INDEX

This is another good model

Here LDR4 and LDR3 are subtracted and this output is used to drive motor for one axis. LDR1 and LDR2 are subtracted and this output is used to drive motor for other axis. Making mechanical model is one of the tough job. The thread arrangement is not so good. You should use another arrangement. One axis we should motor should carry the motor and other mechanisms for the other axis. So the first axis motor should be of good torque enough to rotate the other axis mechanisms. If you use pulley arrangement for the main axis(the axis at low level) then the probability of slackening is there because of the weight of the motor of the other axis and it should rotate 180 degree. So the force will be there. In all these circuit we should first arrange the sensors readings first to make solar panel
perpendicular to sunlight. This is a tedious task. You should require a magnetic compus to align the sun tracker in proper direction, i.e for determining north,south,east and west direction. You can use the comparator circuit with a relay to switch OFF the power supply to the motor and the remaining control circuit when the light  intensity if less. This condition exist in night and rain conditions. In that case light will be less , the difference between effective power we receive and we spend on
turning the tracker will not be good.Suppose the condition when sun set at west and next day tracker should start from east, then also this circuit work.