Im back after a while. As you suggested i tried to build $50 robot on prototype board and facing some strange issue. Before that please see my cabling on breadboard..I also modified code little bit (to debug the issue)..
if(sensor_left > sensor_right && (sensor_left - sensor_right) > threshold)
LED_off();...rest of the code
else if(sensor_right > sensor_left && (sensor_right - sensor_left) > threshold)
I purposely made LED_on in last("go straight") else condition and LED_Off in "turning conditiion" to check the circuit and code. I found that when im not attaching survo but just "on" the circuit to run the code..my LED shines in normal light condition (i.e. when light is equal on both the sensors) but when i move my hand on one of the sensors..(I tried both left and right) LED turns off that is to prove that my circuit is correct and so is the code in ATMEG8.
But as soon as i attach my servos (modified for full rotation) nothing works..servo just makes strange noise and thats it..sometimes one of the servo rotates and then stops...i am having no clue what is wrong here but my servo looks ok..
and one more thing to mention is when I attach even one of the servo voltage drops straight from 5.02 to 2.2~ Volts and im not sure why its happening
Can somebody help me debug the issue?
Im using 2.2Kohm resistor for my photoresistors and i calculated them using the method you mentioned and also using the excel sheet to see voltage drop difference..
You tube video of my running circuit is here (w/o servo attached)MVI_1001.AVI