# Complete Guide How to Creating a Single-Cell Battery Tester using Arduino

In this project, I will show you a Complete Guide on How to Creating a Single-Cell Battery Tester using Arduino step by step complete process.

Although the popularity and usage of cell batteries have declined, most people still have a few devices around the house that utilize AA, AAA, C, or D cell batteries, such as remote controls, clocks, or children’s toys. These batteries take much less than 5 V, so we can measure a cell’s voltage with our Arduino to determine the state of the cell. Interested.

## ≡ Goal

Single-cell batteries such as AAs normally begin at about 1.6 V if new and then decrease with use. We will measure the voltage and display the battery status visually with LEDs. We’ll apply the reading from analogRead() and then convert the reading to volts. The highest voltage that can be read is 5 V, so we divide 5 by 1,024 (the number of possible values), which equals 0.0048.  if analogRead() returns 512, then we multiply that reading by 0.0048, which equals 2.4576 V.

## ≡ Algorithm

The algorithm for our battery tester work: Read it from analog pin zero. Increase the reading by 0.0048 to build a voltage value. If the voltage is larger than or equal to 1.6 Volt, then quickly turn on a green LED.  the voltage is larger than 1.4 Volt and less than 1.6 Volt, then quickly turn on a yellow LED. If the voltage is less than 1.4 Volt, then briefly turn on a red LED.

## ≡ Hardware Single-Cell Battery Tester using Arduino

what you’ll need to create this project:

1.  560 Ω resistors
2.  2.2 kΩ resistor
3.  green LED
4.  yellow LED
5.  red LED
6.  breadboard Various connecting wires One Arduino and USB cable

## ≡ Sketch Single-Cell Battery Tester using Arduino

```#define newLED 2  // green LED  'new'
#define okLED  4  // yellow LED 'ok'
#define oldLED 6  // red LED    'old'

int analogValue = 0;
1 float voltage = 0;
int ledDelay = 2000;

void setup()
{
pinMode(newLED, OUTPUT);
pinMode(okLED, OUTPUT);
pinMode(oldLED, OUTPUT);
}

void loop()
{
3   voltage = 0.0048*analogValue;
4   if ( voltage >= 1.6 )
{
digitalWrite(newLED, HIGH);
delay(ledDelay);
digitalWrite(newLED, LOW);
}
5   else if ( voltage < 1.6 && voltage > 1.4 )
{
digitalWrite(okLED, HIGH);
delay(ledDelay);
digitalWrite(okLED, LOW);
}
6   else if ( voltage <= 1.4 )
{
digitalWrite(oldLED, HIGH);
delay(ledDelay);
digitalWrite(oldLED, LOW);
}
}```

the Arduino uses the value measured by analog pin 0 at 2 and converts this to a voltage at 3. You’ll read about a new type of variable, float at 1. You’ll also examine some familiar code, such as the if-else functions, and some new topics, such as doing arithmetic and applying comparison operators to compare numbers, which are all explained in the parts that follow.

## ≡ Doing Arithmetic with an Arduino

Simple calculator, the Arduino can perform calculations for us, such as multiplication, division, addition, and subtraction. Here you can see some examples:

```a = 100;
b = a + 20;
c = b - 200;
d = c + 80; // d will equal 0```

## ≡ Float Variables

If you require to deal with numbers with a decimal point, you can apply the variable type float. The values that can be stored in a float fall between 3.4028235 × 1038 and −3.4028235 × 1038, and are usually limited to six or seven decimal places of precision.  you mix integers and float numbers in on your calculations. you could add the float number f to the integer a then store it as the float variable :

```int a = 100;
float f;
float g;

f = a / 3; // f = 33.333333
g = a + f; // g = 133.333333```

## ≡ Comparison Operators for Calculations

We applied comparison operators such as == and != with if statements and digital input signals. In addition to these operators, we can also apply the following to compare numbers or numerical variables:

< less than > greater than

<= less than or equal to >= greater than or equal to

We’ve worked these comparison operators to compare numbers in lines 4, 5, and 6 in the sketch.

## ≡ Improving Analog Measurement Precision with a Reference Voltage

The analogRead() function returns a value equal to a voltage between 0 and 5 V. The higher value (5 V) is the reference voltage, the highest voltage that the Arduino analog inputs will receive and return the highest value for (1,023).

To enhance precision while reading even lower voltages, we can utilize a lower reference voltage. For example, if the reference voltage is 5 V, analogRead() represents this with a value from 0 to 1,023.  if we require to measure only a voltage with a maximum of (for example) 2 V, then we can alter the Arduino output to represent 2 V using the 0–1,023 value range to allow for more precise analysis. You can do this with either an outer or internal reference voltage, as discussed next.

## ≡ Using an External Reference Voltage

The first plan of applying a reference voltage is with the AREF (analog reference) pin, as shown in Figure 2.

We can include a new reference voltage by connecting the voltage into the AREF pin and the matching GND to the Arduino’s GND. Note that this can lower the reference voltage but will not raise it, because the reference voltage attached to an Arduino Uno must not exceed 5 V. A simple method to set a lower reference voltage is by building a voltage divider with two resistors, as shown in Figure 3.

The values of R1 and R2 will define the reference voltage according to the following formula:

Vout is the reference voltage, and Vin is the input voltage—in this case, 5 V. R1 and R2 are the resistor values in ohms.

The most simplistic way to divide the voltage is to split Vin in half by setting R1 and R2 to the same value—for example, 10 kΩ each. If you’re doing this, it’s enough to work the lowest-tolerance resistors you can find, such as 1 percent; confirm their true resistance values with a multimeter, and apply those confirmed values in the calculation.  it’s also a very good idea to place a 100 nF capacitor within AREF and GND to avoid a noisy AREF and prevent unstable analog readings.

If utilizing an outside reference voltage, insert the following line in the void setup() section of your sketch:

`analogReference(EXTERNAL); // select AREF pin for reference voltage`

## ≡ Using the Internal Reference Voltage

The Arduino Uno also has an internal 1.1 V reference voltage. If this meets your wants, no hardware changes are needed. Just add this line to void setup():

`analogReference(INTERNAL); // select internal 1.1 V reference voltage`

## ≡ Variable Resistor

Variable resistors, also known as potentiometers, can usually be adjusted from 0 Ω up to their rated value. Their schematic symbol is shown in Figure 5.

Variable resistors have three pin connections: one in the center pin and one on each side. As the shaft of a variable resistor turns, it increases the resistance within one side and the center and decreases the resistance between the center and the opposite side.

Variable resistors are open as linear and logarithmic. The resistance of linear rules changes at a constant rate when turning, while the resistance of logarithmic models changes slowly at first and then increases rapidly. Logarithmic potentiometers are utilized more often in audio amplifier circuits, because they model the human hearing response. Most Arduino projects apply linear variable resistors such as the one shown in Figure 6.

You can also get small versions of variable resistors, known as trimpots or trimmers (see Figure 7). Because of their size, trimpots are more helpful for making adjustments in circuits, but they’re also very helpful for breadboard work because they can be slotted in.