INDEX

6. The sensitivity of the LDR is another factor. I got up to 3ms, but that is a rare condition. When come to practical it will go around 10ms or below. So this is another factor. If you use IR with photo diode then you will get good sensitivity.
7. There will be problems with external light. This problem will be too much with the above circuits. IR will provide a better performance to external light, but they also have some effect. You should provide a good source of light with the sensor like LED+LDR, but to get good performance use a source of light with good brightness. If the brightness is good then better will be the sensitivity of the LDR and the adjustment work will be somewhat reduced. I am talking about the light on the robot. You should make the external light effect to be as small as possible. So provide a good source of light on robot itself. When you provide a good source of light, it will increase the weight of the robot and the power consumption of robot and the requirement of the number of batteries.
8. Better keep the LDR+LED combination to be less affected with external light. The way you use will affect the performance of the robot.
9. See something about positioning sensors

 Here you can see that robot is going forward to take the turn. This will increase the time for the journey. This should be avoided by putting LDR in the front of the robot. Put sensor in the front, so that normal bending occurs without loosing time. But you should see the effect of external light in that case.

So in order to attain good speed use good motors(motors of good rpm,see the motor he used http://www.robotroom.com/Jet.html). The second thing is to reduce speed so that the robot will not stop for all bends. If you increase number of sensors then the response will be good because we
won't stop the motor for all bends. The above circuit stop the motor for all bends. For small bends we should have to reduce the speed of one motor very less,so that bending will occur fast. If the bend angle increase then the voltage of one motor should remain same, while the other should be decreased so that turning will occur. The greater number of sensor the more accurate it will be. Now let's talk about controlling motors. The two ways are varying the voltage and PWM.