On Tue, 12 Apr 2011 14:36:56 -0700 John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in Message id: <ieh9q69rimlkhefemkl0b26pk1ofoiee23@4ax.com>:>On Tue, 12 Apr 2011 12:34:54 -0700, AES <siegman@stanford.edu> wrote: > >>> > Is there any hidden connection between the insistence of these LEDs on >>> > continuing to emit light long after they've been turned off, and the >>> > insistence of the participants in this thread in continuing to re-emit >>> > screenfuls and screenfuls of previous posts, before finally adding a >>> > one-sentence comment at the end?!?!?! >> >> >>> Modern newsreaders often run on machines with LED backlights? ;) >>> Cheers, Phil Hobbs >> >>This thread really has been off the charts in the unwillingness of >>posters to trim out unnecessary cruft when they reply! > >Get some scroll bars. They're not expensive. >Even easier if you're using Agent and perhaps other newsreaders. Use your scroll wheel. One click will page down.
LED on Photodiode step response
Started by ●April 11, 2011
Reply by ●April 13, 20112011-04-13
Reply by ●April 13, 20112011-04-13
On a sunny day (Wed, 13 Apr 2011 05:55:39 -0400) it happened JW <none@dev.null> wrote in <8lsaq617hufrla3jai1vhcp9qd08hop2qp@4ax.com>:>Even easier if you're using Agent and perhaps other newsreaders. Use your >scroll wheel. One click will page down.Yes, works in NewsFleX (Linux) too.
Reply by ●April 13, 20112011-04-13
On Wed, 13 Apr 2011 05:55:39 -0400, JW <none@dev.null> wrote:>On Tue, 12 Apr 2011 14:36:56 -0700 John Larkin ><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in Message id: ><ieh9q69rimlkhefemkl0b26pk1ofoiee23@4ax.com>: > >>On Tue, 12 Apr 2011 12:34:54 -0700, AES <siegman@stanford.edu> wrote: >> >>>> > Is there any hidden connection between the insistence of these LEDs on >>>> > continuing to emit light long after they've been turned off, and the >>>> > insistence of the participants in this thread in continuing to re-emit >>>> > screenfuls and screenfuls of previous posts, before finally adding a >>>> > one-sentence comment at the end?!?!?! >>> >>> >>>> Modern newsreaders often run on machines with LED backlights? ;) >>>> Cheers, Phil Hobbs >>> >>>This thread really has been off the charts in the unwillingness of >>>posters to trim out unnecessary cruft when they reply! >> >>Get some scroll bars. They're not expensive. >> > >Even easier if you're using Agent and perhaps other newsreaders. Use your >scroll wheel. One click will page down.The only thing worse than the Usenet pussy you responded to is your Usenet pussy response. The 'cruft' that needs trimming is you pussified, brainless fucktards.
Reply by ●April 13, 20112011-04-13
On Wed, 13 Apr 2011 10:49:40 GMT, Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:>On a sunny day (Wed, 13 Apr 2011 05:55:39 -0400) it happened JW ><none@dev.null> wrote in <8lsaq617hufrla3jai1vhcp9qd08hop2qp@4ax.com>: > >>Even easier if you're using Agent and perhaps other newsreaders. Use your >>scroll wheel. One click will page down. > >Yes, works in NewsFleX (Linux) too.Stupid children like you three should not be allowed on computers. There should be an aptitude requirement. None of you three would qualify. It doesn't get much more pathetic than this stupid shit.
Reply by ●April 13, 20112011-04-13
On a sunny day (Wed, 13 Apr 2011 04:13:04 -0700) it happened Bart! <B@rt_The_Sheriff_Is_A_Nig***!.org> wrote in <t41bq6lu6ff18ds4o7p595kpkjf7rao8rr@4ax.com>:>It doesn't get much more pathetic than this stupid shit.Then why do you write it?
Reply by ●April 13, 20112011-04-13
On Wed, 13 Apr 2011 11:41:50 GMT, Jan Panteltje <pNaonStpealmtje@yahoo.com> wrote:>On a sunny day (Wed, 13 Apr 2011 04:13:04 -0700) it happened Bart! ><B@rt_The_Sheriff_Is_A_Nig***!.org> wrote in ><t41bq6lu6ff18ds4o7p595kpkjf7rao8rr@4ax.com>: >>It doesn't get much more pathetic than this stupid shit. > >Then why do you write it?English not your first language, dumbfuck?
Reply by ●April 13, 20112011-04-13
On a sunny day (Wed, 13 Apr 2011 04:51:23 -0700) it happened Bart! <B@rt_The_Sheriff_Is_A_Nig***!.org> wrote in <0h3bq6tu8ldr8jrdh8pcval71bqnrvkv17@4ax.com>:>On Wed, 13 Apr 2011 11:41:50 GMT, Jan Panteltje ><pNaonStpealmtje@yahoo.com> wrote: > >>On a sunny day (Wed, 13 Apr 2011 04:13:04 -0700) it happened Bart! >><B@rt_The_Sheriff_Is_A_Nig***!.org> wrote in >><t41bq6lu6ff18ds4o7p595kpkjf7rao8rr@4ax.com>: >>>It doesn't get much more pathetic than this stupid shit. >> >>Then why do you write it? > > English not your first language, dumbfuck?And now you write shit again, why bother? You know nothing better?
Reply by ●April 13, 20112011-04-13
On Wed, 13 Apr 2011 04:10:03 -0700 Bart! <B@rt_The_Sheriff_Is_A_Nig***!.org> wrote in Message id: <5v0bq6d228v3hnl0k3heb672dslmdp6a0o@4ax.com>:>On Wed, 13 Apr 2011 05:55:39 -0400, JW <none@dev.null> wrote: > >>On Tue, 12 Apr 2011 14:36:56 -0700 John Larkin >><jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in Message id: >><ieh9q69rimlkhefemkl0b26pk1ofoiee23@4ax.com>: >> >>>On Tue, 12 Apr 2011 12:34:54 -0700, AES <siegman@stanford.edu> wrote: >>> >>>>> > Is there any hidden connection between the insistence of these LEDs on >>>>> > continuing to emit light long after they've been turned off, and the >>>>> > insistence of the participants in this thread in continuing to re-emit >>>>> > screenfuls and screenfuls of previous posts, before finally adding a >>>>> > one-sentence comment at the end?!?!?! >>>> >>>> >>>>> Modern newsreaders often run on machines with LED backlights? ;) >>>>> Cheers, Phil Hobbs >>>> >>>>This thread really has been off the charts in the unwillingness of >>>>posters to trim out unnecessary cruft when they reply! >>> >>>Get some scroll bars. They're not expensive. >>> >> >>Even easier if you're using Agent and perhaps other newsreaders. Use your >>scroll wheel. One click will page down. > > The only thing worse[Slappity slap]Shaddup already, Dimmy.
Reply by ●April 13, 20112011-04-13
On Apr 12, 9:52=A0pm, wil...@nospam.pobox.com (Will Janoschka) wrote:> On Tue, 12 Apr 2011 22:34:24, George Herold <gher...@teachspin.com> > wrote: > > > > > > > On Apr 12, 2:45=FFpm, wil...@nospam.pobox.com (Will Janoschka) wrote: > > > On Tue, 12 Apr 2011 16:21:14, George Herold <gher...@teachspin.com> > > > wrote: > > > > > On Apr 12, 10:19 am, John Larkin > > > > <jjlar...@highNOTlandTHIStechnologyPART.com> wrote: > > > > > On Tue, 12 Apr 2011 06:50:16 -0700 (PDT), George Herold > > > > > <Big snip> > > > > > > >Thanks John, If it's due to more current because of a drop in fo=rward> > > > > >voltage, then I should see that in the current. (Which I don't..=.> > > > > >sigh) > > > > > > What's the LED driver circuit like? > > > > > I've used a few different configurations... all give the same resul=t.> > > > Coax from the signal generator, daisy chains to the 'scope and on t=o> > > > the the LED. =FFThere I had 50 ohms to ground and in parallel 500 o=hms> > > > feeding the LED to ground. =FFOriginally there was a few inches of =wire> > > > between the 500 ohm resistor and the LED, but I later tightened it =up> > > > and put everything right at the LED. =FFI later just feed the LED > > > > through a 50 ohm resistor. > > > > > The PD circuit is standard TIA > > > > >http://img651.imageshack.us/i/tia2.png/ > > > > > I'm going to write to OSI (the PD maker.) =FFI wanted to be sure I > > > > wasn't doing something stupid beofre contacting them... > > > > > George H. > > > > > > >OK let me try a totally different idea. Can the stray capacitanc=e of> > > > > >'stuff' have a long tail like that. Charges moving around on pie=ces> > > > > >of plastic/fiber glass or something? > > > > > > Probably not the tail you're seeing. PCB 'capacitors' can have 'h=ook'> > > > > behavior, but your waveforms don't look like that. > > > > > > Post (or email me) your LED driver and pd circuits, and I'll see =if I> > > > > can spot anything. > > > > > > >I could air wire the circuit and see what that does... > > > > > > Time constants in the microseconds probably aren't strays. > > > > > > John- Hide quoted text - > > > > > > - Show quoted text - > > > > Do you have any kind of a chopper or shutter that you could > > > use to isolate =FFthe time constant(s) of the PD frome those of the > > > LED/ laser?- Hide quoted text - > > > > - Show quoted text - > > > Yeah, I was thinking about sweeping a laser across the PD face, with a > > rotating mirror or something. =A0But then it's real optics and not just > > sticking an LED against a PD. > > > George H. > > =A0What is it that you want to measure? =A0Please note 'that that' > =A0measurement =A0will have nothing to do with other photodiodes!- Hide q=uoted text -> > - Show quoted text -Hmm, Well it would give me a nice light pulse. I could control the width of the pulse by the rotation speed and distance. Optical choppers, or shutters are going to be much slower. At least the ones I know of. George H.
Reply by ●April 13, 20112011-04-13
On Wed, 13 Apr 2011 07:26:58 +0100, John Devereux <john@devereux.me.uk> wrote:>Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> writes: > >> On Tue, 12 Apr 2011 21:17:38 +0100, John Devereux >> <john@devereux.me.uk> wrote: >> >>>George Herold <gherold@teachspin.com> writes: >>> >>>> On Apr 12, 11:12�am, John Devereux <j...@devereux.me.uk> wrote: >>>>> George Herold <gher...@teachspin.com> writes: >>>>> > I� looking at the step response of a photodiode (PD). �I�m stepping >>>>> > the current into a LED such that the step doubles the photo current >>>>> > from the PD. �(I�m not starting with the LED off, but on slightly.) >>>>> > Here�s a �scope shot. �The bottom trace in the PD response. �(The top >>>>> > is the voltage step to the LED (through 100 ohms)... AC coupled to get >>>>> > rid of a big DC offset.) >>>>> >>>>> >http://img189.imageshack.us/i/tek0024.png/ >>>>> >>>>> > There is this long tail on the step response. �Here�s the same picture >>>>> > with the timebase slowed down. >>>>> >>>>> >http://img812.imageshack.us/i/tek0025.png/ >>>>> >>>>> > Looks something like a 2-2.5 us tail on the step. >>> >>>[...] >>> >>>>> >>>>> >http://img52.imageshack.us/i/tek0026.png/ >>>>> > The red LED is the trace that is a bit higher. �I�m looking to see if >>>>> > I can dig up any blue or white LED�s. >>>>> >>>>> > Any other ideas how I might determine if that's what I'm seeing... >>>>> >>>>> > Oh, the PD is a OSI-optoelectroncs PIN-3CD (3.2mm^2 area) reversed >>>>> > biased at ~12V. >>>>> >>>>> Hi George, >>>>> >>>>> You may find VCSELs easier to use than laster diodes. They can usually >>>>> be safely driven at constant current and have ~circular beams, some of >>>>> them have built-in collimator lenses too, They are noisy compared to >>>>> LEDs if that is an issue, but are designed to be modulated very quickly >>>>> (GHz), >>>> >>>> Thanks John, I've got lotsa laser diodes. VCSELs sound expensive. >>>> Who sells them? >>> >>>They're quite affordable, comparable to laser diodes really depending on >>>type of course. >>> >>>I bought some from Roithner <http://www.roithner-laser.com/> (European >>>company, they have a huge range of laser diodes and leds). Looks like >>>cheapest is $9.25 for PM85-D1POU (2mW 850nm with dome lens, 2 degree >>>beam). >> >> Nice. Any hassles with end-use certificates or do they just ship >> whatever you order asap? > >Not sure what you mean but never had any hassle with anything like >that.I had an order for some photodiodes held up for a week and a half because I made the mistake of dealing with the US office of a European company.>Then again I never tried to buy the $42000 15kW laser diode >either.We do have the clearances and documentation necessary to deal with stuff that's actually a real threat (ie. on the munitions list), but it sucks to have to hand over proprietary commercial information to foreigners for no good reason.>I'd probably blow it up :)If it blows up by itself it might actually be something worth tracking.>Shipping is normally a few days (from them in Austria to me in the >UK). They do seem to stock the things I have bought. Shipping and other >charges can be a bit expensive for "hobbyist" uses IME.Sounds good to me.
