Hello I'm trying to use a voltage divider to reduce the voltage from my solar panel (it's a kit) as it can produce a voltage of 7.2 V and I know that the analog pin on a Arduino Mega 2560 is limited from 0 to 5V .
For the circuit I'm using 2 180ohm resistors
The solar panel as the source and the GND of the panel is tied to the GND of the Arduino
When the circuit is operating I'm getting mV readings not what I expect
The solar panel has been outputing 2.6V and I'm expecting on the Vout that it will be 1.3V roughly
Now if I sparate the ground from the Arduino and build the solar panel in conjunction with the voltage divider circuit (so the Arduino ground is separate from the solar panel ground) I'm just reading the full voltage coming out of the solar panel it's not divided.
I'm curious if anybody can help me to get this to work I've been using my meter to measure all this before I damage my Arduino .
Such a low resistance may be loading down the panel, causing voltage to fall. Try two 4.7k resistors. What is the maximum voltage the panel puts out in full sun with nothing connected but the volt meter? What is the size of the panel?
JCA34F:
Such a low resistance may be loading down the panel, causing voltage to fall. Try two 4.7k resistors. What is the maximum voltage the panel puts out in full sun with nothing connected but the volt meter? What is the size of the panel?
So I put in the 4.7k resistors in and I got a bigger mV value now in the 70 mV range
I think I'll bump up the resistance once more
And in full daylight I read 7.18V as my max recorded and the size is 160mm X 70 mm
S1Sanichara:
So I put the panel to a constant light that produced about 4.5v
The first resistor measured about 2.1 volts
The second measure 451mV
So open circuit the panel shows 4.5V?
With 20K of resistance (your two 10K resistors in series) you see 2.1V at the top of the resistor. And with that 2.1V you see 0.45V at the middle of the divider?
It seems like the panel does not produce enough current to feed your resistor divider. When connected to the divider you see its output drops to 2.1V which means the panel has a high output resistance and even a small current draw is enough to produce a drop across it.
Consider putting an op-amp in a voltage-follower configuration between the panel and your resistor divider.