Thank a lot to u guy, u all saved my life...Today the teacher come and check on the circuit and the teacher say it was good job...But the output of the 741 will be taken off as its going to the input of the mircocontrollor..At the same time the teacher gave me some problem or question..1 of them im still dont really know why...Teacher ask that when the force sensor (Ain) is lower than the Vref the output didnt went to 0..Also when its go higher then Vref its not going to 5V...I was stun when teacher as me that question..When lower than the Vref, for the 3V detect..The voltage at the output was 1.84 and the 3.5V detect was 1.54..When higher than the Vref, for the 3V detect the voltage go to 2.01V..and the 3.5V detect go to 4.85V (for the 3.5V i think should be ok)...Do u guys know why?..Also i using 2 different IC...1 is HA17741 and the other 1 is UA741CN....