Page 48 - Robots Androids and Animatrons : 12 Incredible Projects You Can Build

3.4 Complete solar engine

this circuit is rated at 2.5V, but I’ve seen it charge a capacitor up to
4.3V under no-load conditions.
I’m sure some people planning to build this circuit are already
thinking about adding a few more solar cells to speed charging.
You should not do this. Adding solar cells will increase the cur-
rent and will speed charging for the first cycle only. In order for 27
the circuit to recycle, the current through the SCR must stop
(or at least be very minimal) for the SCR to close. If there is too
much current being supplied by the solar cell(s), the SCR will
stay in the on condition. If this happens, the electric energy
from the solar cell will continually flow through the SCR and be
dissipated. Electric energy will not build on the capacitor, and
the solar engine circuit will stop cycling.
The components used in the circuit are balanced for proper oper-
ation. One component you may change is the main capacitor. You
may use smaller values for quicker charge-and-discharge cycles. A
larger capacitor (or capacitor bank) will store more electric
power and perform more work, but be aware that when using
larger-value capacitors it will take that much longer to go through
the charge-discharge cycle.

Uses
A solar engine circuit may be used in many novel and innovative
ways: as an onboard power plant for a solar racer, to supply power
to a relay station, as a flashing light-emitting diode (LED) buoy, as

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