search after distance meter​

 

Laser, or sound? Does it matter?

Laser will be quite accurate, but a 3 meters, you can get pretty accurate with ultrasonics.

Do a search for "rangefinder circuit".
Here are some promising results:
http://www.robot-electronics.co.uk/htm/srf1.shtml

http://www.circuitcellar.com/library/print/0103/piana150/index.htm

 

http://en.wikipedia.org/wiki/LIDAR

 

What is the minimal distance yo need to measure?

John

 

If you want to add an ultrasonic range finder to a project:
http://www.sparkfun.com/commerce/categories.php?c=84

If you want to build your own ultrasonic range finder:
http://www.circuitcellar.com/library/print/0103/piana150/index.htm

Build your own Laser range finders:
http://www.repairfaq.org/sam/lr/

Buy a laser range finder:
http://www.google.com/products?hl=e...esult_group&ct=title&resnum=1&ved=0CFEQrQQwAA

Or just do what I did and google:
"range finder kits"
"ultrasonic range finder"
"laser range finder"

 

@one 2 3 : Again, what minimal distance do you need to detect? There are even cheaper laser sensors than those in the above link, but we need to know the minimal distance to give a good recommendation.

John