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I'm trying to use a diffused RGB LED and a phototransistor (TEMT6000) to determine the color of a surface. I want to reflect red, green, yellow and blue light off a multi colored surface and determine a color at a point by measuring the intensity of the reflected light using the phototransistor. I will blink these colors one at a time of course. I'm trying to use an ADC to measure the amplutide of the output signal from my phototransistor. I'm testing with this breakout board from sparkfun (BOB-08688). My output signal will stay within VCC and GND. To avoid interference with ambient light I want to blink my RGB led at a TBD frequency, use a high-pass filter to eliminate the DC components (ambient light) and output only the frequency my LED will blink at. My output signal's amplitude should peak when the LED light is reflecting off a surface of the same color. How do I convert a signal with a constant frequency but a varying amplitude to a form where an ADC can accurately measure its amplitude? Thank you! |
April 22, 2020 |
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Your last paragraph sounds for all the world like a description of a detector for an amplitude modulated radio signal. You might be able to use the old crystal radio approach---diode rectifier to convert the ac to variable dc then measure that. |
April 22, 2020 |
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