# Measure voltage from solar panel

Hy everyone!

I'm working on a homeproject where I want to measure the voltage of a solar panel with my arduino uno.
So, I've done the basic tutorial with the arduino as the power source and a potenitiometer as a resistor. It worked like charm!
But then I realized, that my solar panel Open Circuit voltage is 22.50V (It's an 80W panel with 22.50V Open cicuit voltage and 4.69A Short circuit current).
I'm a total noob when it comes to electric circuits and it's accessories so I'd like to ask for your help.
So the question is, what resistors and other stuff do I need to measure the voltage of the panel and keeping my arduino safe at the same time?
Can I still use my 100kohm potentiometer or do I need something bigger?

You need to use a voltage divider. I suggest a 10K resistor from the analog input pin to ground, and a 47K resistor from the pin to the positive side of the solar panels. That will give you (10/(10+47)) * 22.5 = 3.95V at the pin when the panels are producing 22.5V.

Thx for the quick answear!
Do I need to bother with the negative side of the panel?

The negative side of the panel needs to be connected to Arduino ground. Is that permissible? What will the solar panel be powering?

Well... it won't power anything.
I just want to measure it's produced voltage. Do I need a power consumer in that case too?

Mark5217:
Well... it won't power anything.
I just want to measure it's produced voltage. Do I need a power consumer in that case too?

No, I just wanted to know if there was any reason you couldn't connect the negative side of the panel to ground.

Do I need a power consumer

What does measuring the Open Circuit Voltage tell you ?
Depending on the sunshine intensity you will "always" measure about 20V, but can draw between 0 and 4A ( 80W = 4A*20V, a bit simplified)

I knew that that W=V*A . So I know it will always show about 20 V.
I don't really know what does it tell you.