High Efficency Solar Powered Motor Driver
This motor driver deliver the power form capacitor to the motor when the capacitor is charged to 1.75V by the solar cell. After powering the motor, capacitor voltage will be discharged and the circuit will cut the capacitor-motor connection when the voltage drops below 1V, allowing the capacitor to be charged to 1.75V again to repeat the cycles.
The motor might run too often or even continuously if there is too much power coming from the solar cell, putting a 100K ohm resistor in series with the solar cell would overcome this problem. [Circuit’s schematic diagram source: Novotill’s]