Black colour sensor

[rahulshah]

How can I sense a black color? I have to make a robot which can sense black colour cubes among black and white cubes and accordingly on sensing a black colour cube will lit a LED ON. Do I need to use color sensor using RGB leds?
Or is there any simple way to sense just the black color??

Please help soon....Thanks in advance...

 

[rahulshah]

Please Help Guys....

I need help urgently guys....pleaseeeeeeeeeeee

 

[3lectrokid]

i think you would need a camera. mabey a composite greyscale camera. you may need a bit of circuitry and a pic chip to decode the signals. as far as i know rgb leds are to make colours, not to sense light

 

[rahulshah]

isnt there any easy n cost effective way???

 

[Mickster]

Perhaps you could look at line-following robots.....

 

[KMoffett]

rahulshah,

What is the background color of the surface on which the blocks will be views?

Ken

 

[Boncuk]

You've got a problem there. Black and white are no real colours.

To differentiate between white and black you should think about reflection of light off a white surface. If reflection is expected and there is none it must be black then.

Boncuk

 

[amando96]

you're looking for something like this:
**broken link removed**
if the cubes are all at the same distance its even possible to detect "real" colours, but black and white are the easiest, as long as all the cubes are at the same distance!

 

[rahulshah]

rahulshah,

What is the background color of the surface on which the blocks will be views?

Ken

sorry, but i didnt understand ur question clearly............

but then too the blocks are completely black n white placed at irregular distances on one or both the sides of the track on which the robot should navigate....

 

[rahulshah]

@ boncuk
its possible to detect reflection of white blocks if all the blocks are adjacently placed.........but in my case the blocks are placed at some distance apart.....so even if no block is there, there wont b any reflection of light.....same is the case if black box is there....

@amando96
cubes wont b at same distance.....n wats the type of sensor image u have placed?

 

[Mickster]

A picture speaks a thousand words.....

Can you draw a picture (even in MSPaint) of the 'track' along with the placement of the black/white blocks. What colour is the 'track'...black, white or other?

Is the robot simply following the 'track' and lighting an LED when it discovers a black block?

How is the robot being guided around the track?

 

[rahulshah]

I have attached the rough figure of the arena.....the robot is a line follower type which has to follow the black track, which can be easily done using IR sensors feedback to DC motors.....but it has also to sense the black block n indicate sensing via visible LED....here the problem lies.

here is the competition link
**broken link removed**

 

[Mickster]

So the line-following robot is already using IR sensors to steer......

Why not use another set of IR sensors, mounted elsewhere, to simply light the LED's?

 

[rahulshah]

So the line-following robot is already using IR sensors to steer......

Why not use another set of IR sensors, mounted elsewhere, to simply light the LED's?

Its not possible with IR sensor to detect Black Color.....

 

[Roff]

Its not possible with IR sensor to detect Black Color.....

The background is white, and the other blocks are white. White reflects light. Black doesn't. All you need to do is illuminate both sides of the black stripe, where the blocks are potentially located, and have a sensor (phototransistor) that looks for the absence of reflected light. You can buy retroreflective sensor (Google) which have the emitter and the sensor in the same package. The output of the sensor needs to drive a transistor which drives the indicator LED.

 

[Boncuk]

I don't see any problem there. The line to follow is solid black, interrupted by a white area right and left of the track. White and black blocks around the track are of no interest at all - as well as the black track itself.

Focus the two IR reflective sensors on the white strip next to the track. If ever the IR reception is interrupted (leaving the centerline) you must apply an opposite steering command.

The CNY70 would suit perfectly for the task. Arrange the sensors according to the datasheet as close as possible over the surface. Make them adjustable in height for optimum line following.

Boncuk

 

[rahulshah]

@Boncuk

I think you havent understand the problem clearly....

Not only I have to follow the black line but also detect the black blocks and indicate detection using LED blinking.

You may visit the competition site itself.....that will make the things clear. **broken link removed**

Thanks anyways...

 

[Roff]

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.

 

[Boncuk]

@Boncuk

I think you havent understand the problem clearly....

Not only I have to follow the black line but also detect the black blocks and indicate detection using LED blinking.

You may visit the competition site itself.....that will make the things clear. **broken link removed**

Thanks anyways...

I guess I have completely understood the problem. (Did you?)

Use the sensors close to the centerline to keep track. Use the outer sensors to flash an LED, count the black areas or whatever is the task.

Arrange the sensors a way that even if the vehicle is off track the black areas will be "seen".

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!

 

[mbarazeen]

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.