Fred Bloggs wrote:> > > John Larkin wrote: > >> >> For a more serious challenge, use the live 7-seg display itself as the >> ambient light sensor. No ADC allowed. For advanced credit, no extra >> parts allowed at all, just firmware. >> > > Is that for continuous adjustment or just Lo/Hi operation thresholding?What do we get for a solution that uses the 7 Seg display, no ADC, no extra parts, and that can give light-intensity information - maybe to give (say) 4 drive levels into the LEDs ? -jg
using a LED as a light sensor
Started by ●May 6, 2006
Reply by ●May 7, 20062006-05-07
Reply by ●May 7, 20062006-05-07
On Sun, 07 May 2006 17:04:11 GMT, the renowned Fred Bloggs <nospam@nospam.com> wrote:> > >John Larkin wrote: > >> >> For a more serious challenge, use the live 7-seg display itself as the >> ambient light sensor. No ADC allowed. For advanced credit, no extra >> parts allowed at all, just firmware. >> > >Is that for continuous adjustment or just Lo/Hi operation thresholding?Either way is possible. Perhaps not repeatable or reliable. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by ●May 7, 20062006-05-07
Spehro Pefhany wrote:> On Sun, 07 May 2006 17:04:11 GMT, the renowned Fred Bloggs > <nospam@nospam.com> wrote: > > >> >>John Larkin wrote: >> >> >>>For a more serious challenge, use the live 7-seg display itself as the >>>ambient light sensor. No ADC allowed. For advanced credit, no extra >>>parts allowed at all, just firmware. >>> >> >>Is that for continuous adjustment or just Lo/Hi operation thresholding? > > > Either way is possible. Perhaps not repeatable or reliable. > > > Best regards, > Spehro PefhanyWell I'm not getting how this is done without extra circuits and just firmware, where "extra circuits" is anything other than a LED driver, or IOW only circuits that are strictly output and no inputs. I can see how you could reverse the voltage across the whole array by opening or driving the common and then detecting reverse current, but no detection ckts are allowed.
Reply by ●May 7, 20062006-05-07
Fred Bloggs wrote:> Well I'm not getting how this is done without extra circuits and just > firmware, where "extra circuits" is anything other than a LED driver, or > IOW only circuits that are strictly output and no inputs. I can see how > you could reverse the voltage across the whole array by opening or > driving the common and then detecting reverse current, but no detection > ckts are allowed.Software can change most micro digital outputs to digital inputs. You have that and time to play with.
Reply by ●May 7, 20062006-05-07
On Sun, 07 May 2006 21:07:08 GMT, the renowned Fred Bloggs <nospam@nospam.com> wrote:> > >Spehro Pefhany wrote: >> On Sun, 07 May 2006 17:04:11 GMT, the renowned Fred Bloggs >> <nospam@nospam.com> wrote: >> >> >>> >>>John Larkin wrote: >>> >>> >>>>For a more serious challenge, use the live 7-seg display itself as the >>>>ambient light sensor. No ADC allowed. For advanced credit, no extra >>>>parts allowed at all, just firmware. >>>> >>> >>>Is that for continuous adjustment or just Lo/Hi operation thresholding? >> >> >> Either way is possible. Perhaps not repeatable or reliable. >> >> >> Best regards, >> Spehro Pefhany > >Well I'm not getting how this is done without extra circuits and just >firmware, where "extra circuits" is anything other than a LED driver, or >IOW only circuits that are strictly output and no inputs. I can see how >you could reverse the voltage across the whole array by opening or >driving the common and then detecting reverse current, but no detection >ckts are allowed.Preset the output to a known level (eg. Vss or Vdd), switch the output drive to an input and measure the time for the input, diode and stray capacitance to charge with the photodiode current from the initial level to the input threshold. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
Reply by ●May 7, 20062006-05-07
On Sun, 07 May 2006 17:46:26 -0400, Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote:>On Sun, 07 May 2006 21:07:08 GMT, the renowned Fred Bloggs ><nospam@nospam.com> wrote: > >> >> >>Spehro Pefhany wrote: >>> On Sun, 07 May 2006 17:04:11 GMT, the renowned Fred Bloggs >>> <nospam@nospam.com> wrote: >>> >>> >>>> >>>>John Larkin wrote: >>>> >>>> >>>>>For a more serious challenge, use the live 7-seg display itself as the >>>>>ambient light sensor. No ADC allowed. For advanced credit, no extra >>>>>parts allowed at all, just firmware. >>>>> >>>> >>>>Is that for continuous adjustment or just Lo/Hi operation thresholding? >>> >>> >>> Either way is possible. Perhaps not repeatable or reliable. >>> >>> >>> Best regards, >>> Spehro Pefhany >> >>Well I'm not getting how this is done without extra circuits and just >>firmware, where "extra circuits" is anything other than a LED driver, or >>IOW only circuits that are strictly output and no inputs. I can see how >>you could reverse the voltage across the whole array by opening or >>driving the common and then detecting reverse current, but no detection >>ckts are allowed. > >Preset the output to a known level (eg. Vss or Vdd), switch the output >drive to an input and measure the time for the input, diode and stray >capacitance to charge with the photodiode current from the initial >level to the input threshold. > >Yup. That could be interleaved with the digit scan. John
Reply by ●May 7, 20062006-05-07
Jonathan Kirwan wrote:> On Sun, 07 May 2006 07:11:09 -0500, John Fields > <jfields@austininstruments.com> wrote: > > >>> in the vessel(FS6 gas filled) >> >>--- >>Fluorine Hexasulfide? Must be some nasty shit... >>--- > > > I suspect it is SF6: > http://en.wikipedia.org/wiki/SF6 > > Jonyes, my mistake, just a type'o . -- Real Programmers Do things like this. http://webpages.charter.net/jamie_5
Reply by ●May 7, 20062006-05-07
CBFalconer wrote:> Jamie wrote: > > ... snip ... > >>in the vessel(FS6 gas filled) we do use a 12 level photo >>multiplier because we need to know when the slightest hint of >>photon is present in the vessel. this normally indicates that we >>mite have a vacuum problem, LEDS and even Silicone photo >>detectors are not sensitive enough for that application. (at >>least they wasn't back when it was designed). > > > We used to criminally overvoltage selected photomultipliers for > coincidence detectors, which needed to detect a single particle > hitting the crystal, after which hopefully at least one photon got > collected on the photo-cathode. We used in the order of 2kV on > tubes rated at 1 kV. You turned up the voltage, and if they didn't > start generating violent noise you kept them. The others went back > to the stockroom. I seem to remember a 1P21. >i don't recall the number but we use one that has a center tap on the filament, that way we can move the tap when a filament opens from the outside. :) we never needed to increase the voltage pass spec as far as i know. what i love is when we have an arc on the Pie transformers., makes nice burns in the litz wound pie xformer and some times strikes and arc on the Plexiglas mounting deck for the input side of the diode multiplier stack. -- Real Programmers Do things like this. http://webpages.charter.net/jamie_5
Reply by ●May 7, 20062006-05-07
In art. <flis52l97qi124ritjkt0o22q0dsd5c4b5@4ax.com>, John Larkin wrote:>On Sun, 07 May 2006 09:36:02 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@My-Web-Site.com> wrote:>>Are LED's more efficient as light sensors than so called photo diodes? > >They're pitiful, especially as pv generators, and merely real bad as >reverse-biased photodiodes. The active area's tiny, among other >things.Although I have found the small area to be a big consideration, I have also found some to be better at converting sunlight received by that area into electrical power than same area of monocrystalline solar cell. Most notably with some older tech GaP and GaAsP types as opposed to any more modern ones with optically resonant or semi-resonant structures/layers to favor efficiency in an amission band at the expense of efficiency in an absorption band. Also notably I have not found GaN or InGaN ones to be efficient as solar cells - I suspect emission band is displaced from the absorption band in many of those by the emission being a process with more than one downward jump. Also, many GaN/InGaN LEDs could have absorption bands largely attenuated by being in the UV and attenuated by building materials of the LED, let alone whether the LED chip has any resonant or semi-resonant structures (layer thicknesses) in favor of the emision band and against any absorption band! Keep in mind that GaAs and GaP have been proposed as solar cell materials! Not only have these achieved more power per unit area when illuminated with sunlight (higher voltage outweighs lower current that results from a smaller bandwidth of wavelengths being utilizeable due to longer wavelength infrared not being utilizeable), but also has been proposed solar panels with GaAs or GaP being placed over silicon solar panels, due to some of the infrared not utilizeable by GaAs or more likely GaP passing through to be utilized by a proposed underlying silicon panel! - Don Klipstein (don@misty.com)
Reply by ●May 8, 20062006-05-08
Jamie wrote:> CBFalconer wrote: > > Jamie wrote: >> >> ... snip ... >> >>> in the vessel(FS6 gas filled) we do use a 12 level photo >>> multiplier because we need to know when the slightest hint of >>> photon is present in the vessel. this normally indicates that we >>> mite have a vacuum problem, LEDS and even Silicone photo >>> detectors are not sensitive enough for that application. (at >>> least they wasn't back when it was designed). >> >> We used to criminally overvoltage selected photomultipliers for >> coincidence detectors, which needed to detect a single particle >> hitting the crystal, after which hopefully at least one photon got >> collected on the photo-cathode. We used in the order of 2kV on >> tubes rated at 1 kV. You turned up the voltage, and if they didn't >> start generating violent noise you kept them. The others went back >> to the stockroom. I seem to remember a 1P21. >> > i don't recall the number but we use one that has a center tap on the > filament, that way we can move the tap when a filament opens from the > outside. :) > we never needed to increase the voltage pass spec as far as i know. > what i love is when we have an arc on the Pie transformers., makes nice > burns in the litz wound pie xformer and some times strikes and arc on > the Plexiglas mounting deck for the input side of the diode multiplier > stack.You are trolling. Photomultipliers don't have filaments. -- "If you want to post a followup via groups.google.com, don't use the broken "Reply" link at the bottom of the article. Click on "show options" at the top of the article, then click on the "Reply" at the bottom of the article headers." - Keith Thompson More details at: <http://cfaj.freeshell.org/google/> Also see <http://www.safalra.com/special/googlegroupsreply/>
