Is it possible to configure the Arduino to give me 0-10V analog input?
I realize that I can use a voltage divider. I was just wondering if I can use a larger range for the analog input.
Electronic – Arduino Mega 0 – 10V analog input
analogarduinoinput
Related Solutions
Take a look at the chart on page 260 of the datasheet. ADCON1 is the register I believe you want to take a look at.
With a sketch, read and print a known test voltage of a little bit less than your reference voltage, say 1.5V in this case. The printed result will be the same fraction of 1024 that your test voltage is of the reference voltage, or:
V_test x
------ = ----
V_ref 1024
1024
V_ref = ---- V_test
x
Edit: The intent here was to supply a presumed 2.0V external analog reference, say it's your 20K resistor. Now supply a known voltage of ~80% the 2V reference to one of the MCU's analog inputs. Run a sketch to print what the MCU reads as that voltage as. Calculate the actual analog reference voltage as I did above. If it is 2.0V, you're done.
This is how I'd make a 2.0V ARef. An AtMega328p's ARef only draws ~100μA at Vcc = 3.3V, so this should still be pretty close:
simulate this circuit – Schematic created using CircuitLab
As above, get A/D reading of the known voltage input and calculate what the reference voltage must be, to confirm it.
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Best Answer
Input voltages can be "scaled" down to suit the Arduino's ADC input voltage range.
As Oli says, a 10V input can be scaled down with a potential divider.
In its most basic form this can be two resistors.
As shown below, the input current flows through R1 and through R2.
Voltage drop across a resistor = V = I x R
As both resistors carry identical current (= input current)
the voltage drop across each resistor is proportional to the resistor value
So, if R1 = R2 then the the voltage across each is equal so they each drop half the input voltage.
In the general case - input voltage is across R1+R2. Output voltage is across R2 only. So Vout = Vin x R2 / (R1 + R2)
ie the division ratio = R2 / (R1 + R2)
When R1 = R2 the division ratio is 1/2 so
a 0-10V input will be reduced to o-5 volts.
R1 and R2 can be typically 10k ohms each in this case.
Much larger values can be used but they can affect the conversion accuracy. eg 100k + 100k.
Usually it is wise to limit R2 to not more than about 20k ohm.