TCS 34725 color offsets

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prateek3005
 
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TCS 34725 color offsets

Post by prateek3005 »

Hi.

I bought the adafruit color sensor TCS 34725.

My project is to develop a textile color scanner. So i arranged the set up as shown in the image.

I am facing a problem with sensing extreme values like Black #000000.

The other problem that i am facing is while i am able to get close hex values for warm colors like Fire Red #9C2A00 but there is a large offset when i test colder colors like Old Port #008eb8. There seems to be greater offsets in Blue and green than red.

There aren't any calibration services around here. Looking for some suggestions with this

Best regards

Prateek Khare
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adafruit_support_bill
 
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Re: TCS 34725 color offsets

Post by adafruit_support_bill »

What are you measuring and standards are you expecting to match?
Reflected light readings depend not only on the color of the sample, but the color spectrum of the light source you are using.

As for measuring black. You would need a 100% non-reflective target to measure 0000. Such targets can only by approximated in laboratory conditions.

prateek3005
 
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Re: TCS 34725 color offsets

Post by prateek3005 »

Light source is only the LED on the sensor board. As can be seen in the photo attached with earlier post, the sample threads are brought in close proximity of the sensor (roughly 0.5 cm). The sensor being completely covered while taking the readings has only its own light source in use. There's no stray light in play.

Is there a way to switch off the LED so that i could try using other sources as well?

Whats the purpose of the INT pin?

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adafruit_support_bill
 
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Re: TCS 34725 color offsets

Post by adafruit_support_bill »

As can be seen in the photo attached with earlier post
Unfortunately, your attachment was not in any known image format. Please post as a JPG.
Is there a way to switch off the LED so that i could try using other sources as well?

Whats the purpose of the INT pin?
See "Interrupts and LED control" here: https://learn.adafruit.com/adafruit-col ... program-it

prateek3005
 
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Re: TCS 34725 color offsets

Post by prateek3005 »

Sensor with enclosure
Sensor with enclosure
WP_001076.jpg (116.52 KiB) Viewed 478 times
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inside the enclosure
inside the enclosure
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Testing sample
Testing sample
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adafruit_support_bill
 
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Re: TCS 34725 color offsets

Post by adafruit_support_bill »

That looks like a good setup to avoid stray light, so your measurements should be repeatable.

But you have not told us exactly what measurements you are trying to match. Do you have some standard color samples? Do you know the conditions under which they were measured?

Trying to match the color spectrum of a reference light source is not so simple. Especially when using LEDs - which do not have a continuous blackbody spectrum like most incandescent lamps.

The most practical approach would probably be to produce your own calibration tables. If you measure your reference color samples, you can produce a table which maps the raw-readings to your standard values.

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