sonar or sharp IR ???

[benji]

hey guys i wanna do a robot that does 2d mapping,,and maybe later make it follow folks using the PIR ,,i checked some sharp IR sensors for the mapping issue but i found out that the ranges are very small,, not more than 1.50 meters ,,thats too short for what i want to build,, sonars give me a range of 6 meters.. coool,,but the problem is the spreading angle of the sonar,, as long as i wanna do mapping i want to have it just send its signal in one direction ,,stright line ,, can i achive it by closing the sides of the sonar with somthing? ,,? like two chops of alaminium or plastic?? possible? or is it gonna reflect the ultrasonic signal to the sensor and i have a mess ,,need help on this one

[Rebelgium]

If you'll cover the sides of your sonar sensor, you'll probably reflect the signal and your readings will be wrong.
Maybe look into buying more expensive Sharp IR sensors.

[benji]

well ive read about sonars that have a minimum range,, if i cover em within this minimum range,,would it still caue trouble?

[Admin]

What do you plan to map? What I mean is, what is your acceptable error (all sensors have error).

For example, if your sensor is 3 inches off, is that ok? Or maybe 2 feet?

It depends on what your robot environment is (size of obstacles).

[benji]

i would do mapping in a room , 2 feets error is way too much,,maybe be i can tolerate 2 inches or error
,,and is there sharp IR's with ranges to 6 meters? i surely dont wanna use only a 1.5 meter sensor.
low cost is also desired
and about the human detection thing, is it better to use a PIR or a thermal array?