RAKS

Colour sensor is an interesting project for hobbyists. The cir- cuit can sense eight colours, i.e. blue, green and red (primary colours); magenta, yellow and cyan (secondary colours); and black and white. The circuit is based on the fundamentals of optics and digital electronics. The object whose colour is required to be detected should be placed in front of the system. The light rays reflected from the object will fall on the three convex lenses which are fixed in front of the three LDRs. The convex lenses are used to converge light rays. This helps to increase the sensitivity of LDRs. Blue, green and red glass plates (filters) are fixed in front of LDR1, LDR2 and LDR3 respectively. When reflected light rays from the object fall on the gadget, the coloured filter glass plates determine which of the LDRs would get triggered. The circuit makes use of only ‘AND’ gates and ‘NOT’ gates.
When a primary coloured light ray falls on the system, the glass plate corresponding to that primary colour will allow that specific light to pass through. But the other two glass plates will not allow any light to pass through. Thus only one LDR will get triggered and the gate output corresponding to that LDR will become logic 1 to indicate which colour it is. Similarly, when a secondary coloured light ray falls on the system, the two primary glass plates corres- ponding to the mixed colour will allow that light to pass through while the remaining one will not allow any light ray to pass through it. As a result two of the LDRs get triggered and the gate output corresponding to these will become logic 1 and indicate which colour it is.
When all the LDRs get triggered or remain untriggered, you will observe white and black light indications respectively. Following points may be carefully noted :
1. Potmeters VR1, VR2 and VR3 may be used to adjust the sensitivity of the LDRs.
2. Common ends of the LDRs should be connected to positive supply.
3. Use good quality light filters.
The LDR is mounded in a tube, behind a lens, and aimed at the object. The coloured glass filter should be fixed in front of the LDR as shown in the figure. Make three of that kind and fix them in a suitable case. Adjustments are critical and the gadget performance would depend upon its proper fabrication and use of correct filters as well as light conditions.

View Circuit. Click Here.

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Hero999

There's nothing wrong with that project, it will work.

However it is a bit complicated, I'd go with an RGB LED, a quad op-amp and a microcontroller.

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Klitzie

Hero where can i find the RGB led, a quad op-amp and a microcontroller color sensor can you post the link..thx

Krumlink

Are you KIDDING me.

Are you honestly that lazy? for god sakes there is most likely a search bar right next to your browser! Even then you can go to google!

If you GOOGLE it, you can find it. wow.

And just in case if you are that dense:
www.jameco.com

Then search for it in the Keywords bar.

Good job!

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MechTronics

Rupesh puri

it works?????
i dont think so............

Hero999

Have you tried it and had problems with it?

If so please post the schematic and code so we can see what's gone wrong.

If not could you please explain why you don't think it'll work?

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Super_voip

It would only be useful for emitted light the LDRs usually aren't sensitive enough for reflected light. The original post was just a cut & paste from the web site.

Klitzie

Im building a ldr sensor based on society of robots only that i used blue and red super bright leds. The output is feed to adc0804. The adc0804 output is being feed to a 74ls244. I used leds to indicate the 7 output data.

The Problem is the data changes every single seconds when the blue box or red box is being placed within the ldr's light. The blue and red super bright leds are all turn on.

Just need an advice because the someone from this forum says its absolutely works? maybe i didnt get the instruction right....thx

Gordz

I have used the ADJD-S313 colour sensor from Analog Devices for this sort of thing and it is pretty accurate, small and easy to use. Check it out on their website.

erosennin

There was an article in Silicon Chip (June 2005) - an Australian Electronics Magazine, they used the TCS230 device.
See Link

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gramo

Thanks for the link, I was looking for something similar myself

Nice device, I'm going to have to have a play with one.

I suspect the output from these devices would be much more linear in comparison to RGB LED's and opamps

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Hero999

Just another thought but if you use an array of LEDs then you might and you're using natural light for illumination, then you might want to consider adding some sort of variable gain stage. Perhaps another light sensor like an unfiltered LDR which can be used to detect white light and adjust the gain of an amplifier acording to the brightness of the ambient lighting.

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futz

I just ordered one of these from SparkFun. It has an Avago ADJD-S371 sensor on it. Should be interesting to play with.

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