Grove Light Sensor

Products & Technology Grove
#1

Hello all,

  1. I placed the grove light sensor in my office (12 am with sunlight) and I was getting 613. I placed it out, under direct sun (at 30 Celcius degree) and I got only 630.
    Is this normal?

2.Also, the output of this sensor is then converter via a math equation in resistance. On your wiki page, I am reading that the physical meaning of this resistance is to be exported from the the resistance curve, which to my opinion is rather vague.

  1. What is the max length of the cable in order to read correct values from this sensor?

Thank you very very much in advance!

Alexandros

#2

I think it’s normal, maybe the linearity of this photoresistor is not good enough.

#3

wow, if the stable is longer, the value will smaller, anyway, it’ll have some change , so you can judge the light is strong or week…

#4

Hi,
Similar issue here.
Daytime light caps around 610-615, even direct lightning from a strong LED doesn’t help.
Practically, it matches moderate light , just good to read at night.

grove_light_sensor_v1_2.py says maximum value is 1000, though I can’ t get over 615.
This looks like there’s a power voltage mismatch, ADC expecting max 5V and LED giving 3.3V
3.3V/5V is 615/1000

But adc.read_register(0x29) gives 3.28V.
read_voltage gives me 2V, so I’m not sure what’s going on but the ratio is very suspicious.

[Well, I hadn’t realized OP was from May 13th… but 2013!]

#5

Hi @cbaisse
Do you strictly follow the wiki process? In addition the light sensor value only reflects the approximated trend of the intensity of light, it DOES NOT represent the exact Lumen.

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#6

Hi,
Yes, even using the sample code from the wiki, I can’t read values above 615.

My problem is that it correspond to a very moderate amount of light - (barely suitable for reading, I’d say about 100-1000 lux).

Anything above that saturates the sensor, so I can not differentiate higher light values.

#7

Hello @cbaisse,

I use my sensor with a Grovepi and under a simple table lamp I measured 756 right now, and I received even higher data too. However it must be stated, that it is hard to get values close to the maximum. It is also have to be realized, that this cheaper kind of sensors are rather for distinguishing dark/shadow from light or day from night, than for fine measuring of light values.