Reply by Ted September 19, 20062006-09-19
On 8 May 2006 04:22:25 -0700, "Antti" <Antti.Lukats@xilant.com> wrote:

>well I was able to make a iopad oscillator that had frequency change >10% based on light intensity, and even that was possible bad solution, >eg the change could be even larger. > >but getting stable absolute reading is probably more difficult or >impossible due to temperature, effects, etc > >Antti
LEDs are decent candidates for RF VFOs (variable frequency oscillators) in place of specialized varaiable capacitance diodes. What we've found is that the LED-based VFO must be kept in a light-shielded enclosure due to the effect described. Not usually a problem, since the VFO should be in an RF-shielded enclosure anyway.
Reply by Deep Reset June 16, 20062006-06-16
"BrunoG" <noreply@micro-examples.com> wrote in message 
news:4492c725$0$991$ba4acef3@news.orange.fr...
> "Rufus V. Smith" <nospam@nospam.com> a &#4294967295;crit dans le message de news: > 44903395$0$28047$88260bb3@news-taz.teranews.com... >> >> "BrunoG" <please_reply_in_the_forums@www.micro-examples.com> wrote in >> message news:445d31a5$0$19698$8fcfb975@news.wanadoo.fr... >>> Hi, >>> >>> Here is an idea about using a LED as a light sensor, to dim a 7-segments >>> LED display : >>> >>> http://www.micro-examples.com/public/microex-navig/doc/096-led-light-sensor.html >>> >>> Questions & comments are welcome ! >>> >>> Thanks, >>> >>> Bruno >> >> Very cool. >> >> Unfortunate about the color of the casing filtering incoming light. >> >> Could this detect the signal coming from an IR remote (well enough to >> decode), I wonder? >> >> Rufus >> >> > > Hi, thanks ! > > It's worth a try, but I don't think so, because the response time of the > diode & PIC DAC would be too long. > > Bruno > http://www.micro-examples.com/public/microex-navig/doc/096-led-light-sensor.html
OK, not quite 40kHz territory, but this looks fairly quick: http://mrl.nyu.edu/~jhan/ledtouch/index.html from here: http://www.hackaday.com/entry/1234000873073550/ Deep.
>
Reply by BrunoG June 16, 20062006-06-16
"Rufus V. Smith" <nospam@nospam.com> a &#4294967295;crit dans le message de news: 
44903395$0$28047$88260bb3@news-taz.teranews.com...
> > "BrunoG" <please_reply_in_the_forums@www.micro-examples.com> wrote in > message news:445d31a5$0$19698$8fcfb975@news.wanadoo.fr... >> Hi, >> >> Here is an idea about using a LED as a light sensor, to dim a 7-segments >> LED display : >> >> http://www.micro-examples.com/public/microex-navig/doc/096-led-light-sensor.html >> >> Questions & comments are welcome ! >> >> Thanks, >> >> Bruno > > Very cool. > > Unfortunate about the color of the casing filtering incoming light. > > Could this detect the signal coming from an IR remote (well enough to > decode), I wonder? > > Rufus > >
Hi, thanks ! It's worth a try, but I don't think so, because the response time of the diode & PIC DAC would be too long. Bruno http://www.micro-examples.com/public/microex-navig/doc/096-led-light-sensor.html
Reply by Rufus V. Smith June 14, 20062006-06-14
"BrunoG" <please_reply_in_the_forums@www.micro-examples.com> wrote in 
message news:445d31a5$0$19698$8fcfb975@news.wanadoo.fr...
> Hi, > > Here is an idea about using a LED as a light sensor, to dim a 7-segments > LED display : > > http://www.micro-examples.com/public/microex-navig/doc/096-led-light-sensor.html > > Questions & comments are welcome ! > > Thanks, > > Bruno
Very cool. Unfortunate about the color of the casing filtering incoming light. Could this detect the signal coming from an IR remote (well enough to decode), I wonder? Rufus
Reply by May 24, 20062006-05-24
dagmargoodboat@yahoo.com wrote:

 <snip>

> New measurements: > orange, 10mm, clear 3.12uA > red, 5mm, ultrabright, 20deg (est.) beam. 2.01uA > red, 5mm, ultrabright, 20deg (est.) beam. 4.14uA
Ooops -- both red LEDs above ^^^ were clear-cased. James Arthur
Reply by May 24, 20062006-05-24
John Devereux wrote:
> szekeres@pitt.edu (GregS) writes: > > > ome random, > >>junk-box devices, 1.5m from a 50w halogen > >>flood lamp: > >> > >>LEDs > >> green, bright 3mm, Hosfelt 25-302 <0.02uA > >> IRLED, unknown vintage (90's?) 4.3uA > >> old red LED 0.10uA > >> IRLED, 1970's 0.11uA > >> IRLED, Optek OP232W (TO-18) 0.2uA > >> red, ultrabright, 5mm, narrow beam 4.3uA > >> IRLED, 1997, super bright 3.4uA > >> > >> yellow, 5mm, ultrabright, Hosfelt 25-335 0.88uA > >> green, 5mm, ultrabright, Hosfelt 25-366 0.72uA > >> yellow, 10mm, low efficiency 0.08uA > >> green, 3mm, bright 0.08-0.11uA > >> red, 10mm, ultrabright 2.2uA > >> green, 5mm 0.17uA > >> red, 2mm, Dialco 555-2003 0.13uA > >> red, ultrabright, 5mm 3.6uA > >> > >> > >>PIN photodiodes > >> PN323BPA (Panasonic?) 26uA > >> TIL413 57uA > >> > >>large area photodiode, ~2.5x2.5mm 12.8uA > >> > > > > Confirms about what I measured in my junkbox. Led's are > > poor light receptors. > > True, but not impossibly so it would seem. I was actually quite > impressed by those numbers from the "ultrabright" offerings above. Of > course these are the ones with a lens that will focus the incoming > light from a much larger area than that of the led chip.
Yes, one would think a larger lens, e.g. a 10mm LED, would gather 4x as much light as a 5mm unit. Lower output from 10mm LEDs, then, indicates a less efficient photogenerating LED die. Another explanation might be variations in focus, but virtually all of the 10mm units are *very* tightly focused, e.g. <= 10 deg., excluding that theory. Apparently some dice are simply better than others. Cheers, James Arthur
Reply by May 24, 20062006-05-24
John Popelish wrote:
> dagmargoodboat@yahoo.com wrote: > > > I finally dug out (and through) my notebooks for this data from 2001: > > > > 3/14/2001 > > Short-circuit photocurrent of some random, > > junk-box devices, 1.5m from a 50w halogen > > flood lamp: > > > > LEDs > > green, bright 3mm, Hosfelt 25-302 <0.02uA > > IRLED, unknown vintage (90's?) 4.3uA > > old red LED 0.10uA > > IRLED, 1970's 0.11uA > > IRLED, Optek OP232W (TO-18) 0.2uA > > red, ultrabright, 5mm, narrow beam 4.3uA > > IRLED, 1997, super bright 3.4uA > > > > yellow, 5mm, ultrabright, Hosfelt 25-335 0.88uA > > green, 5mm, ultrabright, Hosfelt 25-366 0.72uA > > yellow, 10mm, low efficiency 0.08uA > > green, 3mm, bright 0.08-0.11uA > > red, 10mm, ultrabright 2.2uA > > green, 5mm 0.17uA > > red, 2mm, Dialco 555-2003 0.13uA > > red, ultrabright, 5mm 3.6uA > > > > > > PIN photodiodes > > PN323BPA (Panasonic?) 26uA > > TIL413 57uA > > > > large area photodiode, ~2.5x2.5mm 12.8uA > > Would you please add whether the epoxy on the various LEDs was clear, > frosted or dyed a color?
Sure. Please note that these were *crude* measurements taken five years ago, just to see the range of outputs that might be expected from good & bad photogenerating LEDs. I wasn't trying for ultimate rigor. The 1.5m lamp spacing, for example, is an estimate. The X-Y-Z location of the device tested in the (uneven) illumination field is critical, and the angles even more so. I chose the combination producing max. photocurrent in each case. That said, ... First, let's measure the spacing to the lamp: 1.54m, so 1.5m was not a bad guess. Next, check our calibration with an identifiable type measured 5 years ago: red, 2mm, diffused, Dialco 555-2003 (unit #1) 0.13uA red, 2mm, diffused, Dialco 555-2003 (unit #2) 0.11uA Okay, so we're in the ballpark. Now that I'm calibrated, I can use my recollection for device-identification wherever possible, and have the old data for sanity-checking / confirmation of ID... Here's an updated table, with as much info on each LED as I can ascertain, plus a few new entries... '------------------------------------------- Short-circuit photocurrent of some random, junk-box devices, 1.54m from a 590l, 50w halogen lamp: LEDs green, 3mm, clear light green tint, bright <0.02uA (Hosfelt 25-302) IRLED, 5mm, unknown vintage (90's?) 4.3uA old 5mm diffused red LED, 1970s 0.10uA IRLED, circa 1970s 0.11uA IRLED, Optek OP232W, clear (TO-18) 0.2uA red, ultrabright, 5mm, clear, narrow beam 4.3uA IRLED, 1997, super bright 3.4uA yellow, 5mm, ultrabright, clear, Hosfelt 25-335 0.88uA (Toshiba TLYH180P 590nm 8cd, 8deg beam) green, 5mm, ultrabright, clear, Hosfelt 25-366 0.72uA yellow, 10mm, low efficiency, diffused 0.08uA green, 3mm, bright 0.08-0.11uA red, 10mm, ultrabright 2.2uA green, 5mm 0.17uA red, 2mm, diffused, Dialco 555-2003 0.13uA red, ultrabright, 5mm 3.6uA PIN photodiodes PN323BPA (Panasonic?) 26uA TIL413 57uA large area photodiode, clear, ~2.5x2.5mm 12.8uA '------------------------------------------- New measurements: orange, 10mm, clear 3.12uA red, 5mm ultrabright, 20deg (est.) beam. 2.01uA red, 5mm ultrabright, 20deg (est.) beam. 4.14uA IR, 5mm, clear, est. 10 deg. beam 7.85uA red, 2mm, diffused, Dialco 555-2003 0.13uA red, 2mm, diffused, Dialco 555-2003 0.11uA yellow, 5mm, clear, Infineon LY-5436 0.17uA (700mcd, 591nm, 20deg.) Cheers, James Arthur
Reply by John Popelish May 24, 20062006-05-24
dagmargoodboat@yahoo.com wrote:

> I finally dug out (and through) my notebooks for this data from 2001: > > 3/14/2001 > Short-circuit photocurrent of some random, > junk-box devices, 1.5m from a 50w halogen > flood lamp: > > LEDs > green, bright 3mm, Hosfelt 25-302 <0.02uA > IRLED, unknown vintage (90's?) 4.3uA > old red LED 0.10uA > IRLED, 1970's 0.11uA > IRLED, Optek OP232W (TO-18) 0.2uA > red, ultrabright, 5mm, narrow beam 4.3uA > IRLED, 1997, super bright 3.4uA > > yellow, 5mm, ultrabright, Hosfelt 25-335 0.88uA > green, 5mm, ultrabright, Hosfelt 25-366 0.72uA > yellow, 10mm, low efficiency 0.08uA > green, 3mm, bright 0.08-0.11uA > red, 10mm, ultrabright 2.2uA > green, 5mm 0.17uA > red, 2mm, Dialco 555-2003 0.13uA > red, ultrabright, 5mm 3.6uA > > > PIN photodiodes > PN323BPA (Panasonic?) 26uA > TIL413 57uA > > large area photodiode, ~2.5x2.5mm 12.8uA
Would you please add whether the epoxy on the various LEDs was clear, frosted or dyed a color?
Reply by GregS May 24, 20062006-05-24
In article <87mzd7jscb.fsf@cordelia.devereux.me.uk>, John Devereux <jdREMOVE@THISdevereux.me.uk> wrote:
>szekeres@pitt.edu (GregS) writes: > >> ome random, >>>junk-box devices, 1.5m from a 50w halogen >>>flood lamp: >>> >>>LEDs >>> green, bright 3mm, Hosfelt 25-302 <0.02uA >>> IRLED, unknown vintage (90's?) 4.3uA >>> old red LED 0.10uA >>> IRLED, 1970's 0.11uA >>> IRLED, Optek OP232W (TO-18) 0.2uA >>> red, ultrabright, 5mm, narrow beam 4.3uA >>> IRLED, 1997, super bright 3.4uA >>> >>> yellow, 5mm, ultrabright, Hosfelt 25-335 0.88uA >>> green, 5mm, ultrabright, Hosfelt 25-366 0.72uA >>> yellow, 10mm, low efficiency 0.08uA >>> green, 3mm, bright 0.08-0.11uA >>> red, 10mm, ultrabright 2.2uA >>> green, 5mm 0.17uA >>> red, 2mm, Dialco 555-2003 0.13uA >>> red, ultrabright, 5mm 3.6uA >>> >>> >>>PIN photodiodes >>> PN323BPA (Panasonic?) 26uA >>> TIL413 57uA >>> >>>large area photodiode, ~2.5x2.5mm 12.8uA >>> >> >> Confirms about what I measured in my junkbox. Led's are >> poor light receptors. > >True, but not impossibly so it would seem. I was actually quite >impressed by those numbers from the "ultrabright" offerings above. Of >course these are the ones with a lens that will focus the incoming >light from a much larger area than that of the led chip.
I didn't measure current, but I was working with a Phillips Lumiled, and needed to get closer to the emitter. We started milling down the top piece, plastic but not really a beam forming lens. Something funny looked in the center. As the center region was cleared, I discovered the flexible inner Sylgard like material under the plastic. It was interesting and screws me up. greg
Reply by John Devereux May 24, 20062006-05-24
szekeres@pitt.edu (GregS) writes:

> ome random, >>junk-box devices, 1.5m from a 50w halogen >>flood lamp: >> >>LEDs >> green, bright 3mm, Hosfelt 25-302 <0.02uA >> IRLED, unknown vintage (90's?) 4.3uA >> old red LED 0.10uA >> IRLED, 1970's 0.11uA >> IRLED, Optek OP232W (TO-18) 0.2uA >> red, ultrabright, 5mm, narrow beam 4.3uA >> IRLED, 1997, super bright 3.4uA >> >> yellow, 5mm, ultrabright, Hosfelt 25-335 0.88uA >> green, 5mm, ultrabright, Hosfelt 25-366 0.72uA >> yellow, 10mm, low efficiency 0.08uA >> green, 3mm, bright 0.08-0.11uA >> red, 10mm, ultrabright 2.2uA >> green, 5mm 0.17uA >> red, 2mm, Dialco 555-2003 0.13uA >> red, ultrabright, 5mm 3.6uA >> >> >>PIN photodiodes >> PN323BPA (Panasonic?) 26uA >> TIL413 57uA >> >>large area photodiode, ~2.5x2.5mm 12.8uA >> > > Confirms about what I measured in my junkbox. Led's are > poor light receptors.
True, but not impossibly so it would seem. I was actually quite impressed by those numbers from the "ultrabright" offerings above. Of course these are the ones with a lens that will focus the incoming light from a much larger area than that of the led chip. -- John Devereux