Hi junkers !
This time I have managed to build a solar robot which completely uses solar energy to drive itself.A solar battery is not that simple to drive a motor as it seems to be because small solar cell have low current rating in addition to variable voltage proportional to light intensity.the voltage of a solar cell drops when it is connected to load implies it has a very bad regulation for high loads , the voltage developed for low intensity light is so less that it cannot drive a motor hence a circuit is used so that it stores energy in a capacitor and when sufficient charge is stored it should release it instantly so the schematic shown below does the same it's called the "solar engine"
WORKING: Initially the capacitor is at 0V and transistor Q1 is in cut-off state ,when the cell is exposed to light the capacitor starts charging up to a voltage of 0.7(cut in Si transistor) Q2 + 1.67*n(cut in FLED Red LED)(n = number of LED's)when the capacitor charge's above 0.7+1.67*n transistor Q2 come in conduction and supplies base current to Q1 through 2.2K .Thus Q1 is now in conduction and the motor turns as the capacitor discharges to 0.7V again Q1 and Q2 are in cut off and capacitor again charges and the cycle continues .
