 duino , DIY Projects

Interfacing ACS712 Current Sensor

with Arduino – Measure Current with
Arduino
 July 19, 2018
 By Administrator

In this project, we will discuss about ACS712 Current Sensor, how a Hall
Effect based current sensor works and finally how to interface the ACS712
Current Sensor with Arduino.

Outline
 Introduction
 Output Video
 A Brief Note on ACS712 Current Sensor
o How ACS712 Current Sensor Works?
 o ASC712 Current Sensor Application Circuit
 ACS712 Current Sensor Module
 Interfacing ASC712 Current Sensor with Arduino
 Circuit Diagram of ASC712 Current Sensor with Arduino
o Components Required
o Circuit Design
 Code
 Working
 Applications

Introduction

If you recall the previous Arduino project, I have discussed about measuring
voltages greater than 5V with Arduino using a Voltage Sensor. In this
project, we will learn about measuring current using a Current Sensor
(ACS712 Current Sensor to be specific).

A Current Sensor is an important device in power calculation and

management applications. It measures the current through a device or a
circuit and generates an appropriate signal that is proportional to current
measured. Usually, the output signal is an analog voltage.

Output Video

Take a look at the output video before proceeding further into ACS712
Current Sensor Module.

A Brief Note on ACS712 Current Sensor

The ACS712 Current Sensor is a product of Allegro MicroSystems that can be
used for precise measurement of both AC and DC currents. This sensor is
based on Hall Effect and the IC has an integrated Hall Effect device.

Coming to the output of the ACS712 Current Sensor, it produces an analog

voltage that is proportional to AC or DC currents (whichever is being sensed).

The ACS712 IC is available in an 8-lead SOIC package and the following image
shows its pin diagram.

Let us now see the pin description of ACS712. The following table shows the
pin number, name and description.
 Pin Number Pin Name

1&2 IP+ +ve term

3&4 IP- -ve term

5 GND

6 FILTER External Cap

7 VIOUT

8 VCC

There are three variants of ACS712 Sensor based on the range of its current
sensing. The optimized ranges are +/-5A, +/-20A and +/-30A. depending on
the variant, the output sensitivity also varies as follows:

ACS712 Model Optimized Current Range

ACS712 ELC-05 +/- 5A

 ACS712 ELC-20 +/- 20A

ACS712 ELC-30 +/- 30A

How ACS712 Current Sensor Works?

As mentioned earlier, the ASC712 is based on Hall Effect. There is a copper

strip connecting the IP+ and IP- pins internally. When some current flows
through this copper conductor, a magnetic field is generated which is sensed
by the Hall Effect sensor.

The Hall Effect sensor then converts this magnetic field into appropriate
voltage. In this method, the input and the output are completely isolated.
ASC712 Current Sensor Application Circuit

The typical application circuit using the ASC712 Current Sensor is given in its
datasheet and the following images shows the same.

ACS712 Current Sensor Module

Using one of the variants of the ACS712 IC (5A, 20A or 30A), several
manufacturers developed ASC712 Current Sensor Module boards that can be
easily interfaced to a microcontroller like Arduino.

The following image shows the ASC712 Current Sensor board used in this
project.
As you can see, it is fairly a simple board with only a few components
including the ASC712 IC, few passive components and connectors.

This particular board consists of ASC712 ELC-30 i.e. the range of this board is
+/- 30A. the following image shows the components and pins on the board.

Interfacing ASC712 Current Sensor with Arduino

Measuring voltages (DC Voltages) with Arduino is very easy. If your
requirement is to measure less than or equal to 5V, then you can directly
measure using the Arduino Analog Pins. If you need to measure more than
5V, then you can use a simple voltage divider network or a voltage sensor
module.

When it comes to measuring current, Arduino (or any other microcontroller)

needs assistance from a dedicated Current Sensor. So, Interfacing an ACS712
Current Sensor with Arduino helps us in measuring current with the help of
Arduino.

As ASC712 can be used for measuring either AC or DC currents, Arduino can

be implemented to measure the same.

Circuit Diagram of ASC712 Current Sensor with Arduino

The circuit diagram of interfacing ACS712 Current Sensor with Arduino is

shown in the following image.
Components Required

 Arduino UNO [Buy Here]

 ASC712 Current Sensor Module
 Load (like a lamp or a motor)
 Power supply (for load like battery)
 16×2 LCD Display [Buy Here]
 10KΩ Potentiometer
 330Ω Resistor
 Connecting wires

Circuit Design

First, the load. I have used a 12V DC Motor along with a 12V power supply.
The screw terminals of the ASC712 Current Sensor Module board are
connected in series with the motor and power supply as shown in the circuit
diagram.

Then connect the VCC, GND and OUT of the ASC712 board to +5V, GND and
A0 of Arduino.
Now, in order to view the results, a 16×2 LCD is connected to Arduino. Its RS,
E, D4-D7 pins are connected to Digital I/O Pins 7 through 2 of Arduino.

A 10KΩ POT is connected to Pin 3 of LCD and its VCC and GND are connected
to +5V and GND.

Code
#include <LiquidCrystal.h>

LiquidCrystal lcd(7, 6, 5, 4, 3, 2);

const int currentPin = A0;

int sensitivity = 66;
int adcValue= 0;
int offsetVoltage = 2500;
double adcVoltage = 0;
double currentValue = 0;

void setup()
{
Serial.begin(9600);
lcd.begin(16, 2);
lcd.print(" Current Sensor ");
lcd.setCursor(0,1);
lcd.print(" with Arduino ");
delay(2000);
}

void loop()
{
adcValue = analogRead(currentPin);
adcVoltage = (adcValue / 1024.0) * 5000;
currentValue = ((adcVoltage - offsetVoltage) / sensitivity);

Serial.print("Raw Sensor Value = " );

Serial.print(adcValue);

lcd.clear();
delay(1000);
//lcd.display();
lcd.setCursor(0,0);
lcd.print("ADC Value = ");
lcd.setCursor(12,0);
lcd.print(adcValue);

delay(2000);

Serial.print("\t Voltage(mV) = ");

Serial.print(adcVoltage,3);

lcd.setCursor(0,0);
lcd.print("V in mV = ");
lcd.setCursor(10,0);
lcd.print(adcVoltage,1);
 delay(2000);

Serial.print("\t Current = ");

Serial.println(currentValue,3);

lcd.setCursor(0,0);
lcd.print("Current = ");
lcd.setCursor(10,0);
lcd.print(currentValue,2);
lcd.setCursor(14,0);
lcd.print("A");
delay(2500);
}

view rawArduino_Current_Sensor_ACS712.ino hosted with ❤ by GitHub

Working

Make the connections and upload the code to Arduino. In the code, there is a
small calculation for measuring the current.

First, assuming the VCC to ASC712 is 5V, when there is no current flowing
through the IP+ and IP- terminals, the output voltage at VIOUT of ACS712 is
2.5V. This means that you need to subtract 2.5V from the voltage measured
at the analog pin.

Now, in order to calculate the current, divide this value with the sensitivity of
the sensor (185mV/A for 5A Sensor, 100mV/A for 20A Sensor and 66 mV/A for
30A Sensor).

The same is implemented in code as follows.

adcValue = analogRead(currentPin);

adcVoltage = (adcValue / 1024.0) * 5000;

currentValue = ((adcVoltage – offsetVoltage) / sensitivity);

Applications

The ACS712 Current Sensor can be used in various current measuring

applications like:

 Inverters
 SMPS
 Battery Chargers
 Automotive Applications like Inverters, Power Steering etc.