There is one more way to achieve solar tracking. Use 4 LED's and LM339 comparator, than you'l be able to use those solar cells to generate power, instead of using them as sensors. I've built one my self and it works great, if you build one, don't get confused that the motor runs one direction when it's both sensors are pointed at sun, it's oscilating, so u need to change the value of R2, it's simple, because it is potentiometer. P.S. Sorry for mistakes at reply, I'm not using english daily. Edgars