Light and color sensor response time

zhuzhix

Hello everybody!

We are interested in color detecting device, that can detect color of an irregular object, app. 2mm x 2mm x 2mm small at travel speed around 0.3m/s, then send signal to any controller. Minimum response time as I understand is around 1-3ms.
Also inspected sensor covered area must be as small as possible. I afraid that if covered area is big, result will be average color of base and color object, that will give wrong result.

Please give these properties for sensors:

TCS3200-DB Color Sensor and ColorPAL also.

Mike Green

For the field of view of the TCS3200-DB, please read the top of page 5 of the documentation. The sensor produces a pulse train whose frequency is proportional to the light intensity measured with higher frequencies corresponding to higher light intensity. The minimum response time is determined by the frequency since you need at least two pulses to determine a frequency.

Look at the ColorPAL documentation for information on field of view and speed. The ColorPAL's field of view is determined mostly by the tube that holds the LED and sensor. There's no lens other than those that are part of the LED and sensor. The ColorPAL uses asynchronous serial I/O up to 7200 Baud and requires several characters normally to make a measurement. That would take well over 3ms. Look at the documentation for details.

zhuzhix

Thanks for Your fast response, but actually I just understand that ColorPAL is not suitable for me, but what about TCS3200-DB. Can it detect any color in less than 3ms and what about blending colors? There will be moving object, so, what color will be exactly registered - what is the mechanism of detecting? I am just new to these sensors, but if they work, would be great.

Mike Green

I really can't answer your questions. You'll have to study the datasheets, understand how the sensor works, and decide for yourself. You have to make 3 readings, one for each set of color filters (RGB). The sensor itself is capable of providing 3 readings in under 3ms, but the resolution of the values depends on how long your controller spends counting the pulses. Maximum frequency is 600KHz at maximum light intensity. At 1ms per reading, that's a maximum count of 600 and you're unlikely to have that much light. As mentioned, a Stamp can't count that fast, so you're even more limited in resolution.

Phil Pilgrim (PhiPi)

Neither sensor samples the RGB color components simultaneously but, rather, in sequence. At the conveyor speed you've stated, you would be sampling three consecutive stripes, rather than a single dot. As such, I don't think either sensor would be suitable for your application.

-Phil