reading solar panel voltage

Hello guys, I wanted to read a 3w 12v voltage using analog. I use a 360 ohm and 180 ohm resistor to build a voltage divider. I assume the maximum Vin is 15v and maximum Vout is 5v. I'm afraid the resistor value is low and spoiling the arduino uno. I want to ask is the resistor value safe for arduino?

What are the actual specs for the Solar panel? Most 12V Solar panels will produce around 18V open circuit. Make your resistive divider with larger value resistors, so you arnt wasting power. Something like 4.7K and 1.8K .

mauried: What are the actual specs for the Solar panel? Most 12V Solar panels will produce around 18V open circuit. Make your resistive divider with larger value resistors, so you arnt wasting power. Something like 4.7K and 1.8K .

I don't have the actual spec because I just taking the solar panel from my supervisor. Btw, thanks. I think I just use a bigger resistor

If you use the internal reference of 1.1 volts , you can scale you resistor divider accordingly - say 1k/12k. As the input is still rated at 5v , in this form it can stand a lot of overvoltage . I would build the voltmeter , then calibrate it against your multimeter. The “map” function is useful

Use your multimeter to measure the "open circuit" voltage of the panel in bright sunlight and tell us what that is.

You can use an extra 10K resistor to protect the analog input from overvoltage, like this:

solar_current.png

solar_current.png

Why do you want to know solar panel voltage, loaded with a voltage divider. If you want to know the power a panel produces, or solar irradiation, then you should measure panel CURRENT.

If you want to power an Arduino from a solar panel, then you must have a rechargeable battery in between. In which case battery voltage (not panel voltage) is important. Leo..