Yep - sorry about that, R1 seems not to be there.

RP


On 14/12/2007, Justin Richards <justin.richards@gmail.com> wrote:
>
> Thanks Russell/Richard for taking the time to explain its operation.
> I assume R1 is R2.
>
> Thanks Again
>
> Justin
>
> On Dec 4, 2007 8:17 PM, Richard Prosser <rhprosser@gmail.com> wrote:
> > Justin,
> > 1. Q1 & Q2 are initially turned on, and current flows though the
> inductor L1
> > & R1
> > 2. As the current increases, the voltage across R1 increases. Once a
> > threashold voltage is reached (about 1 diode drop below the base voltage
> of
> > Q2) then Q2 starts to turn off.
> > 3. This turns Q1 off. The voltage on the collector of Q1 drops pulling
> the
> > base of Q2 lower via R6 and turning it off completely.
> > 4. Since the current through L1 can't immediately stop, the voltage at
> Q1
> > collector drops below zero volts to whatever voltage is required to turn
> the
> > diodes on. This is a straightforward flyback type effect.
> > 5. The current though L1, R1 and the diodes then decays as the energy
> stored
> > in the inductor is used until the voltage across R1 drops sufficiently
> for
> > Q2 to start tuning on again.
> > 5. This turns Q1 on, the collector voltage rises, turns Q2 on harder,
> and
> > starts the supply current flowing through L1 & R1 again.
> > 6. The process repeats.
> >
> > Now - how best to stabilise the average diode current with changing
> input
> > voltage?
> >
> > RP
> >
> >
> >
> > On 04/12/2007, Justin Richards <justin.richards@gmail.com> wrote:
> > >
> > > I too had a giggle, then my thoughts turned to Jinx having a fantastic
> > > Xmas.  Heres to a very very merry Xmas Jinx.
> > >
> > > How do I remove myself from that PICLIST map ...
> > >
> > > But back to the LED driver, I have tried to get an understanding of
> > > how these 'simple' ccts actually work.
> > >
> > > I tried to follow what would happen when the cct was powered up and I
> > > cant see how the LEDs would ever light up.
> > >
> > > Are the LEDs around the wrong way.  Can anyone do a quick walk thru of
> > > how this cct would work.  Any enlightening will be greatly
> > > appreciated.
> > >
> > > Cheers Justin
> > >
> > > On Dec 4, 2007 5:09 PM, Jinx <joecolquitt@clear.net.nz> wrote:
> > > > > Jinx Soprano?  :-)
> > > >
> > > > Hehe. I see myself more in the Joe Pesci mold -
> > > >
> > > > "What do ya mean, funny? Let me understand this cause, I don't know
> > > > maybe it's me, I'm a little ****** up maybe, but I'm funny how? I
> mean,
> > > > funny like I'm a clown, I amuse you? I make you laugh... I'm here to
> > > > *****' amuse you? What do you mean funny, funny how? How am I
> > > > funny?"
> > > >
> > > > Scary scary man
> > > >
> > > > But I shouldn't be hobnobbing on Russell's thread. Sorry R
> > > >
> > > > "This...Basil"
> > > > "This...Basil's wife"
> > > > "This...smack on head"
> > > >
> > > >
> > > > --
> > > > http://www.piclist.com PIC/SX FAQ & list archive
> > > > View/change your membership options at
> > > > http://mailman.mit.edu/mailman/listinfo/piclist
> > > >
> > > --
> > > http://www.piclist.com PIC/SX FAQ & list archive
> > > View/change your membership options at
> > > http://mailman.mit.edu/mailman/listinfo/piclist
> > >
> > --
> >
> > http://www.piclist.com PIC/SX FAQ & list archive
> > View/change your membership options at
> > http://mailman.mit.edu/mailman/listinfo/piclist
> >
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist