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How to build a red, green and yellow color sensor?

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hi

How build a color sensor?
1- Red color
2-Green Color
3-Yellow Color
Can you help me?
 

color sensor using ldr

You have here 2 option. I should say 3 option but the third option will be to build a colour sensor by yourself is rather unrealistic.
So option 1: buy of-the shelf colour sensor, for example: https://www.lasercomponents.de/pdf/mazet/integral.pdf
Option2: use CCD camera fitted with a pinhole lens and RGB output and process these signals. If a camera doesn't have RGB output but only composite video you can always use external circuit which will extract R, G and B components from composite ..
 
color sensor.pdf

use one LED+LDR then

connect the LDR+resistor in series

use one ADC to find the value for corresponding colours
 
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    J

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how to build colour sensor with adc

In the previous post I told about LDR
but the LDR i am using is having a sensitivity of 3msec. That means time taken for output of the sensor to change when input light condition change.
So if you want a good sensitive one then go for

IR led+photo diode

This is having sensitivity in uS because u know that
LDR is resistor so the response is slow while photodiode is a semiconductor one that will be faster.
If you are using IR then there is also a good possibility of increasing range of device

I used to IR led+photo diode combination for my robot to detect edge of a table, In that i got the range about 5-7cm, but in LDR you won't get that much and also u have to apply an LED or any other form of light with it for good response.

Select which one is suitable for ur application
Remember that photo diode work only in reverse biased region. The configuration remains same

Photodiode(or LDR)+series resistor.
ADC connected across any of them as you wish
 

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ldr in color sensor

How about 3 sensors with 3 colour filters, and measure the relative output levels. You need a good consistant white light source though.
 

simple color sensor design using ldr

Just another thought, if range was not too great, or colour sensing does not need to be very precise. How about a tricolour led or even 3 discrete leds. You could then drive these with 3 MCU analogue ports and scan through the colour spectrum. You would then use a single photodiode to look for a peak response at any given point in the colour map. This is only a theory but may stand a good chance of working.
 

disadvantages of ldr sensor

I´ve seen this approach on robotroom.com, but if you only need 3 colors it would be better to use 3 filtered photodiodes (with a plastic or film of the color you want to sense over the photodiode) and a matching led of the color.

Of course you can always use a sensor like the ones from TAOS inc (though they are hard to get and the module that is sold in some stores is too expensive)
 

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    jgx

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colours sensors pdf

You can make color sensor with green,red,blue led and ldr.Output voltage of ldr in different led light is changing.You can test this output voltage with mcu has adc like pic18f458.
 

photodiodes or ldr

I think the camera can help you.
 

disadvantages color sensor

I used the CDD camera, it is very good.
 

sensor color led ldr

1. i want to ask whether LDR and sensor color is a same thing?
2. can LDR function like a sensor color?how?
 
ir based red color sensor circuit

Depending on how accurate your color sensor needs to be, you may be able to use a photo resistor, three LEDs (red, blue, yellow) and a microcontroller with an ADC

I built one for proof of concept for an M&M sorter that I never built.

The process was basically:

Shine each LED separately, wait for the photo resistor to even out, and get a reading

Compare the readings to determine the color.

My design was inspired by https://www.philohome.com/sensors/colorsensor.htm

The advantages are:
-Very inexpensive

The disadvantages are:
-Inaccurate
-The sensor needs to be somewhat shielded from ambient light (or programmed to compensate)

If I was going to do it again, I would probably substitute the three LEDs for a single (or maybe two) tri-color LED.

I am pretty sure that the source code I was using is lost, but if you want, I can take some pictures of the sensor hardware.
 
led color sensor

Isn´t it a bit complicated? Keep it simple.

The LED is not only light emitting but also light detecting.
So for the desired three colors: red, green and yellow take
LEDs- The beauty behind: They include the filter function ;o)
Some OpAmps and A/D converter and that´s it.

wolf
 

Re: ldr in color sensor

GrandAlf said:
How about 3 sensors with 3 colour filters, and measure the relative output levels. You need a good consistant white light source though.
Click to expand...
I want this attachment or more information about this sensor
 

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