9
THE TRACKER CONTROLS
The heart of the
Tracking Solar Oven is the
electronic control. A Very
simple control may be built
from a photo diode
(Electric Eye) and 12 volt
DC relays. Most of the
parts are available at local
radio parts stores.
The photocell battery
charger that works well is
the new thin film, glass-
encased type that produces
18 to 20 volts and
measures only 6 inchs
square. The batteries are
simple AA nickel cadmium
rechargeable cells in series
to produce 12 to 15 volts
at 50 to 80 milliamperes.
The photo diode
(Electric Eye) is really a
photo-transistor using only
the emitter and collector
leads which conduct electricity in the presence of light. A simple shadowbox will shade the electric eye
when the oven is focused on the sun and will cause the motor to stop. At first, the photo diode is far too
sensitive. To adjust the sensitivity black silicone can be dabbed over its surface then removed with a
toothpick until it responds only to direct sunlight. The reset switch will send the motor into reverse until
the sunrise switch is tripped. The oven is now positioned for the next day. A wind-up 12-hour timer
switch on the reset switch will allow timed cooking; it sends the cooker to the sunrise setting when done
and even sounds a buzzer.
Conventional solar trackers are available and can be adapted for use on this or almost any other solar
cooking oven.