Plant monitoring project

for the first project i am getting 1.02 thousand constant value and when i put finger on LDR i am getting 771 value…i have attached the csv file also…`


What is the value of the resistor that you have used in the circuit with the LDR?

Restart your bolt module & try to change the light intensity falling on that LDR.

I’ll suggest not testing it in the open.
keep it in a room. switch on lights and deploy.
now switch of the lights and deploy again.
now see the table. u’ll see the change. if not. try reconnecting the product.

You must have used the resistor with 10kohm rating try increasing the resistance, and remember LDR is not sensitive at high intensities so it will never work outdoors

Do refer this website to calculate your resistor value::point_down:

As in bolt kit, there are 2 types of resistor available.

I also had faced through the same issue: In order to get a fairly sensitive light detection using LDR, it would be great to use a resistor having lower resistance values than 330k(ohm), as higher the resistance connected to LDR, we will need more less light(darkness) to get the average readings/values desired. ( Still the readings/values that you get from the sensor depends on the lighting in the room).

You may have a look at this video which may give you an estimate:

If there is some correction to be done then please do correct me.

Good luck! :+1:


Try to keep the module inside a dark room or switch of the light when it’s dark. You might get different readings. When I covered it with my hand I too got 1.02 thousand and then I tried keeping it in a dark room and it worked. Note that you need to deploy the values after a minimum time gap of 20 seconds.

check the resistor and do it again in dark room and change light intensity

You better try it in dark room

I have also been facing the same issue for quite a long time.
Thank you for the explanation.
It works.

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i was also facing the the same issue, then i reconfigure the resisters (means remove the resisters and then again put it in keeping in the mind that the 3V3 pin connected to LDR doesn’t touch resister groud pin hand) then i restarted and look at the results after 10, it going perfect, try it.

Apart from varying the intensity of light falling on the LDR and making sure that the 3v3 pin connected to the LDR doesn’t touch the ground pin or any wire coming out of it, you can try using the resistor which looks like this :

This is the 330 ohm resistor. Instead of using the 10k ohm resistor, use this one. Hope this helps!

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I faced the same problem, Thank you your suggestion helped.

Thanks! It really helped me as I was trying for half an hour and worrying why I am getting only 1.02 thousand. By just changing the resistor everything worked fine.Thanks a lot for your help.

Try to change the intensity of the light.
Keep it in a room and try it once by changing the intensity of light.
Check the connections properly.
Remember that the intensity of light is inversely proportional to resistance of LDR
Hope it works.
Good luck.

Put resistor with your sensor and the value you got 1.02 thousand. it’s a highest value of light 1024.and when you put your hand on it, sensor got sense different brightness as it has a interface of your hand. so your project is successful.

Just try to turn off your room light and also try with flashlight of your smartphone and also try with different brightness of your phone. You’ll get some different value everytime

You may have a look at this video which may give you an estimate:
And also make sure you connect the resistore properly

See , from what I understand , the basic question is that you are concerned about the constant values !!
Do not worry , actually you might be in a room having some form of artificial light , that is why u r getting a constant value . First of all check if on placing your finger on the LDR or switching of the lighting there is very vast change in your data readings , and see if on keepng the lights off the value again becomes constant or have negligible difference !!,
This is because resistor you are using is of 10k value . By voltage divider law we know that greater the resistance more is the voltage , this implies that there is more voltage difference in the resistor than at the LDR . Since input is fixed at 3.3 V , this makes that the voltage across the LDR low and hence it makes it more sensitive to smaller currents, Since the artificial lights give off same intensity continuosly the voltage value remains the same .
On the other hand , if you use a 330 V resistor , actually the system becomes less sensitive to the current values , but the value of voltage across LDR due to the fact that now more current will flow overall in the circuit , makes the voltage values you see more prominent .
Since in case of 10k , even a smaller value of current could make the LDR reach a high value , using a 330 ohm resistor would make the small changes in volatge readings more prominent as comparitively higher current will flow .

Now just remember , how to make the correct connections !!!