Using the sunlight sensor module with an AdaFruit Feather M0 and currently only running the Demo example to verify functionality.
The visible light value hovers around 620 lm regardless if there is visible light or not. Placing my finger over the vis sensor does not result in any change to the vis lux value. However, shining my phone flash directly on the sensor does increase the value to around 740 lm, which does not seem correct as it is a dual-led flash, cant find the exact lm output spec.
The IR value starts off around 620 lm as well, but does fluctuate up and down depending on the scenario.
Finally, I did note that operating power is 3 - 5v, the feather only puts out 3, could this attribute to my faulty values? Does the sensor seem faulty?
FWIW, I just got a Grove Sunlight Sensor today. Using the example script with the sensor connected to a Seeeduino v4, with the sensor in a closed box (no light), I see readings of about 260 for Vis, 253 for IR, and 0.02 for UV. When I take the sensor out of the box and expose it to an LED shop lamp at about 3 inches, I get readings of about Vis = 400, IR = 1100, and UV = 0.75. Just looks like it has some zero offset.
Seems like sensor has zero offset value. Test the sensor in complete dark and store the values and then subtract the zero offset values.
I hope it will help you.