how i could build a sensor, which can point out the distance between the sensor and the obstacle. what type of sensor should i use??can i get a help please!! :)
I hope you are talking about something like this >> S1 --------- | << and you want to calculate the distance of the object? if so then you can use IR for that maybe this link can help you:
An IR sensor will do the trick for you. The time taken for overall journey will give you the distance between the sensor and obstacle
Use either an IR sensor or Ultrasonic Range detector. I would personally recommend the Ultrasonic one. If you want help in arduino, definitely ask me.