Forums

Low component count relaxation oscillator

Started by Syd Rumpo May 29, 2015
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
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 -- 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
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. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
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
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
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. -- 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
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
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. > > Cheers
Ok, 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
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
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.