I guess the current is limited by the battery impedance. >>> >>> One LED is off, four are on, three flashing at about 15Hz and one >>> flashes every few seconds. >>> >>> I suppose when on, the current draw is sufficient to drop the battery >>> voltage, the three LEDs go off and the battery recovers. >>> >>> Good enough for a US patent anyway. >>> >>> Cheers >> >>Interesting. I suppose it's the thermal feedback that makes it >>oscillate--battery recovers, LED starts to conduct, LED forward voltage >>drops, current increases, battery droops, LED stops conducting, LED >>cools down, .... >> >>Cheers >> >>Phil Hobbs > >I've got an otherwise nice Lee Valley LED flashlight that has one LED >that flashes at maybe 2Hz. (B) here: > >http://www.leevalley.com/en/images/item/Gardening/67k7445s1.jpg > >I don't think it's a coincidence that it's the one in the center of >the array.There seems to be an actual LED flashing failure mode. I can't imagine what the physics could be. It happened on my Mantis, which has a bunch of serial-parallel LEDs. I see it on traffic lights, usually the green light. One section of LEDs dies, and occasionally blinks. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●May 29, 20152015-05-29
In article <mka3k7$gqn$1@dont-email.me>, usenet@nononono.co.uk says...> > I have a cheap torch (US: flashlight) which has three AAA cells in > series powering nine white LEDs in parallel, nothing else that I can > see. I guess the current is limited by the battery impedance. > > One LED is off, four are on, three flashing at about 15Hz and one > flashes every few seconds. > > I suppose when on, the current draw is sufficient to drop the battery > voltage, the three LEDs go off and the battery recovers. > > Good enough for a US patent anyway. > > CheersOk, I took note the word "Cheap" and then "US: flashlight", does that mean we make junk? The last time I checked, we don't make anything, anymore ;) Jamie
Reply by ●May 29, 20152015-05-29
On Friday, May 29, 2015 at 6:35:20 PM UTC-4, Spehro Pefhany wrote:> On Fri, 29 May 2015 12:52:46 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > > >On 05/29/2015 12:21 PM, Syd Rumpo wrote: > >> I have a cheap torch (US: flashlight) which has three AAA cells in > >> series powering nine white LEDs in parallel, nothing else that I can > >> see. I guess the current is limited by the battery impedance. > >> > >> One LED is off, four are on, three flashing at about 15Hz and one > >> flashes every few seconds. > >> > >> I suppose when on, the current draw is sufficient to drop the battery > >> voltage, the three LEDs go off and the battery recovers. > >> > >> Good enough for a US patent anyway. > >> > >> Cheers > > > >Interesting. I suppose it's the thermal feedback that makes it > >oscillate--battery recovers, LED starts to conduct, LED forward voltage > >drops, current increases, battery droops, LED stops conducting, LED > >cools down, .... > > > >Cheers > > > >Phil Hobbs > > I've got an otherwise nice Lee Valley LED flashlight that has one LED > that flashes at maybe 2Hz. (B) here: > > http://www.leevalley.com/en/images/item/Gardening/67k7445s1.jpg > > I don't think it's a coincidence that it's the one in the center of > the array. >Why the middle? Given Phil's thermal model, an led near the edge might have see more temperature change. (maybe you have a different idea?) Led's in series would be nice, if you could make them fail as a short. George H.> > > -- > Best regards, > Spehro Pefhany > Amazon link for AoE 3rd Edition: http://tinyurl.com/ntrpwu8 > Microchip link for 2015 Masters in Phoenix: http://tinyurl.com/l7g2k48
Reply by ●May 30, 20152015-05-30
In article <9ashmalsl3vmrnkvcsb3fp0f54gbsrc15m@4ax.com>, John Larkin <jlarkin@highlandtechnology.com> wrote:> On Fri, 29 May 2015 18:36:46 -0400, Spehro Pefhany > <speffSNIP@interlogDOTyou.knowwhat> wrote: > > >On Fri, 29 May 2015 12:52:46 -0400, Phil Hobbs > ><pcdhSpamMeSenseless@electrooptical.net> wrote: > > > >>On 05/29/2015 12:21 PM, Syd Rumpo wrote: > >>> I have a cheap torch (US: flashlight) which has three AAA cells in > >>> series powering nine white LEDs in parallel, nothing else that I can > >>> see. I guess the current is limited by the battery impedance. > >>> > >>> One LED is off, four are on, three flashing at about 15Hz and one > >>> flashes every few seconds. > >>> > >>> I suppose when on, the current draw is sufficient to drop the battery > >>> voltage, the three LEDs go off and the battery recovers. > >>> > >>> Good enough for a US patent anyway. > >>> > >>> Cheers > >> > >>Interesting. I suppose it's the thermal feedback that makes it > >>oscillate--battery recovers, LED starts to conduct, LED forward voltage > >>drops, current increases, battery droops, LED stops conducting, LED > >>cools down, .... > >> > >>Cheers > >> > >>Phil Hobbs > > > >I've got an otherwise nice Lee Valley LED flashlight that has one LED > >that flashes at maybe 2Hz. (B) here: > > > >http://www.leevalley.com/en/images/item/Gardening/67k7445s1.jpg > > > >I don't think it's a coincidence that it's the one in the center of > >the array. > > There seems to be an actual LED flashing failure mode. I can't imagine > what the physics could be. > > It happened on my Mantis, which has a bunch of serial-parallel LEDs. > > I see it on traffic lights, usually the green light. One section of > LEDs dies, and occasionally blinks.The LED chip is probably slowly arcing itself away after ESD damage. Some green, blue, and violet chips are crazy sensitive. And no, you can't make a relaxation oscillator using a battery and a hot LED. The impedance of the battery is much too high for the 0.1V change per LED to matter. It can be done with an ultracapacitor but that's expensive. -- I will not see posts from astraweb, theremailer, dizum, or google because they host Usenet flooders.
