Blue LED at 3.3V
in [Design]
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From: Spehro Pefhany on 27 May 2010 07:21 On Thu, 27 May 2010 00:48:36 -0400, the renowned Bitrex <bitrex(a)de.lete.earthlink.net> wrote: > >Using the specs from the 74HC14, in this circuit it oscillates at about >140Khz with a 1 meg resistor: Well, you'd expect something of the order of 2*R*C where C is something like five puffs, so 100kHz-ish, rough order of magnitude. Best regards, Spehro Pefhany -- "it's the network..." "The Journey is the reward" speff(a)interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
From: John Devereux on 27 May 2010 11:01 Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> writes: > On Wed, 26 May 2010 15:59:34 -0700, John Larkin > <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Thu, 27 May 2010 08:51:22 +1000, Grant <omg(a)grrr.id.au> wrote: >> >>>On Wed, 26 May 2010 15:29:21 -0700, Jim Thompson <To-Email-Use-The-Envelope-Icon(a)On-My-Web-Site.com> wrote: >>> >>>>On Wed, 26 May 2010 15:10:15 -0700, John Larkin >>>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>>> >>>>>On Wed, 26 May 2010 07:31:33 -0700 (PDT), George Herold >>>>><gherold(a)teachspin.com> wrote: >>>>> [...] >>>>>> >>>>>> >>>>>> >>>>>>+3.3V----+-----------+ >>>>>> | | >>>>>> |\| V This is diode or R >>>>>> | \ - >>>>>> +--+| >--+-CC---+ >>>>>> | | / | | >>>>>> | |/| | V light comes out here >>>>>> +------RR--+ - >>>>>> | >>>>>> GND >>>>>> >>>>>>The IC is a schmitt trigger. (And connected to ground also... >>>>>>connection not shown) >>>>>> >>>>>>George H. >>>>>> >>>>>> >>>>> >>>>>The schmitt has to be an inverter to oscillate, of course. I left out >>>>>the bubble. >>>>> >>>>>RR could be a short, then it would oscillate faster! >>>>> >>>>>John >>>> >>>>Excuses! Excuses! Excuses! Where does a capacitor belong? >>> >>>Stray? >> >>Sure. CMOS ICs have input capacitance. I guess JT doesn't know much >>about CMOS ICs. >> >>I obviously left out the cap, on purpose, to hit the "one resistor" >>target. It *will* oscillate without a discrete cap. What else could it >>possibly do? >> >>John >> > > At a ridiculous speed, IF at all.... giving him the doubt that he > "left off the bubble"... what a dork fish :-) I didn't notice - it was pretty obvious to me what the idea was. It's a sketch of an idea, not a schematic entered into a cad system. I thought it was very nice, impressively minimalistic. I like the idea of using the input capacitance as a component. And as others have pointed out it in fact it runs at perfectly reasonable frequencies (lower than I would have guessed without calculating it). [...] -- John Devereux
From: Jim Thompson on 27 May 2010 13:42 On Thu, 27 May 2010 12:22:29 -0500, John Fields <jfields(a)austininstruments.com> wrote: >On Thu, 27 May 2010 08:22:46 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Thu, 27 May 2010 06:02:29 -0500, John Fields >><jfields(a)austininstruments.com> wrote: >> >> >>Just to fool around with ideas and learn things. >> >> >> >>No, that was a scribble, just an idea. I did no math and it had no >>values. >> >> >>It could be useful, both for powering LEDs and for generating bias >>voltages, like a little negative voltage for a gaasfet. Or both at the >>same time. A schmitt oscillator deesn't need a capacitor just because >>you're used to seeing one. >> >>Why do ideas offend you so? >--- >Nice try, but ideas don't offend me at all; they make me a living. > >What does offend me is patronizing little shits like you. >--- > > >> >>I don't expect anything, except whining from you and JT. > >--- >It's not whining John, it's criticism. > >Of course, since you hold yourself in such high regard that critcism >of you falls on deaf ears, you must try to disguise what it really is >by demeaning it, so you call it "whining". >--- > >> >>The obvious one. > >--- >OK, then, why would it be bad idea to eliminate that resistor? >--- > >> >>Tout? Did you used to be a newspaper reporter in junior high school or >>something? > >--- >What a strange response... > >What are you trying to say? >--- > >> >>Sloman doesn't do electronics. > >--- >I wasn't talking about electronics. >--- > >>I had 5 or arguably 6 seriously good >>ideas yesterday, things that *will* be rigorously implemented and >>sold. And of course a bunch of silly ideas. If you aren't willing to >>create silly ideas, and make mistakes doing it, you're not going to >>ever come up with the seriously good ones. The rigor can come later. > >--- >Hey, that's a pretty neat trick; patting yourself on the back while >spouting platitudes! > >How typically Larkinese... >--- > [multi-snipped] An Obama wannabe ?:-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy
From: John Larkin on 27 May 2010 14:13 On Wed, 26 May 2010 22:01:00 -0400, Spehro Pefhany <speffSNIP(a)interlogDOTyou.knowwhat> wrote: >On Wed, 26 May 2010 21:36:02 -0400, the renowned Phil Hobbs ><pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> >>Might need a cap at the input, but otherwise OK, I think. If you make >>the resistor big enough, the input capacitance of the inverter should >>make it work fine. Nice low parts count. >> >>Cheers >> >>Phil Hobbs > >A typical blue LED won't actually be off with a Si diode in series and >3.3V, even without considering temperature and tolerance on the 3.3V. > >Can be fixed with two Si diodes in series the way I drew it (but even >that might be a bit marginal) or use a red LED for the diode. > This is nice: +3.3 | | led | | c +3.3-------R-------b BCX70K e | | | gnd R is 330K maybe. Current will be around 5 mA down to Vcc-Vled of maybe 0.2 volts. The BCXs are beta-binned, plenty tight enough for an LED. John
From: Jim Thompson on 27 May 2010 18:46
On Thu, 27 May 2010 11:13:56 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Wed, 26 May 2010 22:01:00 -0400, Spehro Pefhany ><speffSNIP(a)interlogDOTyou.knowwhat> wrote: > >>On Wed, 26 May 2010 21:36:02 -0400, the renowned Phil Hobbs >><pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> >>> >>>Might need a cap at the input, but otherwise OK, I think. If you make >>>the resistor big enough, the input capacitance of the inverter should >>>make it work fine. Nice low parts count. >>> >>>Cheers >>> >>>Phil Hobbs >> >>A typical blue LED won't actually be off with a Si diode in series and >>3.3V, even without considering temperature and tolerance on the 3.3V. >> >>Can be fixed with two Si diodes in series the way I drew it (but even >>that might be a bit marginal) or use a red LED for the diode. >> > >This is nice: > > +3.3 > | > | > led > | > | > c > +3.3-------R-------b BCX70K > e > | > | > | > gnd > > >R is 330K maybe. Current will be around 5 mA down to Vcc-Vled of maybe >0.2 volts. The BCXs are beta-binned, plenty tight enough for an LED. > >John > Sure is temperature stable, too... http://analog-innovations.com/SED/Larkins_Folly_LED_Driver.pdf :-P ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | The only thing bipartisan in this country is hypocrisy |