Voltage Measurement with Arduino Documentation

1. Voltage Measurement using Arduino
The voltage measurement using Arduino the input voltage is must in range 0 to
5v. It’s achieved using below circuit. AC voltage is step down with help of
voltage transformer, its primary winding is connected across the supply and its
secondarywinding is connected to voltage divider circuit for reduced further
voltage level.
Voltage sensor circuit

2. Transformer–
Step-down transformer
The step-down converters are used for converting the high voltage into
low voltage. The converter with output voltage less than the input voltage is
called as a step-down converter, and the converter with output voltage greater
than the input voltage is called as step-up converter. There are step-up and step-
down transformers which are used to step up or step down the voltage levels.
230V AC is converted into 12V AC using a step-down transformer. 12V output
of step-down transformer is an RMS value and its peak value is given by the
product of square root of two with RMS value, which is approximately 17V.
Voltage divider1 for step down voltagelevel :-
A voltage divider is a simple circuit which turns a large voltage into a smaller
one. Using just two series resistors and an input voltage, we can create an output
voltage that is a fraction of the input.
Formula of voltage divider is vout = vin *
R1
R1+R2
vin =12
R2 = 100Ω

3. R1 = 10Ω
vout = 12 *
10
10+100
= 1.09
so positive voltage is 1.09 and negative voltage is 1.09.(due to AC voltage)
Voltage divider2 for eliminatingnegativeportionof
AC voltage :-
vin =5
R2 = 470 kΩ
R1 = 470 kΩ
vout = 5*
470
470+470
= 2.5
but this voltage divider directly connected to voltage divider 1.In this
connection resultant voltage is adding.
So resultant voltage at A-B point in positive ac portion is
Voltage divider 1+ Voltage divider 2
= 1.09 + 2.5 = 3.59 ------(1)
And resultant voltage at A-B point in negative ac portion is (due to negative ac
portion Voltage divider 1 output negative)
Voltage divider 1+ Voltage divider 2
= -1.09 + 2.5 = 1.41 -------(2)
Output of equation (1) and (2) are less than 5v and greater than 0v so we
interface to Arduino because of Arduino operating voltage range is 0 to 5 v dc.