Dark side of the Force
Dark side of the force use a
single choke instead of a transformer for stepping up the voltage to
drive the leds. A CDS photo resistor senses when it is dark (on top of
its head). It is an adaption of the 1-cell boost circuit from Quantsuff's website.
The choke is a vintage toriod
from Torotel, marked P 30-55. It also is marked with a value of
360 Millihenrys. Thats a lot of inductance in such a small
package. Because of the high inductance, the oscillation frequency is
very low. Moving the artbot back and forth will show a
flicker. I ran out of white leds, so I used transparent red ones
instead. In the dark the eyes will start to glow. The
trimmer that forms the mouth can be used to turn down the brightness
and the current draw.
PDF of the schematic here.