Blue LED at 3.3V
in [Design]
|
From: Phil Hobbs on 26 May 2010 22:40 Jim Thompson wrote: > On Wed, 26 May 2010 21:55:56 -0400, Phil Hobbs > <pcdhSpamMeSenseless(a)electrooptical.net> wrote: > >> Jim Thompson wrote: >>> On Wed, 26 May 2010 21:36:02 -0400, Phil Hobbs >>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>> >>>> Jim Thompson wrote: >>>>> On Thu, 27 May 2010 07:56:08 +1000, David Eather <eather(a)tpg.com.au> >>>>> wrote: >>>>> >>>>>> On 27/05/2010 12:31 AM, George Herold wrote: >>>>>>> On May 26, 8:00 am, David Eather<eat...(a)tpg.com.au> wrote: >>>>>>>> On 26/05/2010 4:10 AM, John Larkin wrote: >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>>> On Tue, 25 May 2010 10:22:59 -0700, Tim Wescott<t...(a)seemywebsite.now> >>>>>>>>> wrote: >>>>>>>>>> On 05/25/2010 10:18 AM, rich wrote: >>>>>>>>>>> I need to drive a blue led from 3.3V. Most of the SMD blue leds I >>>>>>>>>>> find have a Vf equal to or greater than 3.3V. >>>>>>>>>>> I am curious how others are dealing with this. >>>>>>>>>> That pretty much demands a voltage boost of some sort. Depending on how >>>>>>>>>> many lights you have, how much power you're willing to waste, how much >>>>>>>>>> design time you want to spend and how expensive you want the final >>>>>>>>>> product to be, your choices sort of boil down to a switcher with >>>>>>>>>> inductors and diodes and all that, or a current pump. >>>>>>>>>> Most of us would solve this problem by looking for a suitable IC. >>>>>>>>>> _Some_ of us would do it with two transistors, an inductor, and a cap, >>>>>>>>>> then brag about only needing one $.001 resistor instead of three. >>>>>>>>> One resistor: >>>>>>>>> ftp://jjlarkin.lmi.net/LED_boost.JPG >>>>>>>>> John >>>>>>>> Hi, >>>>>>>> >>>>>>>> Could you post his circuit onwww.filedropper.comorwww.filefactory.com >>>>>>>> or something similar - I just can connect.- Hide quoted text - >>>>>>>> >>>>>>>> - Show quoted text - >>>>>>> +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. >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>> Thanks. >>>>> Theory of "operation" is left as an exercise for the student :-) >>>>> >>>>> ...Jim Thompson >>>> 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 >>> I think you'd need to tailor the rate to accommodate the source/sink >>> capability of the inverter (not shown, bubble to be imagined :-) >>> >>> ...Jim Thompson >> Urinating contests aren't my cup of tea. ;) >> >> Cheers >> >> Phil Hobbs > > But John "I left out the bubble" Larkin makes it so-o-o-o easy ;-) > > I think he's the one going senile. He claims it's me, but I feel (and > think) like an 18 year old :-) > > ...Jim Thompson Feeling that way is the first symptom. ;) Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
From: Jim Thompson on 26 May 2010 23:27 On Wed, 26 May 2010 22:40:50 -0400, Phil Hobbs <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >Jim Thompson wrote: >> On Wed, 26 May 2010 21:55:56 -0400, Phil Hobbs >> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >> >>> Jim Thompson wrote: >>>> On Wed, 26 May 2010 21:36:02 -0400, Phil Hobbs >>>> <pcdhSpamMeSenseless(a)electrooptical.net> wrote: >>>> >>>>> Jim Thompson wrote: >>>>>> On Thu, 27 May 2010 07:56:08 +1000, David Eather <eather(a)tpg.com.au> >>>>>> wrote: >>>>>> >>>>>>> On 27/05/2010 12:31 AM, George Herold wrote: >>>>>>>> On May 26, 8:00 am, David Eather<eat...(a)tpg.com.au> wrote: >>>>>>>>> On 26/05/2010 4:10 AM, John Larkin wrote: >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>>> On Tue, 25 May 2010 10:22:59 -0700, Tim Wescott<t...(a)seemywebsite.now> >>>>>>>>>> wrote: >>>>>>>>>>> On 05/25/2010 10:18 AM, rich wrote: >>>>>>>>>>>> I need to drive a blue led from 3.3V. Most of the SMD blue leds I >>>>>>>>>>>> find have a Vf equal to or greater than 3.3V. >>>>>>>>>>>> I am curious how others are dealing with this. >>>>>>>>>>> That pretty much demands a voltage boost of some sort. Depending on how >>>>>>>>>>> many lights you have, how much power you're willing to waste, how much >>>>>>>>>>> design time you want to spend and how expensive you want the final >>>>>>>>>>> product to be, your choices sort of boil down to a switcher with >>>>>>>>>>> inductors and diodes and all that, or a current pump. >>>>>>>>>>> Most of us would solve this problem by looking for a suitable IC. >>>>>>>>>>> _Some_ of us would do it with two transistors, an inductor, and a cap, >>>>>>>>>>> then brag about only needing one $.001 resistor instead of three. >>>>>>>>>> One resistor: >>>>>>>>>> ftp://jjlarkin.lmi.net/LED_boost.JPG >>>>>>>>>> John >>>>>>>>> Hi, >>>>>>>>> >>>>>>>>> Could you post his circuit onwww.filedropper.comorwww.filefactory.com >>>>>>>>> or something similar - I just can connect.- Hide quoted text - >>>>>>>>> >>>>>>>>> - Show quoted text - >>>>>>>> +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. >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> Thanks. >>>>>> Theory of "operation" is left as an exercise for the student :-) >>>>>> >>>>>> ...Jim Thompson >>>>> 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 >>>> I think you'd need to tailor the rate to accommodate the source/sink >>>> capability of the inverter (not shown, bubble to be imagined :-) >>>> >>>> ...Jim Thompson >>> Urinating contests aren't my cup of tea. ;) >>> >>> Cheers >>> >>> Phil Hobbs >> >> But John "I left out the bubble" Larkin makes it so-o-o-o easy ;-) >> >> I think he's the one going senile. He claims it's me, but I feel (and >> think) like an 18 year old :-) >> >> ...Jim Thompson > >Feeling that way is the first symptom. ;) > >Cheers > >Phil Hobbs Nah! I thinks like an 18 year-old, then I falls asleep ;-) ...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: Don Klipstein on 27 May 2010 00:00 In article <0rlrv5tahbrkoqk9vt3dods63p8i5s6lt2(a)4ax.com>, Jim Thompson wrote: >On Wed, 26 May 2010 21:55:56 -0400, Phil Hobbs ><pcdhSpamMeSenseless(a)electrooptical.net> wrote: <I snip to this point to edit for space> >>Urinating contests aren't my cup of tea. ;) <I snip a bit more to edit for space, with hope of maintaining attribution> >But John "I left out the bubble" Larkin makes it so-o-o-o easy ;-) > >I think he's the one going senile. He claims it's me, but I feel (and >think) like an 18 year old :-) How about when I feel like an 18-year-old? When I do, there are usually none willing around! (Besides, I have exchanged vows with someone that I love, and I have fulfilled them for over 20 years without exception of so much as a second, and my main barrier to being married to him is marriage law where I live... unlike a fair portion of New England, along with all of Canada, Belgium, Spain, South Africa and Holland [IIRC].) -- - Don Klipstein (don(a)misty.com)
From: Bitrex on 27 May 2010 00:48 John Larkin 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: >>>> >>>>> On May 26, 8:00 am, David Eather <eat...(a)tpg.com.au> wrote: >>>>>> On 26/05/2010 4:10 AM, John Larkin wrote: >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> >>>>>>> On Tue, 25 May 2010 10:22:59 -0700, Tim Wescott<t...(a)seemywebsite.now> >>>>>>> wrote: >>>>>>>> On 05/25/2010 10:18 AM, rich wrote: >>>>>>>>> I need to drive a blue led from 3.3V. Most of the SMD blue leds I >>>>>>>>> find have a Vf equal to or greater than 3.3V. >>>>>>>>> I am curious how others are dealing with this. >>>>>>>> That pretty much demands a voltage boost of some sort. Depending on how >>>>>>>> many lights you have, how much power you're willing to waste, how much >>>>>>>> design time you want to spend and how expensive you want the final >>>>>>>> product to be, your choices sort of boil down to a switcher with >>>>>>>> inductors and diodes and all that, or a current pump. >>>>>>>> Most of us would solve this problem by looking for a suitable IC. >>>>>>>> _Some_ of us would do it with two transistors, an inductor, and a cap, >>>>>>>> then brag about only needing one $.001 resistor instead of three. >>>>>>> One resistor: >>>>>>> ftp://jjlarkin.lmi.net/LED_boost.JPG >>>>>>> John >>>>>> Hi, >>>>>> >>>>>> Could you post his circuit onwww.filedropper.comorwww.filefactory.com >>>>>> or something similar - I just can connect.- Hide quoted text - >>>>>> >>>>>> - Show quoted text - >>>>> >>>>> >>>>> +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 > > Using the specs from the 74HC14, in this circuit it oscillates at about 140Khz with a 1 meg resistor: Version 4 SHEET 1 880 680 WIRE 128 192 112 192 WIRE 224 192 192 192 WIRE 112 256 112 192 WIRE 224 256 224 192 WIRE 224 256 192 256 FLAG 144 96 0 FLAG 144 16 Vcc FLAG 288 336 0 FLAG 288 112 Vcc FLAG 112 320 0 SYMBOL Digital\\schmtinv 128 128 R0 SYMATTR InstName A1 SYMATTR SpiceLine Td = 5n SYMATTR Value2 Vhigh=3.3 Vt=0.85 Vh=0.56 SYMBOL voltage 144 0 R0 WINDOW 123 0 0 Left 0 WINDOW 39 0 0 Left 0 SYMATTR InstName V1 SYMATTR Value 3.3 SYMBOL res 208 240 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R1 SYMATTR Value 1MEG SYMBOL cap 288 176 R90 WINDOW 0 0 32 VBottom 0 WINDOW 3 27 62 VTop 0 SYMATTR InstName C1 SYMATTR Value 10n SYMBOL res 272 176 R0 SYMATTR InstName R3 SYMATTR Value 220 SYMBOL LED 272 272 R0 SYMATTR InstName D1 SYMATTR Value NSCW100 SYMATTR Description Diode SYMATTR Type diode SYMBOL res 272 96 R0 SYMATTR InstName R2 SYMATTR Value 1k SYMBOL cap 96 256 R0 SYMATTR InstName C2 SYMATTR Value 3.5p TEXT -6 54 Left 0 !.tran 0.1
From: John Larkin on 27 May 2010 01:07
On Thu, 27 May 2010 00:48:36 -0400, Bitrex <bitrex(a)de.lete.earthlink.net> wrote: >John Larkin 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: >>>>> >>>>>> On May 26, 8:00 am, David Eather <eat...(a)tpg.com.au> wrote: >>>>>>> On 26/05/2010 4:10 AM, John Larkin wrote: >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>>> On Tue, 25 May 2010 10:22:59 -0700, Tim Wescott<t...(a)seemywebsite.now> >>>>>>>> wrote: >>>>>>>>> On 05/25/2010 10:18 AM, rich wrote: >>>>>>>>>> I need to drive a blue led from 3.3V. Most of the SMD blue leds I >>>>>>>>>> find have a Vf equal to or greater than 3.3V. >>>>>>>>>> I am curious how others are dealing with this. >>>>>>>>> That pretty much demands a voltage boost of some sort. Depending on how >>>>>>>>> many lights you have, how much power you're willing to waste, how much >>>>>>>>> design time you want to spend and how expensive you want the final >>>>>>>>> product to be, your choices sort of boil down to a switcher with >>>>>>>>> inductors and diodes and all that, or a current pump. >>>>>>>>> Most of us would solve this problem by looking for a suitable IC. >>>>>>>>> _Some_ of us would do it with two transistors, an inductor, and a cap, >>>>>>>>> then brag about only needing one $.001 resistor instead of three. >>>>>>>> One resistor: >>>>>>>> ftp://jjlarkin.lmi.net/LED_boost.JPG >>>>>>>> John >>>>>>> Hi, >>>>>>> >>>>>>> Could you post his circuit onwww.filedropper.comorwww.filefactory.com >>>>>>> or something similar - I just can connect.- Hide quoted text - >>>>>>> >>>>>>> - Show quoted text - >>>>>> >>>>>> >>>>>> +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 >> >> > >Using the specs from the 74HC14, in this circuit it oscillates at about >140Khz with a 1 meg resistor: > Yup, it's perfectly reasonable. 5 pF, 1M, tau is 5 usec. Right in the ballpark. What else could it possibly do than oscillate? John |