Big D
Big D is a Mosfet Joule Thief with a
CDS
photo resistor for turning on at night.
Watson's
eblog and
Quantsuff came up with the idea of
using a low turn on voltage
mosfet. I found a Supertex
TN0702N3-G device that fits the bill
at Mouser.
The device has a low turn on
resistance for delivering lots of current to the led. This one is
a blue-green led from Electronic
Goldmine.
Magnets are used to attach the Joule
Thief to the battery. The battery lays on little stick-on bumps
attached on a base. You can use AA, C or D size 1.5v cell to power the
Joule Thief.
The core is a Fair-Rite
2643002402. You can get them from Mouser
for
13 cents.
The circuit is wired up on a small piece of perf board.
Six turns of two wires passes through the core. Use wire from
ethernet cable.
During the day it rests with very low
battery drain
PDF of schematic
At night it lights up like crazy
