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[SOLVED] Flash sensor lux calculation

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ponnus

ponnus

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Hai,
I am using APDS 9300 light sensor for lux calculation. This sensor have an I2C interface which gives the ADC readings of the sensor. I am reading these values using a microcontroller. It has two channels: CH1 reads only IR, while CH0 reads IR and Visible light. When I used it inside the room, I found that CH1 reading(IR only) is less than CH0 reading, and when i used it in bright sunlight, I got greater IR reading.
But, when I calculated the sensor lux, using the formula provided in the datasheet, I am getting smaller lux, ie, below 15.
The formula for lux calculation is:
Code: 
For 0 ≤ CH1/CH0 ≤ 0.52, Sensor Lux = (0.0315 x CH0) – (0.0593 x CH0 x ((CH1/CH0)1.4))
For 0.52 ≤ CH1/CH0 ≤ 0.65, Sensor Lux = (0.0229 x CH0) – (0.0291 x CH1)
For 0.65 ≤ CH1/CH0 ≤ 0.80, Sensor Lux = (0.0157 x CH0) – (0.0180 x CH1)
For 0.80 ≤ CH1/CH0 ≤ 1.30, Sensor Lux = (0.00338 x CH0) – (0.00260 x CH1)
For CH1/CH0 ≥ 1.30, Sensor Lux = 0

These are some readings I got in sunlight:
Code: 
[B]CH0(IR)           CH1         CH1/CH0          Lux[/B]
5047	           4881	0.967109174	  4.36826
5047	           4700	0.931246285	  4.83886
5047	           4697	0.930651872	  4.84666
5047	           4623	0.915989697	  5.03906
5047	           4596	0.910639984	  5.10926
5047	           4588	0.909054884	  5.13006

I am reading the correct channels. Sometimes, I am getting zero lux. When I googled about the lux, it says the lux in sunlight is in 1000s.
Does anyone know about this? Please help me...
 

APDS 9300 calculated lux is very low

Hai,
I'm using Tint(integration time) of 13.7 ms and gain is 1x. So I'm getting maximum CH0 value as 5047 in bright sunlight. The datasheet is not specifying the nominal conditions in which the empirical formula has to be applied.

I also read the datasheet of TAOS TSL2550.In this, the formula is for Tint=402 ms and Gain=1x

When I googled about normal lux values in daylight, it is very large. But I'm not getting a lux value more tha 15.

Thanks
 

Re: APDS 9300 calculated lux is very low

Hai,
I think I've to take more readings with Tint as 101ms and 402ms.
Because, I've taken the readings using Tint as 13.7ms, and in bright sunlight I got CH0 value as 5047,which is the maximum value in this case.
There is a scale factor given for each of the Tint.So I divided the results with the scale factor (.034 in this case) and I got a larger lux value.
 

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