the schematic for the solar engine. Here's how it works. The solar cell charges the main 4700 uF capacitor. As the capacitor charges, voltage level of the circuit increases. The UJT begins oscillating and sending a trigger pulse to the Q1. When the circuit voltage has risen to about 2 volts from the main capacitor, the trigger pulse is sufficient to turn on the Q1. When Q1 turns on, this turns on Q2 the 2N3906 transistor through the 2.2K resistor. The 2N3906 keeps the 2N3904 turned on until all the store power in the main capacitor is dumped through the 2N3904 and the high efficiency (HE) motor. The motor spins momentarily as the capacitor discharges then stops. The cycle repeats.