On Sun, Jan 23, 2011 at 11:40 PM, RussellMc <apptechnz@gmail.com> wrote:
> That bends the brain just the wee-est amount until a few clever points
> are noted.
> Plus it is a flasher only with the LED flashing bright, then tailing off.
> You may need a second Q to get it back to a DC or flash mode as mine
> was. Maybe not.
>
> C! charges via path D3 R1 D1 C1 D2 - so starts bright and tails off.
> Pulse on Q1 base turns Q1 on, clamps C1 top to gnd so C1 bottom goes to =
=A0-Vin
>
> Q2e is drive to -Vin so Q2_b is at ground so Vbe is applied to Q2 to turn=
 it on.
> LED now conducts Via Q2 to bootm on C1 so sees Vin + Vcap.
> As C1 discharges brightness drops.

Thank you for that explanation!

> Mine, (which is standard voltage doubler) can use bipolars instead of
> FETS with due care.

What would be an advantage of going that way? I am under the (possibly
wrong) impression that a FET would be more suitable as it will have a
lower on Rds on.

Thanks!

Josh
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