What sensors should be used?

[FedoEET]

Hi I'm confused about sensors. I am currently doing my senior project and need to detect 4 black circles about 2 inches in diameter in a 6 foot by 6 foot space that is an off white color, with a border of any color. I can not go outside this border. I have been looking up sensors and can not determine exactly how it can detect whether it is looking at a circle or a line? Also I'm confused what sensors to choose. All all seem to do the same thing. Any help will greatly be appreciated.

 

[Klaus]

Supply more detail; from what distance do you need to sense the circles? Or is it a flat horizontal plane and your sensor has to move around it like a little robot?

 

[FedoEET]

More indepth

The robot has to move on its own starting in the lower left hand corner of the designated area. The sensors can be at any height, but I am thinking probably an inch to 2 inches off the ground should be fine. I am thinking of putting the sensors in a sleeve or something else to limit the amount of ambient light. The robot can not go outside the border line which can be any color. I was curious if there were any ideas of how circles can be detected and know that it is a circle and not the line. Also it is hard to determine what sensors to choose. I want to use maybe 3 sensors so that I can blanket the entire area in front of the robot.

 

[Ali Sajjad]

Wat is the purpose behind sensing these circles? If u are using this circuit with interface to a PC, a digital camera can serve the purpose. You can have the image scaned and compare it with a pre-stored image of the circle.

Further, if the circle is solid u can illuminate the plane from its back, and use a light sensor LDC etc. The light at the circle would be less in intensity and the sensor can indicate this change, but it can not inform the exact shape of that region.

- Ali Sajjad

 

[Burner_00]

All I can recomend buddy is using maybe some retro style IR optical sensors. IR emmiter on one side IR detecter(transister) on the other. try that out. If you need more assistance then drop me aline :wink: :wink:

 

[jem]

How about using three LED's of three different colors (say, RED, Green and Blue), and one (if you wish to do sequential measurements of the colors) or three phototransistors. You can calibrate the phototransistors's responses to distinguish between the black, off white, and colored border.