This is a circuit of battery less fm transmitter, circuit is same as we discussed before in "Best FM Transmitter Topic" but we changed the power source from 3 volt battery to solar cell. The circuit will work in direct sun light, use small solar cell of 3 volt to 5 volts 100mA and also experiment with different types of solar cell of 3 to 5 volts or above in direct and indirect sunlight. For more details about circuit please see the topic page "Best FM Transmitter".