# Arduino Voltage Divider

So am doing a project which involves the reading of voltage and current generated by Solar Panel. Now I learnt that Arduino cant Read Voltage directly above 5V. To read above that you need to add a voltage divider circuit in between. But that's the great solution for a solar panel around 20W. Now what if i want to read voltages of n number of solar panels which are in a farm in which each solar panel generated around 300-400 W . 1)Will adding voltage divider help? 2) What is the limit of Arduino of Voltage Divider? 3) What registers i would have to use for such big voltage divider?

• Are you a electrical engineer and familiar with high voltages and high currents? When you have to ask this question, you better not mess with the solar panels. The solar power inverter has probably a way to get those numbers via a website or a interface.
– Jot
Jan 11, 2018 at 15:55
• @Jot no am not an electrical engineer. I do not the how u work with high voltages and current. Jan 30, 2018 at 9:59

You will need n voltage dividers, one for each solar panel.

2) What is the limit of Arduino of Voltage Divider?

There is a limit on the equivalent Thévenin resistance of the voltage source connected to the Arduino analog inputs. It should be no larger that 10 kΩ, otherwise you risk cross-talk between the channels.

If the solar panels have a low output resistance, then the equivalent Thévenin resistance is the resistance resulting from setting the two resistors of the divider in parallel. Setting the smallest resistance to 10 kΩ will ensure you meet the condition while at the same time keeping the consumed current quite low.

There is also a limit on the number of solar panels that you can independently monitor: 16, which is the number of analog inputs on the Mega.

[...] each solar panel generate[s] around 300-400 W

The power generated is irrelevant: only the voltage is a concern. Your dividers must output no more than 5 V.

1) Will adding voltage divider help?

Yes.

2) What is the limit of Arduino of Voltage Divider?

The Arduino has no relevance here. You can build voltage dividers to convert thousands or millions of volts down to 5V if you need to.

3) What registers i would have to use for such big voltage divider?

I guess you mean "resistors" here, not "registers"...

Resistors that give no more than 5V out at the peak voltage of the solar panels, and have a high enough voltage tolerance for the maximum voltage across any one resistor.