Adafruit TCS34725 showing very low values

Using Arduino Sensors
1

Hi, a newbie here. I am trying to use TCS34725 for a color detection project. When connected to Arduino uno, my sensor shows very low values.
Values should be between 0-65536 right? I am trying to calibrate it with black and white but I am not happy with the readings I get.

When in normal light condition my values are Color Temp: 4599 K - Lux: 54 - R: 76 G: 80 B: 64 C: 229
When exposed to black, Color Temp: 4600 K - Lux: 213 - R: 298 G: 313 B: 251 C: 925
When exposed to white, Color Temp: 4661 K - Lux: 3169 - R: 4160 G: 4520 B: 3571 C: 13214
I check my connections between the sensor and Arduino, they are all correct.

What is wrong with my sensor?

2

Your values are between 0 and 65536.

You haven't said what integration time you have selected.
You haven't said what "normal light condition" means - indoor/outdoor? There's about a 500:1 ratio between bright sun and indoor lighting so it really matters what
you mean...
I see the readings for white much bigger than for black, looks entirely sensible.

Can you post your code?

3

I am sorry about that. I am using the tcs34725 code that is in the examples of the "Adafruit_TCS34725" library.

I tested the sensor indoor.
Even though my sensor readings for white is much bigger than readings for black, when I divide them by 256 to get values between 0-256, I get RGB values like (5, 6, 6) for white. Then it is a little hard to differentiate between colors when I do color detection right?

#include <Wire.h>
#include "Adafruit_TCS34725.h"

Adafruit_TCS34725 tcs = Adafruit_TCS34725(TCS34725_INTEGRATIONTIME_700MS, TCS34725_GAIN_1X);

void setup(void) {
  Serial.begin(9600);

  if (tcs.begin()) {
    Serial.println("Found sensor");
  } else {
    Serial.println("No TCS34725 found ... check your connections");
    while (1);
  }
}

void loop(void) {
  uint16_t r, g, b, c, colorTemp, lux;

  tcs.getRawData(&r, &g, &b, &c);
  colorTemp = tcs.calculateColorTemperature_dn40(r, g, b, c);
  lux = tcs.calculateLux(r, g, b);

  Serial.print("Color Temp: "); Serial.print(colorTemp, DEC); Serial.print(" K - ");
  Serial.print("Lux: "); Serial.print(lux, DEC); Serial.print(" - ");
  Serial.print("R: "); Serial.print(r, DEC); Serial.print(" ");
  Serial.print("G: "); Serial.print(g, DEC); Serial.print(" ");
  Serial.print("B: "); Serial.print(b, DEC); Serial.print(" ");
  Serial.print("C: "); Serial.print(c, DEC); Serial.print(" ");
  Serial.println(" ");
}
4

Perhaps you should up the gain from the minimum value if you are using it indoors?

5

Divide by a smaller number, so that the maximum result you see in any color channel is 255.

Given these measurements:

When exposed to black, Color Temp: 4600 K - Lux: 213 - R: 298 G: 313 B: 251 C: 925
When exposed to white, Color Temp: 4661 K - Lux: 3169 - R: 4160 G: 4520 B: 3571 C: 13214

a good divisor could be 4520/255 (= 18, rounded up).

The integer division results are then:

Black R: 16 G: 17 B: 13
White R: 231 G: 251 B: 198

6

Hey, can you please explain to me what is meant by sensor gain? Why does setting it to 4X gives better readings?

7

Do you know what gain means? The sensor has a photo detector (or 3 of them I guess), and then a programmable-gain amplifier, then an ADC. Changing the gain swaps resolution for headroom in bright conditions.

8

Setting the gain to 4X should increase the values that you measure by a factor of roughly 4, all other things being equal.

The measurement noise (random variation between individual measurements) increases, too.

Lots of helpful and important information in the TCS34725 datasheet.

9

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