@NickM95 Yes. If you use a 10 ohm resistor it´s right. At high levels of radiation, It will be 200 mA and V in resistor will be 2 V and this value is far from Vmp so it can be considered Isc.

Then, if you have e.g., 1.5 V, you´ll have a radiation level of 750 W/m2 . 

What we obtain from ADC is a value "k", wich varies from 0 to 4095. 0 is 0 Volt and 4095 is 3.3 V. 

If we want measure volts, we only have to use this :  V(volts) = k / 4095 * 3.3

In your case, once you have measured volts, yo do this : rad = 500 * V(volts) = 500 K / 4095 * 3.3 = 0.4030 * K

"500" is the conversion factor from Volts to Radiation, because 2 V represents 1000 W/m2 in your case.

Edited May 13, 20206 yr by Javi Martínez

I’m thinking of making something like this to test different parts of my roof for solar radiation before I install solar panels on it... but I am a complete noob when it comes to this. I can buy stuff and put them together, but would really appreciate if you could help me to put together a shopping list to get this going! I’d probably like to build three of the same ones, to concurrently test the different roofs I want to try...