can sonar module detect 7-6ft X 4-3ft object within 5-6ft distance ? is it possible? if it's impossible is there any solutions for this? please help me.. thanks. =)

It depends on the "sonar module", as well as the object you wish for it to detect. If the object has a smooth surface, then ultrasonic is usually a good option.

If you are asking about the Lego NXT Ultrasonic sensor, then the answer is no, it won't work. That range is too large. I think it's rated for about one meter, or about 3 feet.

However, there is a huge variety of ultrasonic sensors, so I suggest you look around for one that would work.

Please note than thread bumping is frowned upon, especially within 48 hours of the last post.

My LEGO ultrasonic sensor works accurately up to 5 feet or so. It detects hard surfaces better than soft ones. Also it performs best when pointed within 30 degrees of straight toward the object. I think you have a good chance of detecting it, but possibly only accurate to +/- 2in.