Regarding light monitoring data

I have completed the first project of plant light monitor and have received the data of light monitoring. it is attached in this link=

I didn’t understand the values it showed up. Can anyone tell me about that? thanks in advanced.

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@ajundre321 The value shows amount of light falling on the sensor. Higher the value means more light is falling on it. And when you get low value it means that amount of light is less. You can try by switching off all the lights at night you will get output between 14-15 ,it all depends upon amount of light it receives. If this is not the answer and you expect something else then please ask!


thank you so much @divya19. I got my answer. for curiosity what should the highest value?

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and what about the intensity of light? Can i get it directly or have to do programming?
what is the unit of this value showing in data ? is it voltage or resistance?

1.02 thousand is the highest value when you try using torch🔦 or flashlight according to my experience.
Intensity of the light you get directly by writing single line code in which you take A0 as input .Here the input is intensity of light that ldr reads as A0 pin is connected to one leg of ldr. That analog voltage is then converted to digital value which you get as an output.


light intensity is shown in units of lux. The formula that you can follow is
resistance=500/lux. the voltage is being calculated across the ldr thus by voltage divider formula you can find the resistance. This is probably the way it is working. and the program is just the one line code mentioned.

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just connect a led in the same points u have connected a ldr(use breadboard) and try to cover ldr with something u will see the brightness of led goes changing when u do it.

Even i got 1.02 thosand exactly, well by using mobile torch light…
can we get more than that ?

It is probably because ldr is an analog sensor of 10 bit value in which the data can fall between 0-1023. The ldr provided might be having a maximum set to 1.02 thousand. Therefore, light falling on the ldr beyond a certain limit is read 1.02 thousand only.

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Yes @rickan.datta . I also think that there must be something more to the programming.
Dear Bolt team,

  1. Can you share the specifications of the ldr that you have supplied with the kit?
  2. Please confirm if only writing “light” in the second column converts changing voltage of ldr into
    lux unit. Is there any other formula for it?
  3. Resistance = 500/lux is the value which I also got after googling for the subject. Is this value correct?
  4. Written below is the formula I could achieve so far. Still I need to know the current value to get to Lux. Please help in this matter.

IR= I X (R1+R2)
3.3= I X (R1+10000)
3.3 = I X ( 500/LUX + 10000)

The values that have been recorded indicate the intensity of light falling on the sensor. You will get a lower value in a dark room (around 15-20) and get a very high value when you keep the sensor under the light of a torch or flash light (generally 1.02 thousand, which is also the highest value recorded by the sensor).

@ajundre321 hi I am Tanmay and what I observe 1.02 highest value in home light conditions and shadow in-home light conditions average 600 - 700 and in dark this value decreases 200.

Increasing the frequency of the light without changing the number of photons per second is one way to increase the intensity. In another way,yes we can get more values .

Here in data table, intensity of light is shown by which we can easily conclude that when light intensity is High , resistance of LDR is low and voltage across LRD is also low (using ohm’s law V=IR) and when intensity of light is low then resistance of LDR is high and voltage across LDR is high.