# The Basics

The Arduino analog input is limited to a 5 VDC input.   If you wish to measure higher voltages,  you will need to resort to another means.  One way is to use a voltage divider.    The one discussed here is found all over Amazon and eBay.

It is fundamentally a 5:1 voltage divider using a 30K and a 7.5K Ohm resistor.

Keep in mind, you are restricted to voltages that are less than 25 volts.   More than that and you will exceed the voltage limit of your Arduino input.

# Where to Buy a 25V Voltage Sensor

Its available from the following vendors:

Amazon

AliExpress

# Basic Connection

## Inputs

• GND –  This is where you connect the low side of the voltage you are measuring.   Caution! : This is the same electrical point as your Arduino ground.
• VCC:  The is where you connect the high side of  the voltage you are measuring

## Outputs

• – (or minus):  This connects to your Arduino ground.
• +:  This is not connected.  It does absolutely nothing… zilch… nada… jack diddly doo doo.

# Schematic

The schematic for this is pretty straight forward.  As previously mentioned, its just a couple of resistors.   In fact, you could build your own in a pinch.

# Tutorial

## The Connections

Find yourself a 9 volt battery and connect it,  your voltage sensor module and Arduino as shown below.

## The Sketch

Enter the following sketch, upload it and go to town.   If you open your Arduino serial monitor you will be able to see the voltage.

```/*
DC Voltmeter Using a Voltage Divider
Based on Code Created By
T.K.Hareendran
*/

float vout = 0.0;
float vin = 0.0;
float R1 = 30000.0; //
float R2 = 7500.0; //
int value = 0;
void setup(){
Serial.begin(9600);
Serial.print("DC VOLTMETER");
}
void loop(){
vout = (value * 5.0) / 1024.0; // see text
vin = vout / (R2/(R1+R2));

Serial.print("INPUT V= ");
Serial.println(vin,2);
delay(500);
}

```

1. Nikos February 24, 2019
2. Engidaw June 2, 2018
3. Abdul Goffar Al Mubarok January 27, 2018
4. capnfatz@gmail.com December 31, 2017
5. Julian December 30, 2017
6. hajir March 17, 2017
7. capnfatz@gmail.com January 10, 2017