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Black colour sensor

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Rahulshah:

If the IR sensors aren't able to detect black, how come the ones already being used are able to steer a robot along a black line on a white course???

It seems the ones offering suggestions are not the ones failing to understand.

Perhaps you need to do some/more Google research on line-following as suggested previously........
 
BTW, why didn't you post the link earlier? Do want us to solve riddles?

To go one further step: You want the forum to serve a solution on a silver platter for your competition.

Not really nice!

I have posted the link earlier.....so please go through the discussion again if u want to verify.

I dont have to win a medal with help from here, i just need a basic idea to detect black blocks and rest I can manage it by myself.

And I will definately think over your suggestion....thanks again.
 
Rahulshah:

If the IR sensors aren't able to detect black, how come the ones already being used are able to steer a robot along a black line on a white course???

Perhaps you need to do some/more Google research on line-following as suggested previously........

As far as line following is concerned, I m going to detect white portion around the track, i.e. two IR sensors on two sides of the track. The same cannot be applied to detect the black blocks.

And thus my problem is not with the line following part but its with detection the black blocks. You can check out my simple line follower here which I made two years back.
Robotics tECHnOlogy Speak!!!
 
As far as line following is concerned, I m going to detect white portion around the track, i.e. two IR sensors on two sides of the track. The same cannot be applied to detect the black blocks.

And thus my problem is not with the line following part but its with detection the black blocks. You can check out my simple line follower here which I made two years back.
Robotics tECHnOlogy Speak!!!

In order to follow a line, your sensors detect both black and white, not simply white!

You have basically two identical sensing circuits, straddled across a black line. When neither sensor is above the black line, the drive to each motor is equal.

When the course (black line) deviates from straight, one sensor no longer detects white and actually detects black. The result of this is less drive is applied to the same-side motor, to bring the sensor away from the black and back to straddling the line, where white is detected by both sensors and equal drive is applied to both motors.

This is repeated all the way around the course. Many times..

So, the same sensors you are using already, are capable of sensing black, and do so all the way around the course........
 
Rahulshah, it seems to me that you can use the same technology for block detection as you use for line following. You apparently see a problem (or problems) that the rest of us fail to see. Please explain what you think the problems are.
Rahulshah, I posted this earlier. Please reply.
 
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Hi rahulshah,

I guess the track is not built up a way, that at intersections the path is populated with densely scattered black blocks. The track must be built up a way to always "see" if the vehicle is on track. (That's what I read from the article.)

I suggest you make a drawing scaled 1:1 and distribute black blocks along the track, keeping a minimum distance between course line and the blocks.

Then measure the minimum and maximum distance between track center and the contours of the blocks.

Eventually you'll find out a position where to place the sensors to keep not only the vehicle on track, but also don't miss any black block.

The basic idea has been given, and now it's up to you to run the whole nine yards and do the cake. :)

Of course, if the vehicle is a racing car - lifting two wheels off the surface in turns the reflective surface won't be perpendicular to the sensors anymore. :rolleyes:

If all wheels remain "on the road" the sensors will always remain perpendiclar to the surface. :D

Boncuk
 
there are crossings so you may need four sensors at all four corners of the bottom to track the path.
there are turnings so the distance of the cube may vary slightly, try to get maximum and minimum distances during this by the data provided, then you should make sure the sensed LED doesnt turn off before it passes the block.
consider at curves there wont be any perpendicular surface to reflect perfectly when passing white blocks. thus some fine tuning of sensitivity is required.
at gaps the field is too far, and can be recognised as black block, so you may need two types of sensors here, one is to detect there is an "object" and another one is to detect "no white surface", when both occurs at the same time only it should indicate sensed.
so both side of the robot will have to have 2 sensors, for both object sense and for intensity/colour sence.

use ultra sound sensors to detect black blocks/ to tell a object is detected and varify its white or black by IR method
as i told above to track on black line, you need two sensors on both sides to keep it on middle of the black track. when at a crossing two sensors may fail, since there is no white portion. so you may need to drive it straight in such instantces and may need another two sensors at the back too.
 
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use ultra sound sensors to detect black blocks/ to tell a object is detected and varify its white or black by IR method
as i told above to track on black line, you need two sensors on both sides to keep it on middle of the black track. when at a crossing two sensors may fail, since there is no white portion. so you may need to drive it straight in such instantces and may need another two sensors at the back too.

Exactly. It requires 2 sensor types. I would use the Sharp GP2xxx sensor to detect the block, it will work very well with both white and black and give you the distance.

Then use a very basic IR reflective sensor to see if the block is white or not.

I would point the Sharp sensor sideways to detect the side of the block and the IR reflective sensor pointing down to detect the top of the block. OR maybe swap them around depending on the size of the blocks and the construction of the course, whichever system works best. Generally the Sharp sensor is better suited to point sideways where it might get ambient light as they have good rejection of ambient light.
 
I guess it will be a problem accomodating two Sharp GP2D120 in the vehicle due to space problems.

They measure 40X13.5X13mm (LXWXH). Weight might also become an issue. (no weight info in the datasheet available).

Four CNY70 arranged at proper positions should suffice. Using six CNY70 the control circuit can be made to recognize tendencies.

Boncuk
 
on the website it says that readymade sensor array kits are not allowed. doesn't that just mean that you cant buy a kit which does the task already
 
Of course black is merely the absence of light. Most light sensors return a signal at the polar opposite of whatever signal they output for "full" white. Thus, black is well defined.

The biggest problem in a competition (at least in my experience with LEGO robotics), is inconsistent arena lighting, i.e., shadows, extraneous sunlight, etc.

SO, whatever sensor you pick, you'll be well advised to provide an artificial light source (or, preferred, find a sensor with an on-board light source) that's bright enough to overcome the above arena issues. This would be especially true for the side mount, cube identifying, sensors.
 
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