hi,
i am making a feature in a robot which would measure the distance from other robot by sensor which i have completed, the thing which i am still stuck is how to made a circuit which will measure the distance of another robot and show it on 7 segment display can anybody help please wanna made asap.

 

What range? Sharp makes some nice IR Rangefinders.

 

range is from 0-50 meters.

 

From what I saw regarding rangefinders ultrasonic time-of-flight solutions are generally limited to 10m or less.
Stores dedicated to robot amateurs have plenty of US rangefinders that can be used for this scope with a budget under $ 100 (http://www.junun.org/MarkIII/Info.jsp?item=32).
Years ago I read about a sensor kit from kodak that was working up to 25m or so, but I cannot find the part number in this moment.
If you need to experiment with ultrasounds, maybe you could play around one of those ultrasound "measure tape" that sells at home depot for 30$ or less.
Infrared reflection rangefinders are generally cheaper and they have usually better resolution/stability, but their typical range is few inches only. Sharp has a wide range of similar products.
Finally, when you need larger maximum range, and maybe an improved resolution and stability, laser interferometers can do the job, but be prepared to more expensive prices.
Jenoptik LDM41 (http://www.jenoptik-los.com/cms.php?pageid=812&lang=1) is a compromise solution that uses a swept frequency LASER modulated interferometer to measure distances up to 100m with a sub-millimeter resolution. As far as I know, the budget is around 3,000 $. More sophisticated interferometers can bring resolution down to 1 micrometer or less, but with exploding budgets.

 

Take a look here at "Ultrasonic Range Finders" or "High End Scanning Lasers and Obstacle Detectors"

http://www.robotshop.ca/sensors.html

 

These sensors you guys are recommending will only tell a distance of an object... this will of course include any object within the sensors range..... Maybe if used with some kind of IR beacon on each robot so the other robot "knows" it is another it is detecting and not just a wall.... So if 1 bot detects say a 38Khz modulated IR signal, it can then look at the "distance" sensor to figure out how far the other bot is....

My .02

 

These sensors you guys are recommending will only tell a distance of an object... this will of course include any object within the sensors range..... Maybe if used with some kind of IR beacon on each robot so the other robot "knows" it is another it is detecting and not just a wall.... So if 1 bot detects say a 38Khz modulated IR signal, it can then look at the "distance" sensor to figure out how far the other bot is....

My .02

You are right.
I apologize. I understood that the problem was measuring the distance, and I did not focus on the fact that the other robots are the targets. Sorry