What i am doing bad? :-[
I was trying to calculate some lux values, but i have wrong results. I will explain what i am doing:
I assume that for most of the photocells: R(light) = 500/ Lux (KOhms)
On the other hand, Vcc x R(light) = Vo x (R(light) + R)
Vcc = 5V input of Arduino
Vo = Arduino analogue lecture in Volts (ej., a lecture of 412 is equal to 2.01171875 volts, as previously explained Mike in the previous reply to this post)
R = 3.3 KOhms (located in the circuit in the way to the LDR)
Then, following the equation proposed here: http://www.emant.com/316002.page
, the Light measurement (in lux units) are obtained from this equation:
Lux = (2500/Vo - 500)/3.3
When i apply it to the results obtained by the circuit, i obtain a decreasing lux when i obtain a higher lecture from Arduino on pin analog 0, what it is completely wrong according to the theory of LDR sensors.
So i don´t know what i am doing wrong in my calculations. I repeated it also in Excell to be sure that i was not doing it wrong by hand or with the calculator...