voltage sensor

I am using the below voltage divider for voltage sensing. The supply is solar panel connected across the divider.Is it ok if i connect directly to arduino pin wont the current flowing trough the divider damage the arduino analog pin?
Have i to take some precautionary measures?


Other doubt i have is:
I want to power the arduino board externally:
here is the image of my arduino board below.
I know that i need to connect 5V at Vin pin and change the jumper position once i have programmed the arduino.

But can i connect Usb port to external 5V regulated supply?
or can i connect 12 V battery directly to the male slot(like adapter o/p) provided to the right of the board?
which one do i prefer.


I’ve seen better photos. In fact, I am not sure I have seen one worse recently, even those my wife takes as she jabs at the shutter button. :astonished:

You do not connect 5 V to Vin. What jumper? What is this male slot “provided to the right of the board”?

Before we suggest resistor values, you have to tell us what (maximum) voltage your solar cell generates.

You choose the divider so that the output voltage is in the range 0..5V, then no current flows into the pin.

If the lower resistor is about 10k, then even on overload the current would be a fraction of 1mA anyway.

Its recommended to use a divider with an output impedance no larger than 10k, in order to retain full accuracy, so I would generally use a divider with a 10k lower resistor.

If you wanted to reduce the current through the divider even more you could use 100k lower resistor in series with 0.1uF capacitor to keep the output impedance low.

Actually i am using 50K upper resistor,10K lower resistor and 1uf across 10K.