Calculating intensity of a light bulb using LDR

Hey everyone,

I am very new to working with Arduino so I need some help.

I am working on a science project for which I need to measure the intensity of a light bulb from two different points. I have already created a circuit that uses LDRs and 10kΩ resistors to detect intensity. So far it’s working well and gives me analog values for the intensity between 0 and 1023. However, I need to convert these to actual intensity (more specifically irradiance) values in Wm-2. Does anyone know how that could be done?

Let me know if you need any more info, again I’m new to Arduinos.

Thank you!

Your LDR should have some specifications that may allow you to calculate what you want.
Find the datasheet.

The analog value allows you to calculate the resistance of the LDR.

If you don't have a data sheet that explains the relationship between irradiance and the resistance of your LDR, you will have to determine that, using a calibrated light meter.

Do like they do in the cal labs, use a reference meter or light source. If it is not in the units you want do the math and convert.

Photo diodes are linear and far less temperature-sensitive and much easier to calibrate than LDRs. Measurements are best done using more stable technology.